SYSTEM AND METHOD FOR DETECTING DECEPTION
Cross-Reference to Related Applications
The benefit is claimed of U.S. Provisional Patent Application Serial No. 60/341,297 filed December 13, 2001 entitled "System and Method of Detecting Deception by fMRI," U.S. Provisional Patent Application No. 60/396,054 filed 15 July 2002 entitled "Functional Magnetic Resonance Imaging Guided Transcranial Magnetic Stimulation Deception Inhibitors," and U.S. Provisional Patent Application Serial No. 60/341137 filed December 13, 2001 entitled "fMRI-Compatible Skin Conductance Response (SCR) Monitor," which applications are incorporated herein in their entirety by this reference.
Background Deception, as defined herein, is the purposeful misleading of another. There are many military, legal, political, and industrial settings where society could benefit from an accurate method for detecting deception. A variety of technologies and approaches have been developed in the area of deception detection.
Presently, there are a number of lie-detection testing techniques that use polygraph devices. All of the devices examine the peripheral autonomic response to relevant versus irrelevant questions. For example, present day polygraph devices record electro-dermal skin conductance in addition to changes in blood pressure, respiration and peripheral vasomotor activity. Whenever a greater autonomic response to the relevant questions versus the irrelevant or control questions is recorded, this data is interpreted as an attempt to deceive by the individual that is being tested. Polygraph devices have several significant limitations, including the ability of test subjects to develop countermeasures to the techniques that are utilized to detect deception. An additional problem with polygraph devices is that they do not posses the capability to test for a subject's deception but rather measure non-specific peripheral changes in the arousal of the test subject. The substantive predictive value of the polygraph has been found to be poor in many screening and investigative situations, and scientific evidence regarding the polygraph's validity is significantly
lacking. Despite these and other shortcomings, the polygraph continues to be widely used.
Various other techniques have been investigated to predict deception. These techniques include measuring papillary size response to visual stimuli that are mock crime scene related, using voice analysis, facial and hand movement cues to identify subjects who are lying or being truthful, observing verbal cues to detect a true life tale versus a fabricated one, attempting to detect deception in and out of hypnosis, and using high-definition thermal imaging techniques to detect periorbital changes in people trying to deceive. One of the few methods to measure actual brain activity to detect deception involves examining the amplitude of the P300 component of event- related brain potentials. However, this technique has limited utility since it is only applicable when attempting to detect guilty knowledge.
Presently, there is a deficiency of knowledge in regard to the neurobiological or brain basis of the polygraph. Researchers, using functional magnetic resonance imaging and Positron Emission Tomography (PET) have successfully delineated the brain changes involved in response inhibition (e.g., Go/No-Go tasks), divided attention, anxiety, emotion-related learning with reward and punishment, and differentiating components of cognitive breakthrough.
Summary This invention relates to a system and method for detecting deception in a human subject by using functional imaging of the subject's brain alone or in combination with the measurement of skin conductance response of the subject.
This invention allows for the detection of deception in a human subject by using a functional brain mapping techniques such as blood oxygen level dependent functional magnetic resonance imaging (BOLD fMRI), and also in certain embodiments combining the results of the BOLD fMRI with other measures of human psycho-physiologic function including skin conductance response.
BOLD fMRI utilizes the fact that hemoglobin gives off a different magnetic signal when it is carrying oxygen (oxyhemoglobin) compared to when it is not carrying oxygen (deoxyhemoglobin). Thus, brain areas with high demand or that are more active will have a different ratio of oxy-to deoxy-hemoglobin.
By taking very fast images (on the order of an image or more per second) one can rapidly image the contrast between activity at rest and during a specific behavior, thus demonstrating the function of a particular area of the subject's brain as well as its structure. A major benefit of using magnetic based technologies to image as opposed to radioactive based is that there is no limit to the number of scans that can be performed.
The present invention uses BOLD fMRI as one preferred technique to identify unique brain regions of a human subject that are activated during periods of deception or truthfulness. By following a method of posing questions to the subject with known answer categories (i.e. deception or truth), a person skilled in the art of reading BOLD fMRI images can identify the respective regions of the subjects brain that are activated during truth and during deception. Comparing the regions of the brain that are activated during truthful response with the regions activated during deceptive responses can help to determine what regions of the brain are active during truth and during deception.
Traditional indications of deception such as skin conductance measures can be used to provide additional indications of deception. Further, by coupling the results of the BOLD fMRI images with measures of psycho-physiologic function, the specificity and sensitivity of the BOLD fMRI method of deception detection can rival traditional polygraph methods.
An embodiment of the present invention relates to a method for the detection of untruthful or deceptive verbal responses of a human subject. The method includes the step of performing a functional brain mapping procedure on a human subject while the human subject is speaking. The method further includes the step of determining whether the human subject is being deceptive based upon the results of the functional brain mapping.
Another embodiment of the present invention relates to a system for the detection of untruthful or deceptive verbal responses of a human subject. The system includes a functional brain-mapping device that maps brain function on a human subject while the human subject is speaking.
In some preferred embodiments the functional brain-mapping device includes a door having a penetration panel (also referred to herein as connector enclosure) with a first and second side, wherein the penetration panel has a connector 510 for attachment to a shielded data cable on the first side and a connector 510 for the attachment of a skin conductance response (SCR) cable on the second side.
Additionally, the system includes a system processor that has one or more processing elements. The system processor is in communication with the functional brain mapping device and is further programmed or adapted to receive functional brain mapping data from the functional brain mapping device and skin conductance response data from a SCR monitoring device (for embodiments including SCR monitoring) and to determine whether the human subject is being deceptive based upon the received functional brain mapping data and SCR data.
Further, the system includes a SCR monitoring device that detects SCR data of a human subject, the SCR device has an interface to a shielded data cable that transmits SCR data and an interface to a communication channel that allows communication with the system processor. The shielded data cable is also connected to the penetration panel and the SCR device shielded cable interface. A SCR cable that has at least one electrode is situated on an area on the human subject's skin, wherein the SCR cable is also connected to the penetration panel via the SCR cable connector 510.
A further embodiment of the present invention relates to a system for the SCR measurement of a human subject during magnetic resonance imaging. The system includes a system processor that has one or more processing elements in addition to a SCR monitoring device that detects SCR data of a human subject. The SCR device is interfaced to a shielded data cable, which transmits SCR data, and a communication channel that allows communication with the system processor. Further, the system is provided with a penetration panel having a first and second side, the penetration panel includes a connector 510 for attachment to a shielded data cable on the first side and a connector 510 for the attachment of a SCR cable on the second side. The penetration panel is located on a door for entry into a room that includes a magnetic resonance imaging device.
A shielded data cable is connected to the penetration panel and the SCR device shielded cable interface. Further, a SCR cable is used, wherein the SCR cable comprises at least one electrode that is situated on an area on the human subject's skin, the SCR cable connected to the penetration panel via the SCR cable connector 510.
A yet further embodiment of the present invention relates to a method for measuring the SCR of a human subject while the human subject is undergoing a MRI scan procedure. The method includes the steps of attaching at least one skin conductance electrode to an area of skin on a human subject and immobilizing that area of skin wherein the electrode is attached. Further, the method includes the steps of positioning the human subject within an MRI device and while the subject is within the MRI measuring the SCR of the subject via the skin conductance electrode and transmitting the measured SCR to a location external to the MRI device.
Additional advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.
Brief Description of Drawings The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.
Figures 1 and 1 A illustrate embodiments of a deception detection system that relates to the present invention. Figure 2 is a block diagram for a method of detection that relates to the present invention.
Figure 3 and 3A are illustrations of monitoring circuits used within embodiments of a SCR monitoring device of the present invention.
Figure 4 is an immobilizing device used within a SCR system of the present invention.
Figure 5 is a partition or door used within a SCR system of the present invention.
Figure 5A is a penetration panel used within a SCR system of the present invention. Figure 6 is a block diagram for a method for detecting the SCR of a human subject.
Detailed Description
Embodiments of the invention are described below in detail. The disclosed embodiments are intended to be illustrative only since numerous modifications and variations therein will be apparent to those of ordinary skill in the art. In reference to the drawings, like numbers will indicate like parts continuously throughout the views.
As utilized in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" include plural references also, unless the context of use clearly dictates otherwise. Additionally, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise as the term is utilized in the description herein and throughout the claims that follow.
The present invention is initially described with reference to Figure 1. Figure 1 illustrates a system 100 for the detection of untruthful or deceptive verbal responses of a human subject. The system 100 includes a functional brain-mapping device 105 that maps the brain function of a human subject while the human subject is speaking. The system further includes a door 115 having a penetration panel 118 (also referred to herein as connector enclosure) with a first and second side, the penetration panel 118 comprising a connector 510 for attachment to a shielded data cable 120 on the first side and a connector 510 for the attachment of a SCR cablellO on the second side. The SCR cable 110 has at least one electrode 106 that is situated on an area on the human subject's skin. Further provided within the system 100 is a system processor 130, wherein the system processor 130 has one or more processing elements.
The door 115 is designed to be easily and quickly installed into the threshold of a clinical magnetic resonance imaging scanner room and with use of the connector enclosure 118, pass skin conductance signals from the interior of the room to the
exterior of the room via the shielded data cable 120. Further, the door 115 serves to prevent radio frequency signals outside the room from traveling into the room through the signal wires.
The system processor 130 is in communication with the functional brain- mapping device 105 located within the room where the door 115 is installed. The system processor 130 is programmed or adapted to receive functional brain mapping data from the functional brain-mapping device 105 and SCR data from a SCR monitoring device 125. The processor further uses the acquired brain mapping and SCR data to determine if the human subject is being deceptive, as described in greater detail below.
The SCR monitoring device 125 (described in detail below) detects the SCR of a human subject and further includes an interface to the shielded data cable 120 that transmits the acquired SCR data, and an interface to a communication channel
126 that facilitates communication between the system processor 130 and the SCR monitoring device 125.
Figure 2 shows a block diagram of a method of detecting deception in a human subject that relates to the present invention. At step 305 a functional brain mapping procedure is performed upon a human subject. Functional brain mapping is applied to the subject in order to determine brain regions that experience significant activation during periods where the subject is making deceptive statements. In some alternate embodiments of the present invention, the functional brain mapping occurs during a calibration phase for determining relevant brain regions that are active during deception as compared with mapping performed during truthful response.
Real-time functional brain imaging data can be initially gathered during the calibration phase and used to initiate the detection phase. Further real-time data accumulated during the detection phase can be used as feedback to further tune the calibration phase data and enhance the ability to detect deception.
In yet a further embodiment of the present invention, no calibration phase is required; rather, real-time functional brain imaging data is accumulated during questioning of the subject. This imaging data is refined during the questioning so that the ability to detect deception improves over the course of questioning. Any suitable
functional brain imaging technique can be used including without limitation including, fMRI, BOLD fMRI, PET, SPECT, qEEG and MEG.
Additional functional brain mapping techniques used within the present invention will be described herein with the use of real-time BOLD fMRI analysis. The use of BOLD fMRI allows for the rapid interpretation of functional imaging results, even while the subject is still in the scanner performing the task. This method is very useful in the pre-surgical mapping of language areas within the brain. In its current implementations, fMRI appears sensitive enough to detect brain regions involved in many of the cognitive and emotional tasks involved in deception As illustrated in Figure 1 A, a human subject is placed in an fMRI scanner such as 1.5 Tesla Philips or Picker Edge 1.5T scanner and a structural picture of the brain is acquired. Next, a series of questions for which the questioner knows the answer are asked in which the person makes either truthful or deceptive answers. The blood flow pattern recorded during truthful statements is subtracted from the blood flow pattern recorded during deceptive statements. Previous research has found significant activation in the right orbitofrontal and/or cingulate regions of the brain during periods of deception; however, other brain regions can be of significance as well. Using real-time functional image analysis, the area(s) of activation in the brain for that person during deception is identified. A test of one embodiment of the present invention was performed using eight male test subjects. The mean age of the subjects was 25 years old, with a range of 21- 28 years of age. The subjects had no significant history of psychiatric or medical problems. Average Annett Handedness score for right-handedness was 11 with a range of 9 to 12 While the BOLD fMRI scans of the test subjects were being acquired, a modified control question test paradigm was utilized in which the subjects would give both truthful and deceitful answers about the location of the money. Through video goggles connected to a computer, the subjects were shown prompt screens and then pictures of the objects in the rooms where the money had been hidden. If the subjects first looked in a "TRUTH" room, then they were shown only the TRUTH room objects first and then a "DECEPTION" room objects and vice versa if subjects were
first shown the DECEPTION room. There were five objects in each room (ten unique objects in all), and the objects were each shown one time in a block for a total of four blocks per room.
The order of the objects was randomized within each block. The order of room/image presentation was randomized. Before the picture of the first object and between the pictures of every object in the room, a PROMPT screen was displayed that reminded the subjects of the instructions. The object and the PROMPT were each displayed for 10.2 seconds. Subjects were instructed to raise either one (yes) or two (no) fingers to answer the question of whether the money was hidden under an object as soon as the object was visually displayed in the goggles. This was monitored and recorded by an observer.
For the TRUTH room, subjects were instructed to accurately report the location of the money by holding up the right index finger (one finger) when they were shown an object under which the money had been hidden. This would be the "control" with which the deceptive answers would be compared. This control for the potential confounds of brain changes associated with simply seeing an object that had money under it. They were instructed to raise the right index and middle finger (two fingers) when shown an object under which the money was not hidden.
For the DECEPTION room, they were too instructed to choose an object that did not have money hidden under it and respond affirmatively (right index finger), in effect creating a positive lie about the money location. They were also asked to respond negatively (right index and middle finger) to all other objects shown. They were thus consistently lying when the object with money hidden under it was shown (a hat). The money was hidden under the same object for all subjects. Subjects were told that a blinded investigator (to order of rooms visited and location of the money) would attempt to determine when they were lying by observing their behavior in the scanner through the control room window. If the subjects accurately reported the position of the money in the TRUTH room, then they would receive 50 dollars. If the subjects "successfully" lied without being detected for the DECEPTION room, then they would receive an additional 50 dollars. All of the test subjects were paid the full
100 dollars, this instruction was included in order to increase the motivation and the anxiety of the subjects during deception.
MRI images can be acquired using a Picker Edge 1.5T MRI scanner equipped with an actively shielded magnet and high performance whole-body gradients (27 mT/m, 72 T/m-sec). A 15 -slice TE20 structural scan can be obtained to evaluate for any structural pathology. The BOLD fMRI can consist of 15 coplanar transverse slices (8.0 mm thick/0 mm gap) covering the entire brain and positioned 90 degrees to the Anterior Commissure-Posterior Commissure line using a sagittal scout image. Each fMRI volume can consist of BOLD weighted transverse scans and used an asymmetric-spin gradient echo, echo-planar (EPI) fMRI sequence (tip angle=90° to the Anterior Commissure-Posterior Commissure line; TE 45.0 ms; TR 3000 ms; fifteen 8 mm thick / 0 mm gap transverse slices; FON 300 x 300 mm; in-plane resolution 2.109 x 2.109 mm; through-plane resolution 8 mm; frequency selective fat suppression). Given these parameters for the fMRI, a set of fifteen 8 mm thick / 0 mm gap transverse slices covering the entire brain can be obtained every 3 seconds. Group analysis for Lie minus Truel
Image maps of the functional neuroanatomy involved in deception were generated. Within individual statistical maps to test for individual heterogeneity and the predictive power of imaging to detect deception were generated. Lie minus Truel is the subtraction that best isolates the act of deception by controlling for most confounds. The orbitofrontal cortex (OFCx) and anterior cingulate (AC) regions of the brain were found to be significant in the deception process. The data appears in table 1 below:
Table 1
Individual Analyses for Lie minus Truel
The heterogeneity among subjects in brain activation during the deception task was examined. Each individual was examined to determine if they had significant activation in any of these regions during the deception minus true comparison. Using a minimum statistical threshold of z=1.645 and extent threshold of 0.05, one subject had no significant activation, while seven others showed diverse activation patterns. No one brain region was found activated for all subjects when True epochs were subtracted from Lie epochs. The mean number of discrete regions identified by the
group analysis that were activated by individuals was 2 per individual subject with a range of 0 to 6. fMRI Analysis
At step 310 of Figure 2, a determination is made based upon the acquired BOLD fMRI data whether the human subject is being deceptive. The data in the exemplary test discussed herein was analyzed with both MEDx 3.3/SPM96. Initially, the MEDx motion detection function was performed using the center of intensity weighting method. Any motion greater than 2.0 mm would have been corrected using the MEDx 3.3 motion correction function (no subjects required motion correction). Next, individual volumes were spatially normalized into Talairach space utilizing the SPM Module 96 in MEDx 3.3. Algorithm parameters included Basic functions and smoothing x=4, y=5, z=l, iteration=2, smoothing=8.0, deformation=0.2, the SPM template corresponding to the original Talairach and Toumoux atlas (Talairach 1988) and output voxel size 4x4x4 mm. Using the SPM module again, spatial smoothing was performed using 8xSx8 mm gaussian kernel. Intensity normalization was performed which first created a with-in-the-brain mask that only included voxels if they had intensity > 35% the maximum of each image volume for all time points and then scaled the remaining non-zero voxels in each volume in the time series to a mean value of 1000. Next, high pass temporal filtering was performed in order to filtere out patterns greater than twice the cycle length of 204 seconds. Due to the SPM module performing another intensity mask during the upcoming SPM statistics step, a .tel script was written to add 100 to all voxels outside the brain. When the SPM statistics was run, this ensured that no voxels we previously defined as within brain would be eliminated from the analysis but that voxels we previously defined as outside the brain would be eliminated.
Using the SPM module on MEDx 3.3, statistical analysis with a delayed boxcar design without temporal filtering was performed. The first run grouped the epochs as Lie (the time period when individuals gave a false answer - both indicating that the object did not conceal money when it did {4 epochs} and indicating the object concealed money when it did not {4 epochs}), Lprompt (time period prompt image
displayed just prior to each Lie {8 epochs}), True! (time period subjects answered truthfully the location of the money {4 epochs} and 4 truthful answers that the money was not under an object -temporally surrounding deceptive answers {4 epochs}), Prompt! (time period prompt displayed immediately preceding Truel epochs), True (time period of all remaining truthful answers . {24 epochs}), and Prompt (time period of prompt immediately preceding True epochs {24}). Using these epochs, Lie minus True 1 and True 1 minus Lie was computed with no threshold (p=0.05 and uncorrected k (cluster size) = 1). The individual unthresholded images were used to obtain a group and individual statements. To make a group statement, for all individuals the image calculator in MEDx
3.3 was used to make unthresholded Lie minus Truel z-maps containing both positive and negative z-scores. Thus, the result of (Lie minus Truel) minus (Truel minus Lie) z-maps was obtained for each subject. Once this data was gathered for all individuals, it was summed and divided by the square root of eight to create a group fixed effects analysis unthresholded z-map. The resulting image was then analyzed with MEDx 3.3 cluster detection with a minimum of z=1.645 and spatial extent threshold of 0.05. The resulting values were used to determine local maxima and visually present the significant clusters. The Talairach Daemon interface in MEDx 3.3 was used to identify locations of the local maxima. For the individual subject's analysis, the unthresholded images of True 1 minus
Lie were subtracted from Lie minus Truel. The resulting image was analyzed using MEDx 3.3 cluster detection with a minimum of z=1.645 and extent threshold of 0.05. The resulting values were used to determine local maxima and make a visual representation of those significant clusters. The Talairach Daemon interface was used to identify location of the local maxima. This was performed for each individual.
A second group analysis was performed with the differently defined epochs. The epochs were labeled Lie (time period individuals gave a false answer both indicating object did not conceal money when it did {4 epochs} and indicating the object concealed money when it did not {4 epochs}), Lprompt (time period prompt just prior to each lie was displayed {8 epochs}), True (time period of all true responses {32 epochs}), and Prompt (time period of all prompts preceding True {32
epochs}). With the above epochs, Lie minus Lprompt, Lprompt minus Lie, True minus Prompt, and Prompt minus True were computed for each individual using MEDx 3.2 with no threshold. The resulting images were utilized to make group statements using the same method as described above. This completed the neuroimaging analysis.
The MMPI-2 is one of the most widely used self-report measures in assessing psychiatric symptoms. It is a standardized 370-item true-false questionnaire that elicits a range of self-descriptions to measure emotional adjustment and test-taking attitude. There are 13 basic scales, of which 10 relate to clinical/personality and 3 to validity indices. Additionally, a variety of content and supplementary scales exist.
The MMPI-2's Scale 4 (Psychopathic Deviate) was developed as a measure of antisocial tendencies or psychopathic behavior, and was created based on a criterion group of young persons diagnosed with a psychopathic personality and delinquent behavior. High scores tend to be obtained in deviant groups such as delinquents, prisoners, and shoplifters, while moderate elevations may be present in unconventional individuals willing to take risks.
The MMPI-2 Pd scale was correlated with total number of voxels activated in significant clusters using StatView 5.0.1. The number of voxels per individual was obtained with the cluster detection function in MEDx 3.3. The number of voxels was the sum of significantly (z > 1.645) activated voxels in clusters that met spatial extent threshold of 0.05. The Fisher's r to z (p value) and correlation coefficient were calculated.
Deception minus Prompt The areas of significant activation for Lie minus Lprompt in order of significance by z-score were, on the right, the inferior, middle and superior frontal gyms, anterior cingulate gyms, medial frontal gyms, and the left superior frontal gyrus. True minus Prompt
The areas of significant activation for Tree minus Prompt in order of significance by z-score were posterior lobe of the right cerebellum, left cingulate gyms, left superior frontal gyms, left medial frontal gyms, right middle frontal gyms, right superior temporal gyms, right inferior frontal left middle frontal gyms, and anterior lobe
culmen. Deception minus True
This is the subtraction that best isolates the act of deception by controlling for most confounds. The areas of significant activation for Lie minus True 1 in order of significance by z-score were left middle temporal gyms, right precentral gyms, right middle frontal gyms, left posterior lobe cerebellum, right superior frontal gyms, left superior temporal gyms, left inferior temporal gyms, left anterior lobe cerebellum, right inferior frontal gyms, right medial frontal gyms, and right anterior cingulum.
The areas of significant (z=1.645, extent threshold=0.05) activation for True minus Deception in order of significance by z-score were left superior frontal gyrus, left precentral gyms, left middle frontal gyrus, and left superior occipital gyms. Skin Conductance Response
As illustrated in Figures 1 and 1 A, embodiments of the present invention can combine the results of a SCR monitoring system 125 concurrently with the results of a BOLD fMRI 105 scan in order to detect deception in a human subject. The SCR system 140 has a SCR monitoring device 125, wherein the SCR monitoring device further includes a SCR monitoring circuit 300 (Figure 3). Additionally, the SCR system 140 can include in some embodiments a partition or door 115 including a connector enclosure also referred to herein as a penetration panel 118 (Figure 5), wherein the penetration panel has a first and second side. The penetration panel 118 comprises a connector 510 for attachment to a shielded data cable 120 (Figure 5 A) on the first side and a connector 510 for the attachment of a SCR cable 110 on the second side. The SCR cable 110 has at least one electrode 106 that is situated on an area on the human subject's skin. The door 115 is composed of an electrically conductive panel having two sides. The, panel can be of any appropriate shape to fit in potential doorways, typically rectangular. Electrically conductive contact strips attached to the panel and distributed around its periphery provide a shielding seal and a mechanical seal between the panel and the doorway. The panel includes one or more electrical connectors on both sides of the panel allowing signals carried on the first side to pass to the second side.
The panel can be composed of a single piece, or alternatively, can include multiple pieces assembled together. In some preferred embodiments, the panel is compose of at least in part of a translucent or transparent material allowing a person outside the room to assess what is going on in the room, referred to herein as a substantially transparent material.
Some embodiments may include one or more handles to allow for ease of access. In some embodiments, the door may be fixedly attached to the doorway via known techniques such as with hinges. Alternatively, the one or more handles can be used for easy installation and removal of the door from the doorway in embodiment not using a fixed mounting of the door to the doorway.
The connectors are preferably mounted in a connector enclosure 118. Some embodiments of the connector enclosure can provide for filtering of the signals received at the first side connector and passed to the second side connector. The filtering can be of any known type including not only the capacitors shown in the illustrated embodiment but also other passive elements such as inductors, active elements such as amplifiers and combinations thereof.
The system processor 130 is in communication with the functional brain- mapping device 105. The system processor 130 is programmed or adapted to receive SCR data from the SCR monitoring device 125. The processor 130 further uses the acquired brain mapping and SCR data to determine if the human subject is being deceptive.
The SCR monitoring device 125 detects the SCR of a human subject and further includes an interface to the shielded data cable 120 that transmits the acquired
SCR data and an interface to a communication channel 126 that facilitates communication between the system processor 130 and the SCR monitoring device
125.
Figure 3A shows an embodiment of a SCR monitoring circuit that may be used with embodiments of the present invention. The range of human SCR magnitudes is from SCRmin~0.01μS to SCRmax~lμS. In order to ensure adequate resolution in measuring the smallest conductance responses, we required the SCR monitoring system to suppress interference during fMRI to a level σ an order of
magnitude below SCRπ σ = SCRmin /10=10-3 μS This can be accomplished by using a low-pass filter with cutoff frequency of 1 Hz (5), because SCR signals change relatively slowly compared to interference generated by the MR scanner. Figure 3A shows the schematic diagram of the SCR monitoring circuit consisting of a Wheatstone bridge 305, a differential amplifier 310, and low- pass filter 315. Rl of the bridge 305 is a 10-turn potentiometer, and all fixed resistors have 1% tolerance. The bridge output ΔVout (between points C and D of Fig. 3 A) is proportional to the change in the subject's skin conductance ΔC4, as given by ΔV„ut = Nin^ Eqn. (l)
C_ wherein C
3=l/R
3=5000 μS, and Vi
n=0.488 V is the voltage from A to B, regulated by the reference diode. If one inserts the component values into Eqn. (1) and uses the lower limit of human SCR amplitudes
one finds an expected minimum bridge output voltage of ΔV
mi
n=l μV. For determining adequate amplifier gain G, the minimum of 10 voltage steps V
res must be present over the lower limit of amplified output voltage GΔV
mm, or GΔV
mi
n/Vres>l 0, yielding for G the criterion, the gain should satisfy O>610.
10F G ≥ — - - Eqn. (2) V ' mi ■n ■
The amplifier 310 output is fed to a low-pass filter with a 3 dB cutoff frequency of 1 Hz. Voltage supplies ranging from +6 to -+18 V may provide power to the amplifier and filter circuits. The resistor R5 limits current through the reference diode, which maintains a constant voltage of 1.22 V, and satisfies
R5(kΩ) ≥ V + ~ 22V Eqn. (3)
5 ; 50mA
Embodiments of the SCR system 145 can include an immobilizing device 400 as illustrated in Figure 4. The immobilizing device 400 fits over the subject's wrist, thereby minimizing movement of the wrist, leads, and electrodes 106. The immobilizing device 400 maintained a uniform pressure on the electrodes 106, thus
reducing the chances of variations in conductance caused by disturbing the contact between the electrodes 106 and the subject's skin. The immobilizing device is constructed from a 25.4 cm (10 in) length of PNC pipe 10.2 cm (4 in) in diameter. The pipe was cut in half lengthwise, and padded with foam. A rectangular piece of 0.64 cm (0.25 in) thick Lexan sheet 10.2 x 16.5 cm (4x6.5 in) was covered with foam, and mounted across the pipe with adjustable nylon bolts so that a constant, uniform pressure could be applied to the electrodes as they rested against the palm of the hand. The electrode leads were twisted together to reduce currents induced by the scanning gradients, and comiected to non-ferrous, snap-on ECG connectors. The electrode leads were then soldered to a length of shielded, twisted-pair cable long enough to reach from the center of the scanner to the door, and terminated with a twin BΝC connector 510. The cable was permanently attached to the immobilizer in such a way that a pull on the cable would not put stress on the electrode leads. The door 115 used with the SCR system 145 is used to prevent the SCR cable
110 from picking up outside radio frequency (RF) interference and transferring the RF interference into the scan room and thus degrading the quality of the fMRIs. The door 115 is assembled from aluminum angle irons cut to the dimensions of a specified doorway, with allowance made on the sides and top for the addition of metal contact fingers compressed 70% of their width. The lower half of the door 115 is covered with an aluminum plate 0.64 cm (0.25 in) thick, and the upper half with aluminum screen. Aluminum side handles were added to make moving the door easier. The penetration panel 118 comprises a twin BΝC connector 510 mounted to the aluminum plate to mate with the SCR cable 110 on the immobilizing device 400. A filtered penetration port is mounted to the aluminum plate consisting of an interior aluminum bulkhead through which two 400 Hz, low-pass, feed-through capacitors 520 are mounted.
Figure 1 illustrates. the shielded cable 120 used within the SCR system 145. Shielding -the cable with braided copper sheath is used to further reduce fMRI scanner interference. This established a ground connection between the chassis of the electronics box, the custom-built aluminum door, and the scan room shielding, and
reduced interference considerably.
Figure 6 is a block diagram detailing a yet further embodiment of the present invention that relates to a method for measuring the skin conductance response of a human subject while the human subject is undergoing a magnetic resonance imaging (MRI) scan procedure. At step 405 at least one skin conductance electrode is attached to an area of skin of a human subject. The area of skin to which the electrode is attached is immobilized at step 410. Further, at step 415, the subject is positioned within an MRI device. Next, while the subject undergoes fMRI, the SCR of the subject is measured as the subject verbally responds to questions. Lastly, at step 425, the SCR data is transmitted to a location external to the MRI device. SCR Analysis
As shown in Figure 1, a SCR device 125 can be used concurrently with a MRI scanning device 105 in order to accumulate sufficient data to either prove or disprove the deception of a test subject. Some embodiments can use electrodermal electrodes attached to the left hand and the data (sampling rate 100 per second) recorded.
In order to correlate EDA with the functional BOLD signal, MEDx 3.3 analysis package requires an equal number of volumes and SCR data points. The SCR data corresponding to each volume (TR = 3 seconds) was therefore averaged using STATA. Thus, every sequential 300 EDA data points (sampling rate was 100 per second) were averaged to give 272 means that corresponded to the firactional brain volumes to be compared. The volumes utilized were the ones that had been motion detected, spatially normalized, smoothed, intensity normalized, and temporally filtered. Using MEDx 3.3, independent of the deception paradigm, the changes in SCR. were correlated with BOLD fMRI changes using a Pearson's r coiTelation. This analysis, was perfonned for each individual resulting in a. z-map. One of the coiTelation z-maps. was found to have a significant artifact and was not included in the individual or group analysis.
For the GROUP analysis, the remaining seven individual z-maps were added using the MEDx 3,3 calculator and divided by the square root of seven. The resulting image was then analyzed with MEDx 3.3 cluster detection with a minimum of z=1.960 and spatial extent threshold of 0.05. In the direct BOLD comparison above
(Lie minus Truel), we were only able to use eight epochs. This study is thus underpowered relative to many in the field. For the correlation analysis, we were able to use all time points, and we were justified in using a larger z value threshold. The resulting values were used to determine local maxima and visually present the significant clusters. The Talairach Daemon interface in MEDx 3.3 was used to identify locations of the local maxima32.
For the INDIVIDUAL analysis, the individual correlation z-maps were each analyzed using MEDx 3.3 cluster detection with a minimum of z=1.960 and extent threshold of 0.05. The resulting values were used to determine local maxima and generate a visual representation of those significant clusters. The locations of the significant clusters were determined using the same technique as the group analysis. Group Analysis Correlating EDA Changes and BOLD- fMRI Changes
For the group analysis, one of the subjects had significant artifact after the correlation analysis and was not included in the group analysis. Significant activation was found in the orbitofrontal and right anterior cingulate gyrus. The analysis of this data appears in table 2 below.
Table 2
This data demonstrates a link between EDA changes during deception and
OFCx and AC activation.
Individual Analysis Correlating EDA and BOLD- fMRI Changes
Of the seven subjects (one subject with significant artifact), six had significant
(z >1.960 and extent threshold < 0.05) right orbitofrontal activation (see Figure 4), and five had significant (z >1.960 and extent threshold < 0.05) right anterior cingulate activation. No other regions consistently activated across individuals.
Other aspects of the invention may be found from the attached drawings and other related materials such as a detailed review of the various functions offered by the present invention, which are integral parts of this disclosure. Moreover, other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.