RU2252701C1 - Method for determining human vision system persistence time - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: method involves showing sequence of two luminous pulses of 10 ms duration separated by 150 ms long pause. The pulses are repeated in constant 1.5 s long interval. Pause duration between two luminous pulses is reduced at the first measurement stage at constant speed of 20ms/s until a testee fixes fusion of two luminous pulses into single one in subjective assessment mode. Pause duration between two luminous pulses is increased at the second measurement stage with given constant step of 0.4 ms until the testee identifies the moment of subjective perception of two luminous pulses separation. Pause duration is reduced in discrete mode with given constant 0.1 ms long step at the third measurement stage until the testee identifies the moment of subjective perception of two luminous pulses fusion into single one. Human vision system persistence time is determined to be equal to pause duration between two luminous pulses when subjective fusion into single pulse takes place at the third measurement stage.

EFFECT: high accuracy in determining human vision system persistence time.

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Description

The invention relates to medicine and is intended to determine the time of inertia of the human visual system.

A known method of determining the time of inertia of vision using a pendulum and contrast filters [1]. Using this method, the threshold contrast ε is measured for a given object during stationary observation, then, at different contrasts K _p created by a given set of filters, the effective contrast K _{e is} brought to the visibility threshold by selecting the exposure time τ specified by the swing amplitude of the pendulum. For the time of inertia, the effective time of preservation of the visual impression is taken, which at the exposure time τ <0.01 s is determined by the formula

θ = K _p τ / ε.

The disadvantage of this method is the use of the mechanical principle of setting the exposure time, which reduces the accuracy of determining the time of inertia.

A known method of tachistoscopy to measure the threshold time required to recognize the presented images [2]. The threshold image recognition time depends on the inertia parameters of the visual system [3]. According to this method, a fixation point is projected in the center of the pre-exposure field, which is used as a ready signal. The fronts of the exposure field are 1.5–2.0 ms. Exposure times vary using an electronic device with a minimum step of 1.5 ms.

The disadvantage of this method is its complexity and low accuracy of measuring the threshold time for image recognition due to the extended edges of the exposure field, which, when the stimuli are presented for about 10 ms, is no less than 3-4 ms.

Known studies of the inertia of the human visual system using electroretinography and visual evoked cortical potentials [4, 5].

A common disadvantage of the methods is the long preparatory period before research, the need to use special equipment, the complexity of the research behavior.

Closest to the technical nature of the proposed method is a method for determining the time of inertia of the human visual system by presenting the subject with light pulses, which consists in the fact that the subject is presented with a sequence of two light pulses of a given duration equal to, for example, 50 ms, separated by a pause equal to, for example, 150 ms, repeated after a constant time interval of the order of 1.5 s, the pause duration between light pulses is reduced until the subject determines the moment of sub objective merging of two light pulses into one, and at the first stage of measurement, they reduce the pause duration between two light pulses with a given constant speed of about 20 ms / s, until the subject determines the subjectively merging of two light pulses into one, and at the second measurement stage, increase the pause duration between two light pulses with a given constant speed of the order of 5 ms / s, until the subject determines the moment of subjective sensation of separation of two light pulses, in the third stage of of measurements reduces the duration of the pause between two light pulses with a given constant speed of the order of 2 ms / s, until the subject determines the moment of subjective merging of two light pulses in one, the time of inertia of the human visual system is taken equal to the value of the duration of the pause between two light pulses at the moment of subjective merging of two light pulses in one determined at the third stage of measurement [6].

The disadvantage of this method is:

- the impossibility of determining the time of inertia in the absence of a signal generated by the off-system about the end of the light pulse. It is known that at all levels of the visual system there are two different signal transmission paths: the direct path and the signal transmission path through horizontal connections. Excitation is transmitted along a direct path from level to level, and inhibitory-excitatory interaction between neurons at each level of the visual system occurs along horizontal connections. In this case, the inhibitory process occurs 15–20 ms later than the excitatory one; therefore, with a pulse duration shorter than 15–20 ms, the off-response of neurons does not occur [7, 8]. For this reason, the inertia time with a pulse duration of less than 15-20 ms is determined in the absence of a signal generated by the off-system to end the light pulse, while with a light pulse duration of 50 ms, the inertia time is determined in the presence of an off-response ;

- low accuracy in determining the time of inertia, since the determination of the moment of subjective merging of two light pulses into one occurs with a continuous change in the duration of the pause, that is, under conditions of continuous adaptation of the visual system to a continuously changing parameter.

The proposed method for determining the time of inertia of the human visual system allows you to:

- determine the time of inertia of the human visual system in the absence of an off-response about the end of the light pulse.

- increase the accuracy of determining the time of inertia of the visual system.

The proposed method for determining the time of inertia of the human visual system, which consists in the fact that the test subject is presented with a sequence of two light pulses of a given duration, separated by a pause of 150 ms, repeated through a constant time interval of 1.5 s, and at the first stage of measurement, the duration of a pause between two light pulses with a given constant speed of 20 ms / s, until the subject determines the subjectively merging of two light pulses into one, at the second stage of measurement increase the duration of the pause between two light pulses until the subject determines the moment of subjective sensation of the separation of the two light pulses, at the third stage of measurement, reduce the pause between two light pulses until the subject determines the moment of subjective fusion of two light pulses into one, the time of the inertia of the visual system a person is taken equal to the value of the duration of the pause between two light pulses at the time of the subjective merger of two light pulses into one, op defined at the third stage of measurements, characterized in that the duration of the light pulses is 10 ms, at the second stage of measurements, increase the pause duration between two light pulses discretely with a given constant step of 0.4 ms, at the third stage of measurements reduce the pause duration between two light pulses with a given constant step of 0.1 ms.

The proposed method for determining the time of inertia of the human visual system is as follows.

Figure 1 presents the timing diagram of the presented light pulses to determine the time of inertia of the human visual system, where:

τ is the duration of the light pulse;

t _pnach is the initial pause duration between two light pulses;

T is a constant time interval between repeating two light pulses.

Figure 2 presents the time chart of the change in the duration of the pause t _p between two light pulses, figure 3 is a time chart of two light pulses of duration τ, separated by a pause and the visual sensations caused by them, where:

- figa - time diagram of two light pulses separated by a pause t _p causing a visual sensation of separation of pulses;

- figb - time diagram of the visual sensation of the two light pulses shown in figa;

- Fig.3c is a timing chart of two light pulses separated by a threshold pause t _pop , at which a subjective sensation of merging two light pulses into one is achieved;

- Fig. 3d is a timing diagram of the visual sensation of two light pulses shown in Fig. 3c;

- τ ₁ is the time of visual sensation - the time between the moment of exposure of light to the retina and the moment of occurrence of the corresponding visual sensation [9, 10] (Fig. 3d);

- τ ₂ is the recovery time is the time between the moment of termination of the effect of light on the retina and the moment the corresponding visual sensation disappears [9, 10] (Fig.3b).

The test subject is presented with a sequence of two light pulses of a given duration τ equal to 10 ms, separated by an initial pause t _pnach equal to 150 ms, repeated through a constant time interval T equal to 1.5 s (figure 1; figure 2, the time interval T ₀ - T ₁ ).

At the first stage of measurements, the duration of the initial pause t _first between two light pulses is reduced at a given constant speed of 20 ms / s (Fig. 2, the time interval T ₁ -T ₂ ), until the subject determines the subjectively merging of two light pulses into one (Fig. .2, point in time T ₂ ).

At the second measurement stage, the pause duration t _p between two light pulses is increased discretely with a given constant step of 0.4 ms (Fig. 2, the time interval T ₂ -T ₃ ) until the subject determines the moment of subjective sensation of the separation of the two light pulses (Fig. 2, point in time T ₃ ).

At the third measurement stage, the pause duration t _n between two light pulses is reduced discretely with a given constant step of 0.1 ms (Fig. 2, the time interval T ₃ -T ₄ ) until the subject determines the moment of subjective merging of the two light pulses into one (Fig. .2, point in time T ₄ ).

The duration of the pause t _ppo between two light pulses, determined at the third stage of measurements, is taken equal to the time of inertia of the human visual system.

Inertia of vision means the extension of visual sensation after turning off the stimulus [11]. During the action of the stimulus, the picture of the passage of the excitatory and inhibitory processes in the receptive fields of neurons is known [7]. As a result of these processes, receptive fields of neurons undergo 3 phases of rearrangement. During the first phase with a duration of the order of 10 ms, a spatio-temporal accumulation of signals and the formation of a zone of excitation of receptive fields occur. During the second phase, lasting from 50 to 60 ms, depending on the parameters of the stimulus, the process of narrowing the zone of summation of receptive fields proceeds. During the third phase of perestroika, the zones of summation of receptive fields expand and their functional disorganization occurs. Neural structures come to their original state and become ready for a new cycle of perception.

Since the first phase of the formation of receptive fields of neurons, that is, the on-response, ends after about 10 ms after the presentation of the light stimulus, the duration of the light pulses is taken to be 10 ms. With such a pulse duration, an off-response of neurons does not occur, the time of inertia of the visual system is determined in the absence of an off-response.

Upon presentation to the subject of two light pulses of duration τ> τ ₁ separated by a pause t _p > t _ppop ( _Fig. 3a), the processes of excitation and inhibition in the receptive fields of neurons caused by the first pulse will end, the neural structures will return to their original state and become ready for perception of the second impulse, therefore, the subject has a subjective sensation of separation of two light impulses (figb).

When reducing the duration of the pause t _n between two light pulses to a value of t _p = t _pp (Fig.3c), the processes of excitation and inhibition in the receptive fields of neurons caused by the first pulse do not have time to end, neural structures do not return to their original state and are not ready for perception of the second impulse, therefore, the subject has a feeling of subjective fusion of two light impulses into one (Fig. 3d).

Thus, the inventive method for determining the time of inertia of the human visual system has new properties that determine the receipt of a positive effect.

Example. Subject P., 21 years old, using a personal computer compatible with IBM PC that outputs light pulses through the LPT port to the indicator of the subject's remote control, showed a sequence of two light pulses of duration τ equal to 10 ms, separated by an initial pause t _pn equal to 150 ms, repeating through a constant time interval T equal to 1.5 s (figure 1; figure 2, the time interval T ₀ -T ₁ ).

In the process of measurement through the LPT port, the signals from the buttons "Continuous Decrease", "Increase by 0.4 ms", "Decrease by 0.1 ms" and "Measurement" were sent to the personal computer from the subject’s remote control. In the presence of a signal from the “Decrease Continuous” button, the computer continuously reduced the pause duration between two light pulses at a speed of 20 ms / s, when the signal from the “Increase by 0.4 ms” button received, it increased discretely by 0.4 ms, when the signal received from buttons “Decrease by 0.1 ms” discretely decreased by 0.1 ms, when the signal from the “Measurement” button was received, it fixed the pause duration t _support between two light pulses, displayed the value of the inertia time on the monitor screen, entered it into the archive and presented the initial by a sequence of two light pulses.

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

At the second stage of measurements, the test subject, giving a signal from the button "Increase by 0.4 ms" (figure 2, the time interval T ₂ -T ₃ ), determined the moment of subjective sensation of the separation of the two light pulses (figure 2, time T ₃ ) .

At the third stage of measurements, the test subject, giving a signal from the "Decrease by 0.1 ms" button (Fig. 2, time interval T ₃ -T ₄ ), determined the moment of subjective merging of two light pulses into one (Fig. 2, time moment T ₄ ), then applied a signal from the “Measurement” button (Fig. 2, time point T ₅ ).

The computer determined the duration of the pause time t _p = 56.2 ms between two light pulses, recorded by the subject at time T ₅ (Fig. 2), displayed the value of the inertia time on the monitor screen, entered it into the archive, and presented the initial sequence of two 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 inertia of the visual system of the test person were obtained, ms: 56.2; 56.4; 56.8; 56.7; 56.9; 57.2; 57.3; 57.8; 57.6; 58.2. The arithmetic average of the measured values of the inertia time of the visual system is 57.11 ms, the standard deviation is 0.13 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, 0.29 ms.

As a result of measuring the time of inertia of the visual system using the pulse duration τ = 10 ms, performed by the known method [6], the following values of the time of inertia of the visual system of the test person were obtained, ms: 58.9; 59.5; 59.4; 59.9; 59.7; 59.3; 60.2; 60.6; 61.2; 61.9. The arithmetic mean of the measured values of the inertia time of the visual system is 60.06 ms, the standard deviation is 0.19 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, 0.43 ms.

The decrease in the standard deviation, which characterizes the measurement error and is a criterion for the accuracy of measurements when performing measurements according to the proposed method compared with measurements made by the known method, was 32.27%.

To assess the reliability of reducing the measurement error, the time of inertia of the visual system was measured by the proposed and known methods in a group of 10 subjects, each of which performed a series of 10 measurements in each method. The decrease in measurement error when performing measurements according to the proposed method compared to measurements made by the known method, ranged from 24.82 to 42.85%.

Thus, the proposed method allows to determine the time of inertia of the human visual system in the absence of a signal generated by the off-system about the end of the light pulse, to reduce the error and increase the accuracy of measurements.

Sources of information

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Claims (1)

The method for determining the time of inertia of the human visual system, which consists in the fact that the test subject is presented with a sequence of two light pulses of a given duration, separated by a pause of 150 ms, repeated after a constant time interval of 1.5 s, and at the first stage of the measurements, the duration of the pause between two light pulses with a given constant speed of 20 ms / s, until the subject determines the subjectively merging of two light pulses into one, characterized in that the duration of total pulses is 10 ms, at the second measurement stage, the pause duration between two light pulses is increased discretely with a predetermined constant step of 0.4 ms, until the subject determines the moment of subjective sensation of the separation of two light pulses, at the third measurement stage, the pause duration between two light pulses is reduced discretely with a given constant step of 0.1 ms, until the subject determines the moment of subjective fusion of two light pulses into one, the time of inertia of the human visual system ayut to a value pause time between two light pulses when the subjective fusion of two optical pulses in one defined in the third phase measurements.

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