RU2231293C1 - Method for determining stimulation time for human visual analyzer - Google Patents

Abstract

FIELD: medicine, ophthalmology.

SUBSTANCE: the present method deals with sequence of paired light impulses of duration being 200 msec divided by inter-impulse interval being equal to 70 msec repeated every constant time interval of 1 sec. Duration of inter-impulse interval between light impulses in pair should be shortened till patient could detect the moment for subjective fusion of two light impulses in pair into one. Duration of inter-impulse interval between light impulses in pair at the present moment is considered to be the stimulation time for human visual analyzer.

EFFECT: more simplified measuring technique and increased accuracy.

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Description

The invention relates to medicine and is intended to determine the time of excitation of the human visual analyzer.

A known method of determining the threshold time required for recognition of the presented images using a tachistoscope [1].

A known method for determining the duration of photochemical processes in the receptors of the human retina, based on the assessment of differences in the latent period of a simple sensorimotor reaction of the test subject to adequate (diffuse flash of light) and inadequate (electrical stimulation - “phosphenes”) light stimuli. Before starting the experiments, adequate and inadequate light stimuli are aligned according to “subjective brightness” [2].

A known method for assessing the functional state of the color vision apparatus by exposing the eye to a pulsed light source of the visible range of the spectrum and then measuring the critical flicker fusion frequency, characterized in that at least four pulsed radiation sources of different wavelengths with a fixed peak brightness are sequentially exposed to the eye monocularly the duty cycle of 0.5, set the distance of the eye from the light source to 300-330 mm, a color stimulus is presented three times with a color spot diameter of 9-1 0, 2.2-2.5, 1.0-1.2 mm, at each presentation of a color stimulus, the spectral critical frequency of flicker fusion is determined and from the measured values on this characteristic for each color with a stimulus diameter of 1.0-1.2 mm establish an individual initial level of excitation and the color perception rate of the apparatus of color vision, with a diameter of 9-10 mm - the individual upper limit of excitation of the apparatus of color vision, and with a diameter of the stimulus of 2.2-2.5 mm - the level of the current state of the apparatus of color vision of the subject [3 ].

The disadvantage of this method is the duration of the study, the inability to determine the time of excitation of the human visual analyzer.

None of the known methods can be adopted as a prototype to the proposed method for determining the time of excitation of the human visual analyzer.

The proposed method for determining the time of excitation of the human visual analyzer allows you to:

- simplify the procedure for determining the time of excitation of the visual analyzer of a person,

- reduce the time for determining the time of excitation of the human visual analyzer, which will reduce the fatigue of the visual analyzer and thereby increase the measurement accuracy.

The proposed method for determining the time of excitation of a human visual analyzer is that a subject is presented with a sequence of paired light pulses of a given duration equal to 200 ms, separated by an interpulse interval of 70 ms, repeated through a constant time interval of 1 s, and at the first stage of measurements, the duration of the interpulse interval between light pulses in a pair is reduced at a given constant speed of 20 ms / s, until the subject determines the moment of subjective fusion of two light pulses paired in one, at the second measurement stage, the duration of the inter-pulse interval between light pulses in a pair is increased at a given constant speed of 2 ms / s, until the subject determines the moment of subjective sensation of the separation of two light pulses in a pair, at the third measurement stage, the duration of the inter-pulse interval between light pulses in a pair is reduced discretely with a given constant step of 0.1 ms, until the subject determines the moment of subjective merging of two light pulses in a pair into one, the time of excitation of the visual analyzer is taken equal to the value of the duration of the interpulse interval determined by the subject at the third stage of measurement.

Figure 1 presents a timing diagram of a sequence of paired light pulses presented to determine the excitation time of the visual analyzer.

Figure 2 presents the timing diagram of the change in the duration of the interpulse interval between light pulses in a pair when determining the excitation time of the visual analyzer.

Figure 3 presents the timing diagrams of two light pulses of duration τ _imp , separated by the interpulse interval t of the _mission , and the visual sensations caused by them, where:

- figure 3, a is a timing chart of two light pulses separated by an interpulse interval t of the _mission - causing a visual sensation of separation of pulses;

-Fig. 3, b is a timing diagram of the visual sensation of two light pulses shown in figa;

- figure 3, c is a timing chart of two light pulses separated by a threshold inter-pulse interval t _then , at which a subjective sensation of fusion of two light pulses in a pair into one is achieved;

-fig.3, g is a time diagram of the visual sensation of two light pulses shown in figv;

- τ _on is the time of on-system excitation of the visual analyzer — the summation time of the on-system is necessary for the visual sensation of the onset of the stimulus to occur, that is, the time between the moment of light exposure on the retina and the moment the corresponding visual sensation occurs [4, 5, 6] (Fig. .3, b);

- τ _off - the excitation time of the off-system of the visual analyzer is the summation time of the off-system, necessary for the appearance of a visual sensation of the end of the stimulus (Fig.3, b).

The proposed method for determining the time of excitation of the human visual analyzer is as follows.

The test subject is presented with a sequence of pair of light pulses of a given duration τ _imp equal to 200 ms, separated by an initial interpulse interval of duration t _nmi equal to 70 ms, repeated through a constant time interval T equal to 1 s (Fig. 1; Fig. 2, time interval T ₀ -T ₁ ).

At the first stage of measurements, the duration of the initial interpulse interval t _nm between the light pulses in a pair is reduced with a given constant speed v ₁ equal to 20 ms / s (Fig. 2, the time interval T ₁ -T ₂ ), until the subject determines the moment of subjective fusion of two light pulses in a pair of one (figure 2, time T ₂ ).

At the second stage of measurements, the duration of the interpulse interval t of the _mission between the light pulses in a pair is increased with a given constant speed v ₂ equal to 2 ms / s (Fig. 2, the time interval T ₃ -T ₄ ), until the subject determines the moment of subjective sensation of separation of the two light pulses in a pair (figure 2, time point T ₄ ).

At the third stage of measurements, the duration of the interpulse interval t of the _mission between the light pulses in a pair is reduced discretely with a given constant step of 0.1 ms (Fig. 2, the time interval T ₅ -T ₆ ) until the subject determines the moment of subjective fusion of two light pulses in a pair in one (figure 2, point in time T ₆ ).

The interpulse interval t of the _mission between the light pulses in a pair, at which a subjective sensation of the fusion of two light pulses in a pair into one is achieved, is taken as the threshold interpulse interval t _then . The excitation time of the visual analyzer is taken equal to the value of the duration of the threshold interpulse interval t _then determined by the subject at the third measurement stage.

The excitation time of the visual analyzer can be determined by the minimum duration of the light pulse perceived by the subject. However, it was experimentally established that when the duration of light pulses is less than 3 ms, the intensity of subjectively perceived radiation decreases. An increase in radiation intensity to a normal subjectively perceived level is undesirable due to possible damage to the retina of the visual analyzer [7].

At the same time, it is known that on- and off-systems, which respectively generate a signal about the appearance and end of a light stimulus in a visual analyzer, function independently of each other [8, 9], and their dynamics are similar [10]. This makes it possible to determine the excitation time of the visual analyzer, that is, the on-system, by the equal time of the excitation of the off-system.

Upon presentation to the subject of two light pulses of duration τ _imp > τ _on , separated by an interpulse interval t _mission > t _then (Fig.3a), the off-system of the visual analyzer is excited after the end of the first impulse and generates a signal indicating its end, therefore, the subject appears subjective sensation of separation of two light pulses (Fig.3, b).

With a decrease in the duration of the inter-pulse interval between two light pulses, the perception of visual pulses is more difficult due to the influence of reverse masking, which consists in a deterioration in the perception of the first time pulse due to the presentation of the second pulse in the immediate spatio-temporal proximity with the first, as well as direct masking, in which the first pulse affects the quality of perception of the second [11]. Therefore, when the duration of the interpulse interval t of the _mission between two light pulses decreases to the value of t _mission = t _then (Fig.3c), the off-system of the visual analyzer after the end of the first pulse does not have time to get excited and generate a signal indicating its end, and the subject has a feeling subjective fusion of two light pulses into one (Fig.3, g).

The duration of the threshold interpulse interval t of _pores between two light pulses, at which a subjective sensation of the fusion of two light pulses into one is achieved, determines the threshold value of the excitation time of the off-system or an equal threshold value of the excitation time of the on-system of the visual analyzer.

During responses to light stimuli, the receptive field (RP) of a small neuron appears first. Then, the recorded RP expands, after which it weakens, fragmentes, and disappears. A statistical evaluation showed that the disappearance of the registered RP neuron occurs in the period from 100 to 200 ms after the appearance of the light stimulus [10]. After the disappearance of RP, neural structures return to their original state and become ready to accept a new stimulus [12], therefore, the duration of light pulses is taken to be 200 ms.

Since the formation of the RP excitation zone ends in 60–70 ms after the presentation of the light stimulus [12], the duration of the interpulse interval is taken to be 70 ms. With such a duration of the inter-pulse interval, the on-system of the visual analyzer after the end of the first light pulse is excited and generates a signal indicating its termination.

With an interstimulus interval of 500 ms, masking effects are absent or weakly expressed | 13 |. To eliminate the masking effect, the sequence of paired light pulses is repeated at a constant time interval of 1 s.

Thus, the inventive method for determining the time of excitation of the visual analyzer of a person has new properties that determine the receipt of a positive effect.

Example. Subject S., 20 years old, using a personal computer compatible with IBM PC that _{outputs light flickers} through the LPT port to the indicator of the subject's remote control, showed a sequence of paired light pulses of duration τ _imp equal to 200 ms, separated by an initial interpulse interval of duration t _nm equal to 70 ms repeating through a constant time interval T of 1 s (FIG. 1; FIG. 2, time interval T ₀ -T ₁ ).

In the process of measurement through the LPT port, the signals from the buttons "Decrease fast", "Increase slow", "Decrease discrete" and "Measurement" were sent to the personal computer from the test subject's remote control.

In the presence of a signal from the “Decrease fast” button, the computer reduced the duration of the inter-pulse interval between light pulses paired with a speed v ₁ equal to 20 ms / s, if there was a signal from the “Increase slow” button, it increased with a speed v ₂ equal to 2 ms / s, if there is a signal from the "Decrease discrete" button, it decreases discretely with a constant step of 0.1 ms.

At the first stage, the test subject, giving a signal from the button "Decrease fast" (figure 2, the time interval T ₁ -T ₂ ), estimated the moment of subjective fusion of two light pulses in a pair into one (figure 2, time T ₂ ).

In the second stage, the test subject, giving a signal from the button "Increase slow" (figure 2, the time interval T ₃ -T ₄ ), determined the moment of subjective sensation of the separation of two light pulses in a pair (figure 2, time T ₄ ).

At the third stage, the test subject, giving a signal from the "Discrete Decrease" button (Fig. 2, time interval T ₅ -T ₆ ), determined the moment of subjective merging of two light pulses in a pair into one (Fig. 2, time moment T ₆ ), then gave a signal from the button "Measurement" (figure 2, time T ₇ ).

The computer determined the duration of the interpulse interval t of the _mission between the light pulses in the pair, recorded by the subject at time T ₆ (Fig. 2), which is the duration of the threshold interpulse interval t of _pores , taken as the time of excitation of the visual analyzer. Next, the computer displayed the value of the time of excitation of the human visual analyzer on the monitor screen, entered the measurement result in the archive and presented the initial sequence of paired light pulses.

In accordance with the recommendations of physiologists, the subject performed a series of 10 measurements. As a result of measurements, the following values of the time of excitation of the visual analyzer of the test person in ms were obtained: 10.6; 10.0; 10.1; 10.0; 10.5; 10.3; 10.0; 9.8; 10.1; 10.0 The arithmetic mean of the measured values of the excitation time of the human visual analyzer is 10.14 ms, the standard deviation is 0.08 ms, the confidence limits of the random component of the error of the measurement result with a confidence probability of 0.95, taking into account the student coefficient, 0.185 ms.

Thus, the proposed method allows to determine the value of the excitation time of the human visual analyzer.

Sources of information

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Claims (1)

A method for determining the excitation time of a human visual analyzer, which consists in the fact that the test subject is presented with a sequence of pair of light pulses of a given duration, repeating through a constant time interval, and at the first stage of measurement, the duration of the inter-pulse interval between light pulses in a pair is reduced with a given constant speed of 20 ms / s until the subject determines the moment of subjective fusion of two light pulses in a pair into one, at the second stage of measurements, the duration between the pulse interval between light pulses in a pair is increased at a given constant speed until the subject determines the moment of subjective sensation of the separation of two light pulses in a pair, at the third stage of measurement, the duration of the inter-pulse interval between light pulses in a pair is reduced until the subject determines the moment of subjective fusion of two light pulses pulses in a pair in one, the excitation time of the visual analyzer is taken equal to the value of the duration of the interpulse interval, defined and interrogated at the third stage of measurements, characterized in that the duration of the pair of light pulses presented to the test person is 200 ms, the interpulse interval is 70 ms, the paired light pulses are repeated after 1 s, and at the second stage of the measurements, the duration of the interpulse interval is increased at a speed of 2 ms / s, and at the third stage of measurements, the duration of the interpulse interval is reduced discretely with a given constant step of 0.1 ms.

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