Classifications

• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
  • G09B19/00—Teaching not covered by other main groups of this subclass
  • G09B19/04—Speaking
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/11—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for measuring interpupillary distance or diameter of pupils
  • A61B3/112—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for measuring interpupillary distance or diameter of pupils for measuring diameter of pupils
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/40—Detecting, measuring or recording for evaluating the nervous system
  • A61B5/4076—Diagnosing or monitoring particular conditions of the nervous system
  • A61B5/4088—Diagnosing of monitoring cognitive diseases, e.g. Alzheimer, prion diseases or dementia
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
  • G09B19/00—Teaching not covered by other main groups of this subclass
  • G09B19/06—Foreign languages

Definitions

• This invention relates generally to the field of cognitive and linguistic assessment methods and relates more particularly to methods for assessing cognitive and linguistic abilities by measuring the pupil sizes of a patient in response to predetermined verbal and/or visual stimuli.
• Cognitive and linguistic abilities in individuals can be assessed and studied using a variety of well-known constructs, such as thorough testing of linguistic comprehension, semantic associative priming, working memory, and attention.
• traditional clinical and research measures associated with such constructs are fraught with methodological limitations and "confounds,” thus reducing the validity and generalization of findings, especially with regard to people with neurological impairments or disorders.
• Confounds are factors that threaten assessment validity. These confounds include comprehension of instructions, memory, motor abilities required for responding, as well as problems of using off-line (summative) measures (those gathered after a task has been completed) as opposed to online measures (those occurring while a person is engaged in a task). These confounds might create inconsistent and/or inaccurate assessment of linguistic comprehension in an individual, especially for individuals with neurological impairments. Neurologically impaired people might or might not have any linguistic comprehension deficits, resulting in disorders such as aphasia.
• this retelling method relies on patients' speech or writing abilities in retelling stories verbally or textually (writing). To accurately assess comprehension, one must rule out the possible response failures or inconsistencies in memory, speech writing, gesture, and other motor activities among individuals, especially for individuals with neurological impairments.
• Hallowell (1999, 2002) discloses an eye-tracking method that involves measuring and tracking individuals' eye fixations in response to visually and/or auditorally presented stimuli.
• the disadvantage of this method is that individuals can control where they fixate their eyes as they look at various components of a visual display.
• an individual is told to look naturally and not control his or her eyes in any particular way, he or she may still try to control where he or she looks so as to respond in a more correct or desirable way.
• the intended purpose of using spontaneous, unplanned movements of the eyes may be spoiled in cases where viewers attempt to control their fixation patterns.
• individuals with ocular motor apraxia have difficulty looking intentionally at images during fixation-based comprehension tasks, further complicating eye fixation-based assessments.
• Pupillometry has been used to test cognitive intensity through the measurement of pupil dilation and constriction, including the technique of task-evoked responses of the pupil (TERPs).
• TRIPs task-evoked responses of the pupil
• non-clinically relevant stimuli such as mental mathematical problems, memory load for words and digits, pitch discrimination, mental arithmetic, letter discrimination, speech shadowing/sentence repetition, sentence comprehension, cross-linguistic interpretation, and forced-choice tasks.
• These non- clinically relevant stimuli cannot provide any clinically useful information about a patient' s actual linguistic comprehension level in order to evaluate whether this individual has any linguistic comprehension deficit, especially if the individual has any neurological impairment.
• Clinical assessment methods should produce useful information about a person's true ability to understand everyday language (indexing language comprehension level in a clinically relevant way).
• Useful information should be information related to how a person normally uses language.
• knowing how much a person understands when listening to others speak is essential for appropriate treatment, socialization, and major life decisions related to living arrangements, financial management, legal status, and potential for return to work, educational, and leisure activities.
• Clinically relevant stimuli are those stimuli related to an individual's everyday functional use of the language that leads to useful information regarding an individual's linguistic comprehension level.
• Non-clinically relevant stimuli are language stimuli related to unusual use of language that will not lead to useful information about a person's language abilities.
• a task-evoked pupillary response is the tendency of a pupil to dilate slightly in response to loads on working memory increased attention, sensory discrimination, or other cognitive loads.
• the pupil dilates more significantly in response to extreme emotional stimulations such as fear, or to contact of a sensory nerve, such as pain.
• Gutierrez and Shapiro (2011) used pupillometry to examine the different effects of relative thematic fit between a verb and its arguments between people with aphasia (PWA) and similarly aged people without aphasia (aged-matched controls).
• PWA aphasia
• Gutierrez and Shapiro's study participants listened to sentences in which the subject and object of the sentence either fit thematically with the verb (plausible sentences) or did not fit thematically with the verb (implausible sentences). In both groups of participants with and without aphasia, implausible sentences elicited greater pupillary dilations than plausible sentences.
• the person being assessed does not need to understand any instructions.
• the device can be in contact with the person being assessed, such as by using a pupilometer (sometimes referred to as "pupillometer") mounted on the head.
• a pupilometer sometimes referred to as "pupillometer”
• a remote device can be used to measure, record and analyze the pupillary response, and the device will not be in contact with the person (although, sometimes, a chin rest may be used to help keep the head relatively stable).
• the methods allow for: stimulus adaptations that may serve to control for perceptual, attentional, and ocular motor deficits in the differential diagnosis of language processing difficulties; reduced reliance on patients' understanding and memory of verbal instructions prior to testing; allowance for a real-time measure of comprehension; and allowance for testing of a broad range of verbal and nonverbal stimulus types.
• An additional advantage of the present invention is that pupillary control is often preserved even in cases of severe motoric and cognitive deficits, therefore the present invention has the sensitivity and consistency to assess the individual's linguistic comprehension to yield clinically useful data as to the level of the linguistic comprehension, if any impairment exists, and the level of linguistic impairments.
• pupillometry over eye fixation analysis alone include that viewers are not able to consciously control their own pupil size. Given that pupil size is controlled subcortically and automatically through the reticular activating system in the brainstem, confounds associated with intentional conscious control of the eyes that may occur when monitoring fixations are not possible when using pupillometry.
• the present invention provides methods for assessing a patient's linguistic comprehension using a pupillary response system (also called "pupillary system”), especially for patients with neurological disorders or impairments.
• the pupillary system includes at least one pupillometer configured to measure the patient's pupil response to index linguistic comprehension according to the varied difficulty levels of the verbal stimuli.
• a pupillometer is defined as any instrument for measuring the width and/or the diameter of the pupil.
• a first of the inventive methods is directed toward the assessment of linguistic comprehension using verbal stimuli.
• a list of verbal stimuli is first selected, which is separated into at least two sets of stimuli.
• Each set of stimuli includes one or more verbal stimuli in the list; the two sets of the verbal stimuli differ substantially from each other in terms of the difficulty level.
• the verbal stimulus for the present inventive method preferably includes one or more words, one or more sentences, or combinations or mixtures thereof.
• the verbal stimulus includes one or more words, with a single noun being the most preferred.
• the difficulty level of the word is based on one or more difficulty criteria, including, but not limited to, age of acquisition, word frequency, familiarity, naming latency, other similar factors, or combinations thereof. Other similar factors can include the length of the word, different pronunciation of the word, and perceived difficulty level.
• the perceived difficulty of the verbal stimuli can be evaluated by asking the patient to sort the verbal stimuli into two different levels: one is relatively easy, while the other is relatively difficult. It is contemplated that other methods of evaluating the difficulty levels can also be used so long as these methods provide relatively reliable information about the perceived difficulty of the verbal stimuli.
• a clinician presents the patient with one verbal stimulus at a time from the list of verbal stimuli (the assessment task), and then the patient's pupillary response data during the presentation of each stimulus are measured and recorded for a period of time ranging from about 200 milliseconds to about 10 seconds.
• the clinician instructs the patient to look at a fixation point during the presentation of each verbal stimulus.
• a clinician preferably administers to the patient one or more comprehension tests during the presentation of the verbal stimuli.
• the pupillary response data for all stimuli are analyzed and interpreted to assess the patient's linguistic comprehension in terms of the difficulty levels of the stimuli.
• the patient's pupillary response data can then be compared to the normative data, the normative data being pupillary response data of known healthy individuals to the same verbal stimuli. If the patient's pupillary response data are significantly different from the normative data, then this is a good indicator that the patient has a linguistic comprehension deficit.
• the method is capable of assessing the linguistic comprehension level of neurologically impaired patients.
• the impairment severity of the patient is preferably evaluated prior to the starting of the assessment tasks, such as presenting the stimuli to the patient.
• a baseline test is preferably administered to the patient, and the patient's pupillary response data during the baseline test is measured and recorded (called the baseline measures or values).
• the baseline measures can then be incorporated into the analysis of the pupillary response data for the assessment task to eliminate the impact of emotional factors on the pupillary response.
• the verbal stimuli are presented to the patient audibly to assess the patient's auditory comprehension level.
• auditory presentation can avoid many distracting factors associated with textual presentation (also visual presentation) to give a more accurate analysis of the pupillary response as related to linguistic cognitive efforts associated with varying difficulty levels of verbal stimuli.
• the verbal stimuli are presented to the patient textually to assess the patient's reading comprehension level.
• the verbal stimulus includes one or more sentences, with a single sentence being the most preferred.
• the difficulty level of the sentence is determined according to one or more criteria.
• the suitable criteria include, but are not limited to, sentence length, sentence branches, number of verbs, number of imbedded clauses, other similar factors, or combinations or mixtures thereof.
• the pupillary responses include pupil diameter, maximum pupil diameter, time to maximum pupil diameter, average pupil diameter, and/or other similar data.
• a second of the inventive methods is directed toward the assessment of linguistic comprehension using the combination of visual and verbal stimuli.
• a list of verbal stimuli is first selected, which comprises at least two sets of verbal stimuli of substantially different difficulty levels.
• the visual stimuli are then selected, in which each visual stimulus includes an image that corresponds to the verbal stimulus in the verbal stimuli list. Further, the visual stimuli are preferably designed to minimize the presence of distracting visual features.
• a clinician presents each pair of visual and verbal stimuli to the patient in the following manner: a visual stimulus is presented to the patient at the same time as or immediately after presenting each verbal stimulus, the visual stimulus comprising at least one image that corresponds to the verbal stimulus being presented at the same time or immediately prior to the said visual stimulus.
• the visual stimulus is preferably presented on a computer monitor screen.
• the pupillary responses of the patient are measured and recorded during the presentation of each stimulus. After the completion of the assessment task (all stimuli are presented to the patient), the pupillary response data are analyzed and interpreted to assess the patient's linguistic comprehension illustrated in the first of the inventive methods.
• one or more foil trials are at times preferably administered to the patient.
• the foil trial includes the steps of presenting the patient with a foil stimulus at the same time as or immediately after presenting a verbal stimulus as illustrated in Figs. 9 (steps 94 to 95) and 11 (steps 114 to 115).
• the foil trial comprises one or more images that do not correspond to the verbal stimulus being presented at the same time or immediately prior to the foil stimulus.
• the foil trial can be repeated at one or more intervals as needed.
• the method may comprise about 10% to 30% of foil trials.
• the clinician may preferably present one or more filler stimuli to the patient to substantially reduce or prevent the pupillary changes in the patient due to any potential abrupt change in luminance between the stimuli.
• the methods in the present invention preferably use pupillary response systems that are suitable for purposes of the present invention.
• the pupillary response system preferably includes a near infrared light and processing software, and more preferably with a video camera.
• the processing software is capable of identifying, measuring, recording, and analyzing the patient's pupillary response data, such as pupil center, pupil diameter, maximum pupil diameter, average pupil diameter, latency time to maximum pupil diameter, and/or other similar data.
• the clinician preferably administers hearing and/or vision screenings to the patient prior to presenting the patient with any stimuli (see Fig. 2).
• Fig. la is a flowchart illustrating a broad embodiment of the method of the present invention for using verbal stimuli to assess linguistic comprehension.
• FIG. 1 is a flowchart illustrating a more preferred embodiment of the method of Fig. la.
• FIG. 2 is a perspective view illustrating a patient seated in front of a computer monitor during testing using the pupillary methods of the present invention.
• FIG. 3 is a flowchart illustrating a more preferred embodiment of the method of Fig. la, in which a baseline test is administered.
• Fig. 4 is a flowchart illustrating a broad embodiment of the method of the present invention for using visual and verbal stimuli to assess linguistic comprehension.
• Fig. 5 is an illustration of a sample visual stimulus used in the method for testing linguistic comprehension of the present invention. This image is presented simultaneously with a corresponding word.
• Fig. 6 is an illustration of a sample foil visual stimulus used in the method for testing linguistic comprehension of the present invention. This image was presented simultaneously with a non-corresponding word as specified in the foil stimulus protocol.
• Fig. 7 is an illustration of a sample image of a filler stimulus used in the method for testing linguistic comprehension of the present invention. This filler stimulus image was displayed for about three seconds between each experimental stimulus item.
• Fig. 8 is a flowchart illustrating a portion of a preferred embodiment of the method of Fig. la, in which the comprehension test is administered to keep the patient focus on the assessment test.
• Fig. 9 is a flow chart illustrating a portion of a preferred embodiment of the preferred embodiment of the method of Fig. 4, in which a foil stimulus test is administered.
• Fig. 10 is a flow chart illustrating a portion of a preferred embodiment of the preferred embodiment of the method of Fig. 4, in which a filler stimulus is administered.
• Fig. 11 is a flow chart illustrating a portion of a preferred embodiment of the preferred embodiment of the method of Fig. 4, in which both foil stimulus test and filler stimulus are administered.
• the present invention is a method for assessing a patient's linguistic comprehension using a pupillary response system (also called "pupillary system”), especially for patients with neurological disorders or impairments.
• the pupillary system includes at least one pupilometer configured to measure the patient's pupil response to index linguistic comprehension according to the varied difficulty levels of the verbal stimuli.
• pupilometer also called “pupillometer”
• Pupilometers may comprise hand-held units, head-mounted units, units with a chin rest, remote units, other similar units, or combinations thereof so long as they are suitable for the purposes of the present invention.
• the individual to be assessed of his or her linguistic comprehension skill or level can be referred to as "patient” or “participant.”
• patient or "participant.”
• the person executing the assessment method on a patient is referred to as “researcher” or “clinician.”
• suitable verbal stimuli are words or sentences of varying difficulty levels as discussed in detail below.
• a broad embodiment of the present invention is a method including the steps of (1) selecting or compiling a list of verbal stimuli with at least two sets of verbal stimuli of substantially different difficulty levels; (2) presenting to the patient one stimulus at a time from the list of stimuli in a random order or a set order; (3) measuring and recording the patient's pupil response data; (4) repeating steps 2 and 3 until all stimuli from the list are presented to the patient; and then (5) analyzing and interpreting the pupil response data for all stimuli to assess the patient's linguistic comprehension.
• the pupil response data are preferably compared to the data collected for people without any neurological disorder, and the differences in the response can indicate whether or not the patient has any linguistic impairment and/or the degree of the impairment.
• FIG. 1 A preferred inventive method of the present invention is illustrated by Fig.
• hearing and vision screenings are administered to the patient 12.
• the selected patient is then positioned in front of a screen 13 followed by configuring the pupillary response system to measure the patient's pupillary response 14.
• the configuration of the pupillary response system 14 can be done prior to the step 13 of positioning the patient.
• the list of stimuli from step 11 is then presented to the patient one stimulus at a time 15, during which the pupillary response data are measured and recorded for each verbal stimulus 16. Steps 15 and 16 are repeated 15a until all suitable stimuli in the list are presented to the patient, and then the pupillary response data are analyzed and interpreted 17 for all verbal stimuli to assess the patient's linguistic comprehension level.
• a suitable list of verbal stimuli is selected according to the varied stimuli levels of the verbal stimuli.
• the verbal stimuli have at least two sets of verbal stimuli, in which the two sets of the verbal stimuli differ substantially from each other in terms of the difficulty level.
• Each set of the verbal stimuli has one or more verbal stimuli.
• Significantly differing levels of difficulty in the verbal stimuli can result in different cognitive efforts exerted by the patient, which translate into different pupillary responses in terms of comparative changes in the pupillary diameters. These pupillary responses are measured and recorded by the pupil response measurement system, and analyzed to assess the patient's linguistic comprehension.
• the present method is sensitive enough to test even slight differences in pupillary responses with regard to the cognitive efforts exerted for different difficulty levels of verbal stimuli.
• the present method is capable of assessing a person's linguistic comprehension level to see if that patient has any linguistic comprehension deficit, substantially reducing confounds associated with the traditional assessment method.
• More than two sets of verbal stimuli can be used so long as the difficulty levels between the sets of stimuli are substantial and/or significant, ensuring that substantially different cognitive efforts are being exerted on each set of stimuli, resulting in substantially different pupillary response in a patient.
• the two sets of verbal stimuli are used with one set of verbal stimuli being substantially relatively difficult stimuli, and the other set of verbal stimuli being substantially relatively easy.
• the suitable verbal stimuli include words or sentences of varying difficulty levels (see details of stimuli selection in the section of STIMULI SELECTION).
• the verbal stimulus is one or more words.
• the verbal stimulus is one word, in which case the method includes two sets of words and/or sentences, one set of words and/or sentences are substantially more difficult than average, while the other set of words and/or sentences are substantially easier than average words.
• the patient's responses to the two sets of words such as the responsive changes of his or her average pupil diameter, can then be compared to that of the average pupil responses from individuals without any neurological disorder to evaluate whether or not the patient has any linguistic impairment, and even to determine the extent of the patient's linguistic comprehension impairments.
• the criteria and/or methods of selecting and compiling the verbal stimuli are discussed in detail hereinbelow.
• a patient to be tested is preferably required to pass a vision and/or a hearing screening 12 as shown in Fig. 1.
• Other screenings can also be administered, such as pupillary response, to ensure that the patient is a suitable individual for using the present inventive method.
• the vision screening is optionally or preferably administered to demonstrate the patient's vision acuity is appropriate for reading text or visual image on a computer screen or monitor at a suitable distance (preferably about 20-30 inches), with the exact distance dependent upon the size of visual stimuli and the type of screen on which the visual stimuli will be presented to the patient during assessment tasks, as is described in detail below. Glasses or contact lenses can be used if necessary for corrected vision.
• the patient is preferably or optionally also required to pass a hearing screening to demonstrate appropriate hearing acuity for 500-, 1000-, and 2000-Hz pure tones at 65 dB or 25 dB, or other suitable levels. If the patient fails to pass the visual and/or hearing screenings, he or she is preferably excluded from further testing, or the procedure is modified to accommodate the disability.
• additional screening methods may include a standard central visual acuity screening, a color vision screening, a peripheral visual acuity screening, a screening for intactness of the patient's retina, a pupillary examination, ocular motility testing, and an examination of the patient's eyes for swelling, redness, drainage and lesions that may interfere with eye tracking (described below).
• the information from the screening methods is not used to exclude a patient from the testing; instead the information is used to document any deviance from the normal in order to examine for possible effects on the pupillary response data from the testing.
• the next step 13 (Fig. 1) of the inventive method is positioning the patient in front of a screen as shown in Fig. 2.
• a suitable pupillary response system is then configured 14 to measure the patient's pupillary responses.
• the patient 21 is positioned in front of a conventional computer monitor 23 in a comfortable, seated position.
• the screen can be a board, a piece of paper, or a computer screen or monitor, or other suitable surfaces on which the text of the verbal stimuli and/or the visual stimuli can be presented to the patient for purposes of the inventive method.
• the suitable pupillary response system should include at least one suitable pupilometer to measure the patient's pupil response.
• the key feature of the pupilometer is that it should be capable of measuring the patient's pupil response (pupil diameter etc.) frequently without unduly distracting the patient.
• the pupillary measurements are preferably obtained in an unobtrusive way so as to avoid adding any non-cognitive related stimulation to the participants.
• the pupilometer should be positioned so as to provide consistent measurements. Hand-held units might provide high precision (if correctly used) but it might be cumbersome to use and annoying to the patients and/or clinicians. Similarly, the head- mounted pupilometer or camera might provide higher precision but can be bothersome to the patients. In addition, care must be taken with head mounted pupilometer to keep the head band from slipping.
• the head-mounted units, units with chin rests, or remote units are preferred choices, with the remote units being the most preferred.
• the remote units that employ desktop or display-mounted camera are more preferred because they eliminate the need for distracting head- mounted cameras or chin rests.
• a pupilometer may measure the pupil size in several different ways. One way is through a series of graduated filled circles whose sizes are compared with the pupil. The more preferred way is through the use of corneal reflection technology (also called corneal reflection photography or video photography). In using the corneal reflection technology, pupilometers are often combined with eye tracking techniques to ascertain the pupil diameter, the eye movement and the gaze direction.
• corneal reflection technology also called corneal reflection photography or video photography.
• pupilometers are often combined with eye tracking techniques to ascertain the pupil diameter, the eye movement and the gaze direction.
• Corneal reflection technology is a non-contact, optical method.
• the preferred pupilometer comprises one or more image capturing means, one or more illuminators, and image and/or data processing software.
• the image capturing means can be a camera, or a video camera, or other optical or image sensor.
• the illuminator can be a near infra-red light source, preferably near infra-red light emitting diodes (LED). Light from these illuminators, invisible to the human eye, creates reflection patterns on the cornea of the eyes. At high sampling rates, one or multiple images or optical sensors register the image of the patient's eyes.
• image processing software is used to find the eyes, detect the exact position of the pupil and/or iris, and identify the correct reflections from the illuminators and their exact positions.
• the equipment often must be calibrated prior to actual measurements in order to obtain certain actual physiological features of the eyes, such as the radius of the curvature of the eye's cornea and the angular offset between the eye's optic and focal axes.
• the center of the pupil is not directly measurable from the image sensor, typically a camera (a regular camera or video camera).
• the pupil center is estimated by observing the edges of the pupil and calculating the center location from the edge measurements. Due to the fact that the pupil lies behind the corneal surface of the eye; however, a ray from the center of the physical pupil does not arrive precisely at the center of the pupil image. When the eye is looking away from the camera, the curved cornea refracts the rays from the various pupil edge points differently. Thus, as pupil diameter varies concentrically about its true center, the edges in the pupil image move nonconcentrically around the true pupil center point, even if the true pupil center is stationary.
• the illuminators are placed close to the optical axis of the imaging sensor, which causes the pupil to appear lit up, enhancing the camera's image of the pupil, which is called the bright pupil effect.
• the illuminators can be placed away from the optical axis of the image sensor, causing the pupil to appear darker than the iris, called dark pupil effect (also called dark pupil eye tracking).
• dark pupil effect also called dark pupil eye tracking.
• the identification of pupil center and then the pupil diameter can be obscured by the movement of the head along the camera axis.
• Some remote pupilometers based corneal reflection technologies further include some types of head restraint to prevent head movements to improve the accuracy of the measurement.
• the pupilometer takes account of the head motion by measuring variations in the range between the camera and cornea of the eye, and then it uses the range information to minimize gazepoint or pupil center errors resulting from longitudinal head motions.
• the preferred pupil response measurement system might further include one or more computers, to which the pupilometer is preferably attached through some electronic means, such as electronic wires, optical wires or through wireless transmission.
• the pupilometer's image processing software then can be installed in the computer to process and analyze the pupillary response data.
• the illuminators, infrared LED embedded in the infrared video camera can be placed next to or on the computer monitor in an unobtrusive way, typically below the monitor, to better observe the participant's eye without distracting the participant.
• the system may have a sampling rate of 50 or 60 Hz: If it operates at 60 Hz it may have a camera field rate of 60 Hz or 120 Hz, and then the image processing software can compute the raw data each 60 th or 120 th of a second in synchronization with the field rate of the video camera.
• the first criterion is the accuracy and sensitivity needed to measure and detect the differences between cognitive efforts associated with varying difficulty levels of the stimuli in order to be able to assess the linguistic comprehension level of the patient. It is also important to consider the requirements of the system in relation to the needs of patients being tested. For example, some systems require a fixed head position to separate eye movements from head movements for high spatial accuracy. Such systems would be appropriate for young, neurologically unimpaired adults, who are highly cooperative and would tolerate restraints to restrict head and chin movement and use a bite-bar to help fix the head. These systems, however, may not be tolerated by adults with physical or cognitive impairments, some older adults or very active young children for whom remote pupillary systems may be more appropriate.
• Pupillary response systems that are unobtrusive, such as remote systems, may be preferable in some natural settings, but with less physical control, the clinicians sacrifice spatial measurement accuracy. Since the assessment tasks in the present invention can be executed with little or no movement, if the participants are alert and cooperative, then it may be preferable to explore systems with chin rests or other restraints to limit head movement so long as it does not induce any non-cognitive pupillary response that might mask TERPs. In some cases, the effect of such restraints can be examined in the baseline tasks and then subsequently removed through the subtraction method.
• the different pupillary response systems differ in the amount of time required to position and adjust system-related hardware. For example, if a particular system requires the use of a bite bar, this will add time to the set-up. If portability is required, it is a good idea to consider a system that could be installed on a cart that may be moved to different testing or assessment areas. Some systems operate best under special lighting conditions and the luminance levels must be considered. Typically, incandescent light (generated by standard light bulbs) contains some infrared components and thus is not preferred because it may degrade performance accuracy.
• the pupillary response system used was an LC Technologies Eyegaze system, which is a remote pupil center/corneal reflection system.
• the system entails the use of a near-infrared light shone on one of the participant's eyes. Two points of the light's reflection on the eye, one from the pupil and the other from the cornea, are recorded via an analog video camera (located below the computer monitor in Fig. 2) with a sampling rate of 60 Hz.
• the video signal is then digitized, enabling a vector calculation of the pupil center and pupil diameter relative to the visual display based on the two points of reflection.
• Calibration procedures involve a patient viewing a series of five or more blinking dots on the screen from a distance of 34 inches from the monitor.
• the system can also track eye-fixation and durational data.
• the pupillary response system compensates for minor head movements via the Edge Analysis system, which uses the patented Asymmetric Aperture Method to measure variations in the range between the camera and the cornea of the eye, and then uses the range information to minimize gazepoint tracking errors resulting from longitudinal head motions.
• the next step 15 of the inventive method is dependent upon whether the patient's linguistic comprehension is to be assessed on the basis of verbal comprehension or on the basis of the reading comprehension. If linguistic comprehension is to be assessed on the basis of verbal comprehension, a clinician initiates a first comprehension assessment trial by providing the patient with a pre-recorded verbal stimulus (also called auditory presentation). It is contemplated that various other methods of auditorily presenting the verbal stimulus to the patient can alternatively be used so long as the auditory presentation can be done uniformly and without causing undue excitement in the patient to mask or interfere with the measurements or analysis of task-evoked responses of the pupil (TERPs).
• a pre-recorded verbal stimulus also called auditory presentation
• Pupil dilation can respond more significantly to factors other than cognitive processing, such as light, close-up objects, and emotional factors.
• the list is preferably presented to the patients through an auditory means so as to avoid any visual impact on the pupillary response (also called auditory stimuli).
• Auditory means can be an actual person speaking the word or sentence.
• pre-recorded auditory versions of the verbal stimuli are used. For example, to North American patients, the auditory stimuli are recorded by an adult male native speaker of American English. This avoids the distraction offered by a foreign accent to the North American English speaking patients. Of course, if patients are speakers of British English, the speaker may be British.
• the recording can take place in a sound-proof booth using a high-quality microphone directly connected to a PC. Further, the speaker records each word or sentence multiple times in uninterrupted strings. The token with the best quality in terms of articulation and word-level stress is selected by one or more listeners in some kind of agreement (for example, 100% agreement). Then each verbal stimulus can be further digitized, normalized for intensity, and stored on the computer for repeated usage. The participant can listen to the recording through a speaker or through a headphone.
• the patient is instructed to look at a fixation point (see Fig. 2).
• the fixation point can be a dot or dots, a circle or circles, or a square or squares, any simple figure, letter, shape or drawing that would merely provide a fixation point for the gaze of the patient for the ease of measuring the pupillary responses of the patient during the auditory presentation process (similar to the filler stimulus illustrated in Fig. 7).
• the fixation point should not be any image or figure that would distract the attention of the patient from listening to the auditory presentation of the verbal stimuli.
• the fixation point should be similar in luminance to any other image to be displayed so as to prevent any pupillary change due to change in luminance. More importantly, the fixation point should not elicit any cognitive processing, such as the use of a usual geometric figure or drawing or letter, which would mask pupillary responses related to the processing of the auditory stimuli.
• the patient will be instructed to "Listen to the words and sentences while you look at the dot on the screen. Be sure to listen carefully and pay attention to the meaning of what you hear.”
• the pupil response data are measured and recorded for each verbal stimulus during the presentation of the stimulus, preferably for a period of time ranging from 200 milliseconds to 10 seconds. More preferably, the period of time ranges from 300 milliseconds to 4 seconds. In order to keep the time frame consistent between the tasks or each stimulus presentation, there preferably is a time window in the range of 2 to 4 seconds between the offset of one auditory stimulus and the onset of the next.
• assessment trials are administered in a similar manner to that described above except that textual stimuli versions of the verbal stimuli are presented to the patient in the center of the visual stimuli displays (see Fig. 2) and other considerations described in detail below.
• a patient is simply instructed to read the text displayed in the middle of the screen, and the patient' s pupillary response data are recorded and assessed in the manner described above.
• the textual presentation of the verbal stimuli involves presenting words to a patient visually through a written text. For example, instead of saying "banana” to a patient, the written word “banana” is presented to the patient textually/orthographically.
• the verbal stimuli can be presented to the patient auditorily and textually/orthographically at the same time or sequentially.
• the word "banana” can be spoken to the patient while the text of the word can be presented to the patient simultaneously or immediately thereafter.
• the words can be written on a paper, a board, or be put on a computer screen. Then, the presentation of the word to the patient is preferably controlled so as to minimize the impact of the light and color on close-up objects on the pupillary response of the patient, to avoid confounding the results. Light and color may have significant impact on pupillary responses of a patient.
• the magnitude of pupillary light reflection (pupil diameter may range from one to nine mm) is much larger than the magnitude of TERPs (usually less than 0.5 mm) (Beatty & Lucero-Wagoner 2000), and can thus mask TERPS.
• the magnitude of the pupillary dilations differs for the difficult tasks between light and dark conditions.
• the text of the word is preferably written in black and white.
• the luminance of the computer screen is preferably adjusted to an ambient level.
• the light is preferably controlled by adjusting and/or monitoring ambient room lighting and/or any visual stimulus items with a light meter.
• the accommodation reflex which involves bilateral constriction of the pupils in response to images within 4 to 6 inches of a patient's nose, can be easily controlled by placing any visual stimulus items greater than 6 inches away from the patient's nose.
• the final step 17 of the inventive method is analyzing and interpreting the pupillary response data for all verbal stimuli presented through the above test protocols.
• the pupillary response data relative to the cognitive effort are called "task-evoked responses of the pupil” (TERPs).
• TERPs are defined as "a time-locked averaged record of pupillary dilation and constriction occurring during the performance of a mental task" (Ahern & Beatty, 1981, p. 122). TERPs occur shortly after the onset of processing, typically within 100-200 milliseconds, and then subside quickly following the termination of processing.
• Dilation and constriction of the pupil are controlled through the radial (dilator) and circular (constrictor) muscles of the iris, which are governed by the autonomic nervous system, which regulates cortical arousal.
• These responses are not under volitional control, and thus, the response cannot be controlled or modified by the patient as it can be done by eye-fixation methods. Therefore, the results can be relatively free of confounds associated by the patient's intentional control of the response that is not related to the patient's linguistic comprehension level, to avoid confounding the results of the assessment.
• Kahneman (1973) suggested that pupillometry can be used to assess task difficulty.
• the studies have been done on correlation between pupillometric indices and various cognitive or linguistic tasks according their difficulty levels.
• tasks used are based on memory, such as memory loads for words and digits, and on uncommon linguistic manipulations, such as letter discrimination and cross-linguistic interpretation.
• These tasks are not common or everyday linguistic usage, requiring more intensive cognitive efforts and thus larger pupillary responses, which might not correlate to the difficulty levels associated with regularly used words. For example, unusual words or less frequently used words are considered more difficult, thus requiring more effort to recognize and/or comprehend.
• these relatively large pupillary responses are likely also caused by factors other than linguistic comprehension, such as emotional factors (excitement over the unusual way of using language) or other linguistic skills (short-term memory skills), understanding of the task instruction, and/or level of education needed to understand the linguistic task.
• factors other than linguistic comprehension such as emotional factors (excitement over the unusual way of using language) or other linguistic skills (short-term memory skills), understanding of the task instruction, and/or level of education needed to understand the linguistic task.
• these tasks are not likely to result in pupillary data that can be analyzed to show a patient's actual linguistic comprehension level so as to assess whether the patient has a linguistic impairment or even the impairment level as compared to a person without neurological impairment.
• the effects of other factors such as light, memory, or understanding of instructions, can easily mask the responses from TERPs.
• many variables can reduce the validity and reliability of the responses from task-evoked pupillary responses.
• These responses include both physical variables and psychological ones. Relevant physical variables include, but are not limited to, general peripheral system differences between patients, distance from the object, and the effects of light and brain injury on pupillary responses.
• Relevant psychological variables include, but are not limited to, anxiety, fear, and other emotional response that can contribute to potentially confounding factors. All these variables can be attributed to patient, stimulus, and environmental conditions. More importantly, these factors can affect the pupil dilation, which can impact the accuracy of any pupillometric experiments. It is difficult to control these variables to minimize their impact on the task-evoked pupillary response while preserving and enhancing the sensitivity of the task-evoked pupillary response to relatively small effort exerted in the normal everyday linguistic processing.
• the present invention is able to provide valuable information regarding individual differences in cognitive and linguistic abilities for clinical assessment despite the numerous factors that can influence TERPs values, and can also be used as the basis for the formation of treatment plans for impaired patients.
• the magnitude of pupil dilation as related to cognitive effort is measured in several different ways: by obtaining a simple maximum measure—the single highest amount of dilation observed during a set time period, by calculating a mean or average, pupil dilation over a response interval, and by measuring the latency to peak—the amount of time it takes a participant to reach peak pupil dilation during a task.
• TERPS can be calculated in three different ways in order to compare significant results across computation methods: absolute values, subtracted values, and normalized values.
• Pupillary response data also called "dependent measures” consist of mean pupil diameter, maximum pupil diameter, and latency to maximum pupil diameter for the absolute value, subtracted value, and normalized pupil data.
• Commercial or custom software can be used to extract data related to dependent measures.
• mean and maximum TERPs can be reported as millimeters of pupil diameter, rather than a change in dilation.
• the average pupil diameter obtained during a baseline task will be subtracted from mean and maximum TERPs in order to obtain the amount change, in millimeters, induced by the assessment tasks.
• the baseline task as illustrated by Fig. 3 is often used to obtain the baseline measures of each patient's pupillary responses so that emotional effects can be controlled by subtracting the baseline pupil diameter from the TERPs, resulting in the measurement of relative increase in pupil dilation due to experimental tasks alone. Latency of maximum pupil diameter for both methods will be reported in milliseconds between the initiation of each trial and the single maximum pupil diameter obtained within each trial.
• a grand mean pupil diameter is obtained by averaging all of the pupillary responses from each condition or task or for the entire experiment.
• a condition can be a task associated with a set of easy nouns, or a task associated with a set of difficult nouns.
• To obtain a normalized measurement of a mean pupillary response divide each individual pupillary data point in the analysis time-frame by this grand mean for that condition or task. The normalized data will then be averaged at each time point over all participants to obtain a waveform of pupillary dilation in each condition. Then, normalized data can be submitted to an optional simple regression analysis with time as the independent variable and the normalized pupil data as the dependent variable in order to obtain the slope of pupillary change for each condition.
• the mean pupil dilation measure is dependent on the time frame during which raw data for this measurement is calculated.
• the time frame is restricted to the completion of a certain portion of the task or to a maximum period. For example, the time frame is restricted to three seconds from a predetermined time period.
• the peak pupil dilation measure is more sensitive to noise, but this measure is not affected by the total number of data points in the measurement period. From this measure, latency to peak measure can be calculated based on the amount of time it takes a participant to reach peak pupil dilation. This latency to peak measure allows the clinicians to observe when a participant's cognitive processing is at a peak, which often occurs immediately preceding the completion or resolution of a task.
• Custom computer software runs the experimental protocol described above for the auditory or textual presentation of the verbal stimuli to the patient.
• the software governs the initial calibration of the patient's eye movements and eye configuration.
• Additional custom software is preferably used to analyze raw eye-fixation, pupil center, and pupil diameter measures.
• the raw eye-fixation is x/y coordinates corresponding to where a patient's eye is focused on the computer monitor, and the raw eye-fixation measures can be used to obtain more accurate measures of pupil center and pupil diameter to accommodate for minor head and/or eye movements.
• a baseline test in step 35 is administered prior to and/or immediately after the experimental tasks in steps 37 to 38 (also called “assessment tasks").
• the baseline test is administered 35 immediately prior to the experimental tasks in steps 37 to 38.
• the pupillary response during the baseline task can be measured and recorded 36, and then be used as the baseline value for each individual trial or for analysis of the pupillary values for all stimuli in step 39. While not wishing to be bound by theory, it is presently believed the baseline values can be used to control emotional effects in order to obtain the measurement of relative increase in pupil dilation due to experimental tasks alone.
• pupil dilation also called pupillary response
• Relevant physical variables include, but are not limited to, general peripheral system differences between participants, distance from the object, and the effects of light and brain injuries on pupillary responses.
• Relevant psychological variables include, but are not limited to, anxiety, fear, and other emotional responses that can contribute to potential confounding factors, which can affect the pupil dilation and the accuracy of any pupillary experiments.
• the present inventive method attempts to control several variables so as to increase or heighten the probability that measures designed to measure TERPs provide valid and reliable responses. Emotional factors may be somewhat difficult to control because every individual reacts differently to testing or assessment environments.
• the baseline test is one of the preferred ways to control the emotional effects in order to obtain TERPs due to experimental tasks alone.
• Light is preferably controlled in the present method by using a light meter to monitor ambient room lighting as well as luminance of any visual or textual stimulus items.
• the accommodation reflex which involves bilateral constriction of the pupils in response to images within 4 to 6 inches of a patient's nose, can be easily controlled by placing any visual stimulus item greater than 6 inches away from the patient's nose.
• the visual stimuli are preferably designed so as to minimize the presence of distracting visual features.
• Distracting visual features include color, shading, background, size and luminance.
• the visual stimuli preferably consist of black and white images, in which the shadings are minimized as much as possible without degrading image quality.
• a white background and a standard size are used.
• the visual image can be put on a board, a paper, a computer screen, or other similar device. If the visual image is put on the computer screen, the luminance should be controlled and monitored through a light or luminance meter.
• the baseline measures of pupil diameter of the patient were obtained prior to the initiation of the above tasks.
• the baseline measures are used to control emotional effects on the pupil diameter so that the resulting pupil diameters are analyzed relative to the baseline results either by subtraction or other similar methods.
• TERPs index the change in the pupil diameter induced by the task, not the value of the pupil diameter in absolute terms (although comparisons of pupil diameters in absolute terms can also be used under the assumption that TERPs are stable over baseline values).
• the baseline measurement is preferably obtained when no cognitive processing is taking place.
• a “condition” refers to a specific set of stimuli designed to elicit a certain pupillary response due to a certain level of cognitive effort associated with processing this set of stimuli. For example, a set of easy nouns is a condition, while a set of difficult nouns is another condition. Similarly, a set of easy sentences is a condition; while a set of difficult sentences is another condition.
• Baseline tasks can be simply looking at a blank, lighted display for a period of time prior to experimental or assessment trials.
• the luminance of a blank and lighted screen may be different than the luminance of a computer screen containing images, resulting in possible or potential confusion between light-induced pupillary responses with task- induced pupillary responses.
• the luminance of the blank screen may be higher than the luminance of images that may be presented later in which some portions of the screen are black or shaded. Problems ensuring luminance consistency may be avoided by manipulating all stimuli so that luminance values are similar across all tasks.
• the baseline tasks should contain similar visual stimuli as that of the assessment task.
• the similar visual stimuli can be a similar word, similar sentence, or similar image. Any difference between the baseline task and the assessment task must be monitored or adjusted so that it would not induce any processing that could obscure TERPs.
• the similar visual stimuli can be all crosshairs instead of actual words. This choice might maintain equal luminance while reducing any sort of linguistic processing that might take place while reading a "neutral" or similar sentence or word.
• the visual stimuli used in the baseline task are all of the actual visual stimuli to be used throughout the assessment test.
• the baseline pupillary response will be the amount of pupillary change elicited by the visual stimuli alone without any processing of the word. That is, the patients to be assessed can be presented with all images that are later used in the assessment task or test without any accompanying verbal stimuli, and without providing any instructions other than "Look at the images.” Although it is impossible to control what the patients might be thinking as they are exposed to these images, it is believed that the differences in pupillary dilations during the task might be in relation to luminance alone without any processing elicited by a language task.
• the placement of the baseline task within the overall experiment is also important to consider.
• the pupillary response during the baseline task can be measured before and/or after the assessment task, and then be used as the baseline value for each individual trial. This may be an effective way to ensure that baseline pupil diameter is not affected by any anxiety over the task or by pupillary dilations sometimes elicited by response preparation.
• the baseline measurement can be obtained for each individual trial. This method of baseline measurement has an advantage in that any residual processing related to any specific trial or any anxiety related to the specific trial will be taken into account in the measurement of the TERPs.
• the experimental tasks can further include an optional attention retaining component, such as a comprehension test, as illustrated in Fig. 8. While not wishing to be bound by theory, it is presently believed that a comprehension test can be used to keep the patient' s attention focused on the task during the assessment.
• the comprehension test comprises asking simple comprehension questions by a clinician or an examiner.
• the experimental tasks can include about 10 to 30% of the comprehension questions.
• the patients for the test can be instructed in the beginning that they will be asked to recall as many stimuli as possible, or that they will be required to answer questions regarding the stimuli that were viewed during the test. It is not necessary to actually include these follow-up tasks, or to analyze any results obtained from them if they are included.
• This type of instruction can be used as an alternative to the comprehension test to ensure active listening by patients, and may or may not lead to more sensitive measurement of pupillary movements.
• Other ways of possibly eliciting more active attention would be to add a decision-making task, such as a button-press if the stimuli are matching or nonmatching.
• the presentation of the verbal stimuli can also be accompanied by the presentation of the visual stimuli either simultaneously or immediately thereafter (see Fig. 4).
• the method includes the steps as illustrated in Fig. 4. Referring to the first step 41 of the method for using the combination of visual and verbal stimuli to assess the linguistic comprehension level of the patient as set forth in Fig. 4, each visual stimulus includes at least one image that corresponds to the verbal stimulus being presented at the same time as or immediately prior to the visual stimulus. Preferably only a single image is presented to the patient along with the presentation of a single corresponding verbal stimulus (a word or a sentence) as shown in Fig. 5.
• the verbal stimuli are varied in terms of word difficulty and also whether or not they match the image shown.
• the patient is preferably administered hearing and/or vision screenings 42 followed by positioning the patient in front of a screen 43 and configuring the pupillary response system to measure patient's pupillary responses 44, all which are substantially the same as described in detail in the above section.
• a baseline test 45 is preferably administered to obtain relevant baseline pupillary response data to minimize or eliminate the effect of emotional or other environmental factors on the analysis of TERPs, the process of which is substantially the same as described in detail in the above section.
• next steps 46 to 47 as set forth in Fig. 4, a verbal stimulus from the list of the verbal stimuli is presented to the patient 46 while a corresponding visual stimulus is presented to the patient at the same time or immediately thereafter 47.
• Pupillary responses are measured and/or recorded 48 during the presentation of the visual stimulus.
• the steps 46 to 47 are repeated 48a for each pair of verbal-visual stimuli in the list, and then the pupillary response data are analyzed and interpreted 49 in substantially the same way as described in the above section.
• the patients can be instructed to "listen to the words and look at the pictures on the screen.”
• the word "banana” is spoken to the patients, and at the same time the image corresponding to the word, an image of "banana,” appeared on the screen (see Fig. 3).
• the patients are given a period of time, ranging from about 200 milliseconds to about 10 seconds, to view the image before the computer automatically advances to the next stimulus item.
• the viewing time frame provides the patient with ample time to process the stimulus.
• Task-evoked pupillary responses have been shown to occur within 100-200 milliseconds following the onset of the cognitive processing, and then quickly subside following the termination of the processing.
• Foil Stimuli Trials During the assessment test, the patient's attention may drift away from the task at hand. To keep the patient focused on the task, optional foil trials are inserted into the task as set forth in Fig. 9. The pupillary response data for the foil stimuli can be measured, recorded and analyzed to understand more about the patient's cognitive ability. Further, these data are compared to the pupillary response data for the experimental tasks for more in-depth evaluation of the patient's linguistic comprehension according to different difficulty levels of the stimuli. Foil trials are trials in which the visual and auditory stimuli do not match. For example, in Fig.
• foil stimuli should be similar to the stimuli used in the test in terms of complexity and other factors. For example, for single word stimuli tests, the same verbal stimuli and visual stimuli are used but are paired differently so that the visual stimuli do not match the verbal stimuli.
• 10 to 30% of the assessment test should consist of the foil trials; more preferably, 20% of the test consists of the foil trials.
• filler Stimuli can be interspersed in the assessment test in order to prevent pupillary changes due to an abrupt change in luminance between trials as shown in Figs. 10 and 11.
• Filler stimuli and the foil stimuli can both be included in an assessment test as shown by Fig. 11.
• the preferred filler image can include one or more dots, one or more circles, one or more squares, one or more simple letters (such as "X"), or other similar shapes/letters/drawings/figures. It is important to note that the filler image should be similar in luminance to any other images shown to prevent pupillary changes due to change in luminance.
• the filler image should not elicit any cognitive processing, such as the use of a usual geometric figure or drawing or letter, which would mask pupillary response related to the processing of the auditory stimuli.
• 10 to 30% of the test preferably consists of the filler image.
• verbal stimuli can be words or sentences.
• Verbal stimuli can be presented to patients audibly or textually by themselves; or alternatively, the verbal stimuli can be presented with the corresponding visual stimuli to the patient.
• the verbal stimuli are separated into two or more sets of verbal stimuli with substantially different difficulty levels.
• there are two sets of verbal stimuli with substantially different difficulty levels such as one set being substantially easy while the other set is substantially difficult.
• Stimuli that have a clear delineation between "easy” and "difficult” can be used reliably to assess the degree of correlation with TERPs. More importantly, this behavior measure may lessen the potential influence of many confounds associated with people with neurological impairments, such as speaking or limb-motor deficits.
• the selection of the words as the verbal stimuli of the present invention according to these differing levels of difficulty are based on several criteria: age of acquisition, word frequency, familiarity, naming latency, length of the word, pronunciation, other similar factors or criteria, or combinations thereof.
• Some stimulus words may be selected from the Snodgrass and Vanderwart (1980) word set.
• Corresponding visual stimuli may be found in the Rossion and Pourtois (2004) image set. These images, based on images from the original Snodgrass and Vanderwart (1980) image set, may be preferred because computerized images are available, which allow for manipulation of the images to reduce differences in luminance.
• the words are selected according to the estimated difficulty so that each word fits clearly into one of two categories: easy or difficult.
• Combinations of four types of measurements (criteria) are preferably used to approximate word difficulty: age-of-acquisition estimates, word frequency measurements, word familiarity estimates, and naming latency measurements.
• Word frequency has been shown to correlate highly with the difficulty level of a word.
• the assumption with regard to word frequency as it relates to the difficulty of a word is that difficult words are likely to appear less often, and words that are more commonly encountered will be learned faster and remembered better. Breland (1996) found that the correlations between the word difficulty estimates and the word frequency indices are high.
• Word frequency measurement for the present invention can be taken from the Kucera and Francis frequency norms ((Kucera & Francis, 1967). Reliable references can also be used to provide the word frequency measurement for estimate of the word difficulty in the present invention.
• words that are classified as “easy” or “difficult” according to at least two out of the four categories are considered for final selection as “easy” or “difficult” words.
• the results from Example 1 show that this method of categorizing nouns as easy and difficult was reflected in TERPs.
• a composite estimate of word difficulty based on all four measures can be used, in which more weight is given to the age-of-acquisition measure.
• Example 1 also shows that age of acquisition appeared to be the most important indicator of word difficulty: age-of- acquisition was positively correlated with mean pupil diameter in both control patients and the patients with aphasia (PWAs).
• Easy and difficult word lists then are preferably balanced to include equal number of words consisting of one-, two-, and three-syllables in order to reduce the impact of word length to focus on the pupillary response to the difficulty level based on four measures only.
• Easy and difficult sentences can be based on active and passive sentences, sentence length, sentence branches, number of verbs in a sentence, and imbedded clauses, respectively.
• easy and difficult sentences may be based on active and passive sentences: an easy sentence can be an active sentence, while a difficult sentence can be a passive sentence.
• Sentences can be syntactically and semantically reversible so that if the subject-verb-object is ordered in one way, the sentence can be an active sentence; while if the subject-verb-object is ordered in another way, the same sentence can be changed into a passive sentence. This way, any potential confounds associated with different sentence content are reduced or eliminated, focusing the pupillary response on the difficulty level of the sentence as related to its active/passive structure.
• VAST Verb and Sentence Test
• EPTAC Eyetracking Picture Test of Auditory Comprehension
• the key difference between active and passive sentences is the ordering of the constituents within the sentence.
• Active sentences similar to many English sentences, are composed with the subject of the sentence appearing first, followed by the verb, then finally by the object of the verb.
• the subject-verb-object (S-V-O) ordering of thematic constituents within a sentence is termed the canonical, or standard, ordering of constituents in the English language. With this ordering, the subject of the sentence is typically assigned the thematic role of an agent, or the doer of the action. The object of the sentence, therefore, is typically assigned thematic role of the theme, or the person/thing that is undergoing the action.
• Color functions as a distractor in image-based tasks. Colored items attract more immediate and longer attention when presented along with black and white items, or items that significantly differ in color. Deffner (1995) conducted a study of image characteristics considered critical in image evaluation. Participants were shown a series of images and were instructed to express their preferences regarding image quality. Color saturation, color brightness, and color fidelity were all items shown to influence how participants viewed images.
• Size When viewing multiple images within one display, relative size is a physical property of images that influences scanning patterns.
• the size of a stimulus refers to the spatial extent of the item. The disproportionate size of an object is likely to attract disproportionate attention to images within a multiple choice display. The viewer is more likely to focus on the biggest or the smallest object in a display of several images.
• Depth cues Shading, highlight details, and shadow contrast have been shown to influence eye movement patterns when viewing images. Individuals allocate more attention or pupillary response to visual stimuli cued in depth through shadows, for instance, than to two-dimensional stimuli without depth cues. Disproportionate looking at a multiple-choice image display occurs when two dimensional images and images with depth cues are displayed together.
• Luminance Barbur, Forsyth, and Wooding (1980) found that background color and luminance have an impact on viewers' visual scanning patterns. In their study numbers were recalled better using a middle-grey background instead of a black one. The correct performance of tasks also increased when the luminance of the background was greater than one-third of that of the target. Additionally, contrasts in luminance have been demonstrated to be recognized faster and also with higher frequency than changes in motion and complexity. Different degrees of luminance of images may cause a disproportionate pupillary response in multiple-choice displays. Likewise, luminance differences between the backgrounds of the images can influence the viewer's visual attention as well.
• Clarity The time a viewer spends fixating on images tends to be greater when the image is blurred than when it has clear boundaries. If images in a multiple- choice display have different grades of clarity, the viewer is likely to have a larger pupil dilation on the most blurred image such that the pupil response would not be balanced among images within the list, resulting in pupillary responses due to non-cognitive factors that would mask the analysis of TERPs.
• Scene context The background or context has an impact on accuracy of identification of objects. If participants are shown images with targets in a typical context, then it is easier to identify them, compared to when they are presented without context. Disproportionate looking may be evoked when the context of images within a display is not controlled. For example, if some objects in the visual stimuli list are shown in isolation while others are shown within a scene context, the distribution of pupillary response is not likely to be balanced among the isolated objects and the images with scene contexts. Likewise, if one object is displayed in an unusual or inappropriate context, the viewer might need more time to identify the object accurately and a disproportionate effect on the pupillary responses might occur as well.
• Imageability refers to the ease and accuracy by which a semantic idea is conveyed by a visual stimulus. It corresponds to the notion of abstractness versus concreteness of a depicted concept. If one or more of the target images within a display are not “imageable", this may influence where a person looks within a display. For example, it is harder to represent the abstract concept of "angry” than to represent the concept “flower” or “ball”; the image for "angry” may disproportionately attract a viewer's attention when shown along with images of a flower and a ball.
• the imageability of concepts is said to underlie the finding that objects are recognized faster and at higher rates than actions when controlling for physical stimulus features. The authors' interpretation for these results is that stationary objects, such as a chair or lamp, are easier to distinguish from one another, whereas actions look similar. This factor can be used to distinguish the difficulty levels of the words and/or sentences.
• Concept frequency is a construct representing the frequency with which an individual encounters a particular concept in everyday life. The construct parallels in the cognitive domain what word frequency represents in the linguistic domain. The ease or difficulty in processing a word is reflected in the pupillary response on this word while reading. The pupillary response depends not only on the number of syllables in a word but also on the word's predictability. Compared to high- frequency words, low-frequency words tend to elicit a higher pupillary response— larger pupil diameter.
• word frequency and concept frequency are not identical, objects representing concepts that correspond to low and high-frequency words shown together within a display are likely to cause disproportional pupillary responses.
• the purposes of this example were (1) to develop and test a method for indexing pupillometric responses to differences in word difficulty for participants with and without aphasia; (2) determine whether or not the degree of effort that participants with aphasia exhibit for easy versus difficult words is associated with the severity of their comprehension deficits and/or overall aphasia.
• To examine differences during the processing of easy versus difficult words two groups of participants were tested: a control group of adults without neurological impairments, and a group of PWA. The following research questions were addressed:
• Pics Logarithmic Visual Acuity Chart (Precision Vision, 2003) with or without the use of glasses or contact lenses. All control participants passed the visual screening; one PWA failed. Participants were not excluded based on the results of the vision screenings; however, any deviance from normal was documented. Visual fields were examined by having each participant identify the number of fingers being held in each of the four quadrants of the visual field while maintaining gaze on the examiner's face. Three control participants missed the top right quadrant; one PWA missed the top right quadrant; two PWAs missed the lower right quadrant; three PWAs had a right field cut; and one PWA has a left field cut.
• MMSE Mini-Mental Status Examination
• Inclusion criteria specific to PWA included three factors: (1) diagnosis of aphasia due to stroke based on a referral from a neurologist or a speech-language pathologist, which was confirmed via neuroimaging data; (2) no reported history of speech, language, or cognitive impairment prior to aphasia onset; and (3) post-onset time of at least 2 months to ensure reliability of testing results through traditional and experimental means. Only participants who had aphasia following a cortical stroke were recruited. Any subcortical lesions were recorded.
• PWAs were also administered the Aphasia Quotient (AQ) components of the Western Aphasia Battery-Revised (WAB-R, Kertesz, 2007).
• the AQ portion of the WAB-R consists of the following subtests: Spontaneous Speech, Yes/No Questions, Auditory Words Recognition, Sequential Commands, Repetition, Object Naming, Word Fluency, Sentence Completion, and Responsive Speech.
• the results from this AQ portion of the WAB-R, along with that of the Auditory Verbal Comprehension portion (which consists of the Yes/NO Questions, Auditory Word Recognition, and Sequential Commands subtests) were used for the analysis of the results for PWAs.
• PWAs were classified as mild (AQ ranged from 76 to 100), ten PWAs were classified as moderate (AQ ranged from 50 to 75), and five PWAs as severe (AQ ranged from 26 to 50). Twenty-one PWAs were classified as having anomic aphasia, five PWAs as having conduction aphasia, and nine PWAs as having Broca's aphasia. One PWA was classified as having either Broca's aphasia or transcortical motor aphasia, and two PWAs were classified as having conduction or anomic aphasia.
• a Maico MA25 Audiometer (Maico Diagnostics) was used to screen participants' hearing. Boston Media Theater speakers (Boston Acoustics, Inc.) were used to present auditory stimuli and sound-field hearing screening stimuli.
• An Eyefollower 2.0 Eyegaze System (LC Technologies) was used to monitor participants' eyes and to measure and record pupillary movements. The Eyefollower 2.0 Eyegaze system measured participants' gaze points at a rate of 120 Hz, and generated pupil diameter for each camera image sample for both eyes (LC Technologies, Inc., 1009). Custom software was used to derive all pupillometric measures from the raw data collected.
• Luminance of all visual stimuli was measured using a Gossen Starlite 2 light meter.
• Stimulus words were selected from the Snodgrass and Vanderwart
• Snodgrass and Vanderwart (1980) found that Carroll & White's (1973a) age of acquisition estimates correlated highly with rated familiarity for the 87 images in their experiments.
• the current study used the 1996 estimate of Snodgrass and Yuditsky for age of acquisition for 250 images in the Snodgrass and Vanderwart (1980) word set.
• Word frequency has been shown to correlate highly with word difficulty.
• Snodgrass and Vanderwart' s study they instructed participants to give familiarity ratings to 260 picture stimuli, the familiarity rating being "the degree to which you come in contact with or think about the concept" (p. 183). Participants were asked to rate the images on a 5-point scale, with a rating of 1 indicating very unfamiliar and 5 indicating very familiar. Results suggested that the familiarity rating was positively correlated with frequency and negatively correlated with age-of-acquisition ratings. Therefore, words that are more familiar typically occur more frequently and are learned at an earlier age.
• Words that were greater than one standard deviation above the mean for familiarity rating were considered “easy”; words that were greater than one standard deviation below the mean were considered “difficult.”
• Words that were greater than one standard deviation above the mean for frequency estimate were considered “easy”; words that had a frequency rating of zero or one were considered “difficult.”
• For the category of frequency estimate due to the rating value and the relationship between the mean and standard deviation of the sample, it is not possible to obtain words one full standard deviation below the mean.
• Words that were greater than one standard deviation above the mean for age-of-acquisition estimates were considered “difficult”; words that were greater than one standard deviation below the mean were considered “easy.”
• Words that were greater than one standard deviation above the mean for naming latencies were considered “difficult”; words that were greater than one standard deviation below the mean were considered “easy.”
• Color images from Rossion and Pourtois (2004) were chosen to match selected words.
• color images were individually converted to black-and-white images using Adobe Photoshop CS3 Extended ® (2007). Specifically, each image was imported into Photoshop, and then converted into monochrome using the channel mixer: Individual source channels (red, green, and blue) were altered to produce an image that was as close as possible to a line drawing, for example, shadings were minimized as much as possible without degrading image quality.
• the PIC images generated in the first step were imported and layered onto a standard sized, white background, and then saved as JPEG images. This step was done to prevent image distortion once the images were displayed during the study.
• Luminance a measure of light emitted from a source, of all images was measured using the Gossen Starlight 2 light meter in order to account for possible effects of light on pupil diameter.
• Sixty-six percent (24/36) of the images' luminance was within one standard deviation of the mean.
• One image's luminance was greater than two standard deviations below the mean.
• the six foil words corresponding to auditory stimuli were arranged alphabetically and each assigned a number from 1 to 6.
• a random number table was used to assign the numbers 1 to 6 to the visual stimuli.
• the word “artichoke” was assigned the number 1 for the auditory stimuli.
• the first number in the random number table was the number 4, which corresponded to the word "artichoke” in the original list. Therefore, the auditory stimulus "artichoke” was paired with the image "leaf for that particular foil trial.
• Each participant underwent the baseline condition and then the experimental condition. Participants were allowed to take breaks between tasks as needed. Participants sat in a comfortable, high-backed chair and were offered the use of a chin rest in order to aid in head stabilization. Thirty-one control participants chose to use the chin rest; nine control participants did not. No PWA chose to use the chin rest. Each participant was positioned so that his/her head was 24-26 inches from the computer screen during each task in order to prevent the accommodation reflex, which might result in bilateral constriction of the pupils in response to images within 4 to 6 inches of an participant's nose.
• Baseline Condition Baseline measures of pupil diameter were obtained prior to the initiation of experimental trials. During this condition, the participants were exposed to all visual stimuli (both experimental and foil) used in the rest of the experimental condition without any accompanying verbal stimuli. A random order of presentation of experimental and foil stimuli was determined using a random number table (www.siaiirek.com).
• Fig. 5 shows a sample experimental stimulus— an image of a banana; and this image was presented on the computer screen simultaneously with the auditory pronunciations of the word "banana.”
• Fig. 2 shows a sample foil stimulus— image of an artichoke; and this image was presented simultaneously with the auditory pronunciation of the word “artichoke.”
• Fig. 3 shows filler stimulus; the image was displayed for three seconds between each experimental stimulus item.
• each participant was asked to perform a sorting task.
• the participants were given a stack of cards, each of which included an image on one side and the corresponding printed word for each verbal stimulus used in the experiment on the other side.
• the participants were asked to sort each card into one of two piles, easy or difficult. No definition of "difficult” was provided so that each participant could form his or her own operational definition. However, some participants required some instruction on the distinction between "easy” versus "difficult” because the words in the list were relatively easy for these participants.
• Sorting tasks were intended to validate the stimulus selection method as well as to provide individual bases for comparing pupillometric results to perceived word difficulty.
• One type of dependent measures is the method of measuring or evaluating the pupil dilation as related to cognitive processing.
• the magnitude of pupil dilation is linked to intensity and effort involved in cognitive processing.
• the simple maximum pupil diameter could be correlated to the time period immediately prior to a participant's response to a task.
• the other dependent measures are presence or absence of aphasia, the severity of aphasia, and the difficulty level of the stimulus items. These measures may influence (a) the intensity of processing required to complete a task, which may be reflected in the magnitude of pupil dilation; and/or (b) the time frame required to complete the task, which may be reflected in the latency of the simple maximum pupil diameter. If these pupillometric measurements can reliably differentiate between any of the above conditions (i.e., PWA versus controls, mild versus severe aphasia, easy versus difficult words), they can be used in future comprehension testing protocols that do not require overt verbal or physical responses from the participants.
• Table 1 shows three calculation methods of pupil diameters, using the onset of the visual stimulus as the starting point for the measurement. Table 1
• Latency of maximum pupil diameter (in Subtracting the number of milliseconds msecs) following the onset of the visual stimulus
• Tables 2 and 3 display descriptive statistics and ANOVA results respectively.
• Max maximum pupil diameter
• Latency latency of maximum pupil diameter
• Latency Group 1 66 0.006
• _Max maximum pupil diameter
• Latency latency of maximum pupil diameter
• a Pearson product-moment correlation coefficient (shown in Table 4) was computed to assess the relationship among severity of aphasia (as determined by WAB-R aphasia Quotient (AQ) scores), severity of comprehension deficit (as indexed by WAB-R Auditory Comprehension (AC) scores), and individual responses.
• the coefficient data are summarized in Table 4.
• WAB AQ Aphasia Quotient from the Western Aphasia Battery - Revised
• WAB AC Auditory Verbal Comprehension sections of the Western Aphasia Battery - Revised
• Max - easy maximum measure for easy words
• Max - hard maximum measure for hard words
• Mean - Easy mean pupil diameter for easy words
• Mean- Hard mean pupil diameter for hard words
• Latency - Easy latency of maximum diameter for easy words
• Latency - Hard latency of maximum diameter for hard words.
• Bonferroni correction was not utilized for analysis of this hypothesis and that of the following hypothesis. The use of the correction might have rendered these results insignificant. The correction was not used in order to increase the likelihood of detecting any potential significance, which could possibly guide the future directions of this method.
• age acquisition is a chief determinant in naming latency, and the age of acquisition was shown to be negatively correlated with word familiarity in other studies. In other words, as the age of acquisition increases for a word, the naming latency increases and the word is judged to be less familiar, indicating that a greater amount of effort is required for the processing of the word. Interestingly, there is no significant correlation between pupil responses and the naming latency for the control participants.
• the purpose of this study was to develop and test a novel method for assessment of single- word auditory comprehension abilities in participants with neurological disorders.
• the results of this study indicate that the present invention is able to use pupillometry to capture effects of word difficulty in participants with and without neurological impairments.
• the effect of difficult words was illustrated by using single nouns, all of which many participants believed to be "easy,” suggesting that the method of the present invention may be sensitive enough to capture even subtle differences in the efforts required to process generally easy stimuli.
• the results of the present method not only reveal differences as related to word difficulty, but also differences in the time frame required for the processing of stimuli for PWAs with varying levels of comprehension deficits.
• Tasks in this study can be modified to increase the sensitivity and validity of the pupillometry method of the present invention for assessing the language comprehension for participants with neurological impairments or disorders.
• the complexity of the visual stimuli can be reduced, or the visual stimuli may potentially be eliminated totally, which may result in increased sensitivity to TERPs.
• Studies that have reported significant findings regarding pupillometry have made use of nonvisual tasks, with or without fixation points.
• Studies that did use visual stimuli used images far less complex than the ones in the current study, such as single letters and simple geometric shapes.
• the magnitude of pupillary response is more sensitive to tasks that employ only auditory, rather than visual, stimuli.
• Another aspect that can be improved is the determination of the difficult level of any particular word by using other criteria such as word length and/or pronunciation. Further, pupillary measures can be analyzed to evaluate the differences in difficulty related to sentence repetition, sentence comprehension, sentence complexity, syntactic ambiguity, and prosody.
• the analysis of the pupillary response data can also be modified by using additional or different methods of analysis.
• the pupillary response data for experimental tasks can be analyzed alone without incorporating baseline measures or values.
• pupillary response data for the experimental tasks were compared to the baseline pupil measures obtained during the baseline task (visual stimuli only).
• baseline measure may obscure potential significant results, and may not be necessary in some cases.
• pupillometric method of the present invention can index cognitive intensity/effort involved in the processing of easy and difficult single nouns
• pupillometric method of the present invention can be used to evaluate the linguistic comprehension levels of individuals with neurological impairments, especially with regard to whether or not the individuals have any linguistic deficit.
• the purpose of this example is to test procedural variations of pupillometric methods with individuals without aphasia to validate and standardize the method so that the present inventive method can reliably index cognitive effort and intensity required for processing easy and difficult verbal stimuli.
• Methodological aspects of the previous example, including TERP measurement and modality of stimulus presentation, will be systematically tested.
• the resulting method can be used for the study of effort in linguistic processing in individuals with aphasia or other neurological impairments.
• a total of 40 participants will be recruited form the Athens, Ohio community via flyers, mail, web-based announcements, and word-of-mouth. Participants who complete the study will be paid $10 in cash.
• Inclusion criteria will include: age of at least 21 years; American English as a native language; no history of learning/developmental disorders; no history of traumatic brain injury; no reported history of speech; language or cognitive impairment; no knowledge of the purpose of this study; passing a hearing screening at 500-, 1000-, and 2000-Hz pure tones at 25 dB HL via headphones, and passing visual acuity screening similar to the one conducted in Example 1.
• Exclusion criteria will be bilingualism. Participants will be considered bilingual if a language other than American English is used for conversational purposes for duration of 2 hours per day or longer.
• Visual acuity for near vision will be assessed using the 20/250 line of the Patti Pics Logorithmic Visual Acuity Chart (Precision Vision, 2003) with or without the use of glasses or contacts. Visual fields will also be examined by having participants identify the number of fingers held up in each of the four visual quadrants. Pupillary screening will be conducted for informational purposes only, which include examining pupil size and reactivity to light.
• a Maico MA25 audiometer (Maico Diagnostics) will be used to screen participants' hearing.
• Boston Media Theater speaker (Boston Acoustics, Inc.) will be used to present auditory stimuli and sound-field hearing screening stimuli.
• the EyefoUower 2.0 Eyegaze System (LC Technologies) will be used to monitor participants' eyes and to record pupillary responses/movements.
• the EyefoUower 2.0 Eyegaze system measure participants' gaze points at a rate of 120 Hz; pupil diameters will be calculated for each camera image sample for both eyes (LC Technologies, Inc., 2009).
• Custom software will be used to obtain and analyze all pupillary response data (also called dependent measures), such as maximum pupil diameter, average pupil diameter, and latency to maximum for each condition.
• a condition refers to each type of stimuli, such as easy words, difficult words etc.
• auditory stimuli All verbal stimuli will be classified as either "easy” or “difficult,” and they will be presented to the participants in an auditory manner ("auditory stimuli"). Auditory stimuli will consist of easy nouns, difficult nouns, easy sentences, and difficult sentences. All sentences will be syntactically and semantically reversible. In determining the difficulty levels of the auditory stimuli, linguistic concepts with a clear and robust delineation between easy and difficulty will be chosen.
• Single nouns used in the auditory-visual task of the present example are taken from the list developed in Example 1.
• Single nouns to be used in the auditory-only task will be selected using the MRC Psycholinguistic Database (2012).
• the selection criteria for new nouns are substantially the same as that of Example 1: the values of the following parameter will fall more than one standard deviation of the values of the nouns for each of these factors: frequency, familiarity, age of acquisition, and imagery.
• Easy and difficult sentences will consist of active and passive sentences respectively. All sentences will be syntactically and semantically reversible. The full passive form, including the use of "was” and "by,” will be used for all passive sentences in this study. Active sentences will be considered to be difficult sentences, while the passive sentences will be considered easy sentences. Easy and difficult sentence list will then be balanced for frequency, familiarity, and length in terms of number of words.
• VAST Verb and Sentence Test
• EPTAC Eyetracking Picture Test of Auditory Comprehension
• the key difference between active and passive sentences is the ordering of the constituents within the sentence.
• Active sentences similar to many English sentences, are composed with the subject of the sentence appearing first, followed by the verb, then finally by the object of the verb.
• the subject-verb-object (S-V-O) ordering of the thematic constituents within a sentence is termed the canonical or standard ordering of the constituents in the English language.
• passive sentences are composed with the object of the sentence appearing first, followed by the verb, then finally by the subject (O-V-S).
• the object-verb-subject (O-V-S) ordering is termed the non-canonical ordering of constituents in the English language.
• sentences with non-canonical ordering are more difficult to comprehend than that of the sentences with the canonical ordering (active sentences).
• Auditory stimuli for single nouns for verbal-visual tasks will be taken from the list developed in Example 1. Briefly, additional auditory stimuli for the auditory-only tasks were developed in substantially the same way as that of Example 1. Tokens were recorded by an adult male native speaker of American English in a sound-treated booth using a microphone connected to a PC. The speaker recorded each token multiple times. The token with the highest quality of articulation and word-level stress were chosen by three listeners in 100% agreement. Each token was digitized (22 kHz, low-pass filtered at 10.5 kHz), normalized for intensity to zero dB, and stored on the computer using Adobe Audition 2.0 ® (2006). Auditory stimuli for active and passive sentences will be recorded, selected, digitized, normalized, and stored using the process described above and in Example 1 for single nouns.
• Auditory-only and auditory-visual experimental condition will be counterbalanced between participants. Counterbalancing means that the two conditions were assigned randomly to participants for equal representation between two sub-groups. Items within these conditions will also be counterbalanced; no participant will hear the same sentence in both the auditory-visual and the auditory-only condition. Breaks will be offered between tasks as needed.
• subtest 44 Spoken Word- Picture Matching
• subtest 55 Sentence-Picture Matching, Auditory Version, which will be used to validate intact comprehension and correlate with pupillary results.
• a baseline measurement of participants' pupil diameter will be obtained to allow computation of TERPs via the subtraction method.
• the baseline test will be conducted in the following manner: In between each image in the auditory-visual condition, and presentation of each auditory stimulus in the auditory-only condition, a fixation point will be displayed for three seconds. During the last 500 milliseconds of this period (to allow for any changes in the pupil in reaction to the change of stimuli on the screen), measurements of the participants' pupil diameter will be collected and averaged. This value will serve as the baseline value or measurement for each condition, and will be used during the subtraction method to obtain mean and maximum TERPs.
• auditory-visual task a version of verbal-visual task
• auditory stimuli will be presented simultaneously. Auditory stimuli will be presented via headphones at approximately 65 dB, as determined by a sound level meter. Participants will be instructed to "Listen to the words and sentences and look at the images in any way that comes naturally to you.” Images will be displayed for three seconds following the offset of the verbal stimulus. This time frame for single nouns was used in Example 1, and it is believed that this time frame allows for ample time to observe TERPs. As TERPs typically occur within 100-200 msec following the onset of processing and subside quickly following the termination of processing (Beatty, 1982), TERPs of interest may occur while the auditory stimulus is playing for sentences. Still, visual stimulus items will be kept on the screen for three seconds following the offset of each verbal stimulus in order to allow ample time for participants to process sentences.
• auditory stimuli will be presented via headphones at 65dB. Participants will be instructed to stare at a fixation point on the computer screen, which will be similar in luminance to items presented during the auditory-visual task and the baseline task. This will be done to allow for comparison between auditory-visual and auditory-only tasks. Participants will be instructed to "Listen to the words and sentences while you look at the dot on the screen. You will be asked some questions during the task, so be sure to listen carefully.” In order to keep the time frame consistent between the auditory-visual and auditory-only tasks, there will be a three-second time window between the offset of one auditory stimulus and the onset of the next.
• PALPA spoken word-picture matching and sentence-picture matching subtests of the PALPA (Kay, Lesser, & Colt heart, 1992).
• the PALPA is a widely used test of language abilities in individuals with aphasia. It is also ideal in that control participants do not always score at ceiling levels.
• the results from the PALPA will be used to determine the level at which participants comprehend single nouns and sentences similar to those used during the pupillary assessment portion of the experiment, These results will be correlated with the results obtained from pupillometric measures.
• TERPs will be calculated in three different ways in order to compare significant results across computation methods: absolute values, subtracted values, and normalized values.
• Dependent measures (pupillary response data) will consist of mean pupil diameter, maximum pupil diameter, and latency to maximum pupil diameter for the absolute value and subtraction methods, as described in Example 1, and normalized pupil data for the normalization method.
• Custom software will be used to extract and analyze data related to dependent measures.
• mean and maximum TERPs will be reported as millimeters of pupil diameters, rather than a change in dilation.
• the average pupil diameter obtained during the baseline task will be subtracted from mean and maximum TERPs in order to obtain the amount of change, in millimeters, induced by the experimental tasks. Latency of maximum pupil diameter for both methods will be reported in milliseconds between the initiation of each trial and the single maximum pupil diameter obtained within each trial.
• the normalization method will be similar to the one detailed by Engelhardt and colleagues (2009) and Gutierrez and Shapiro (2011).
• Mean pupil diameter will be obtained for each participant in each condition (i.e., easy nouns, difficult nouns, easy sentences, difficult sentences).
• Each pupillary data point in the analysis time-frame (verbal stimulus item plus three seconds) will then be divided by the mean pupil diameter for that condition.
• the normalized data will then be averaged at each time point over all participants to obtain a waveform of pupil dilation in each condition. Normalized data will also be submitted into a simple regression analysis with time as the independent variable and normalized pupil data as the dependent variable in order to obtain the slope of pupillary change for each condition.
• TERPs i.e., mean (measured in mm), maximum (measured in mm), and latency to maximum (measured in msec)) corresponding to easy and difficulty stimuli.
• Participants will exhibit differences in normalized pupillary responses (i.e., normalized pupillary waveform and slope of pupillary change) corresponding to easy and difficult stimuli.
• Participants will exhibit differences in absolute pupil diameter (measured in mm) corresponding to stimuli presented in the auditory- visual condition and stimuli presented in the auditory-only condition.
• TERPs i.e., mean (measured in mm), maximum (measured in mm), and latency to maximum (measured in msec)) corresponding to stimuli presented in the auditory- visual condition and stimuli presented in the auditory-only condition.
• Participants will exhibit differences in normalized pupillary responses (i.e., normalized pupillary waveform and slope of pupillary change) corresponding to stimuli presented in the auditory-visual condition and stimuli presented in the auditory-only condition.
• normalized pupillary responses i.e., normalized pupillary waveform and slope of pupillary change
• Hypotheses #1 and Hypothesis #2 will be statistically analyzed using a repeated-measures analysis of variance. Any significant main effects will be analyzed using dependent- measures t- tests of means. Analyses will be performed separately for each calculation method (i.e., three different repeated-measures analysis of variance will be conducted, one for the absolute value method, one for the subtraction method, and one for the normalization method).

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