Cognitive function measurement system, measurement method, and measurement program

Abstract

To provide a cognitive function measurement system that can measure the cognitive function of subjects easily and accurately. [Solution] The cognitive function measurement system comprises: a presentation unit that presents a behavioral inhibition task to the subject; an input unit that causes the subject to input an answer to the task; a measurement unit that measures the reaction time from when the task is presented until the input of the answer is detected; a calculation unit that calculates a statistical value representing the variability of the reaction time obtained by performing the task a predetermined number of times; and a determination unit that determines the degree of the subject's cognitive function based on the statistical value.

Description

Technical Field

[0001] The present invention relates to a measurement system, a measurement method, and a measurement program for cognitive functions.

Background Art

[0002] Mild Cognitive Impairment (MCI) is a state "intermediate between a healthy state and dementia" ("MCI Handbook for a Healthy Mind and Body", National Center for Geriatrics and Gerontology, National Institute of Biomedical Innovation, Health and Nutrition, March 31, 2024, 2nd Edition, P.11, URL <https: / / www.mhlw.go.jp / content / 001272358.pdf>). It is said that if MCI is left untreated, it will progress to dementia, but there is a possibility of returning to a healthy state by taking appropriate preventive measures (ibid.). Therefore, it is important to detect MCI early and start countermeasures such as improving lifestyle habits and training at an early stage.

[0003] In medical institutions, as tests for MCI, MCI screening tests (blood tests), brain imaging tests such as head CT and MRI, and cognitive function tests are performed. Known cognitive function tests include the Hasegawa Dementia Scale, Mini-Cog, MoCA-J (Japanese version of MoCA), Trail Making Test A (TMT-A), Verbal Fluency Test (VFT), etc. [[ID=I7]]

[0004] Also, as technologies for examining cognitive functions, for example, Patent Documents 1 to 4 are known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] Many people find it inconvenient to visit a medical institution to undergo MCI testing. Therefore, there are concerns that MCI may be detected late. Furthermore, frequent medical examinations are difficult, often limited to once a year at best, or at least every few months. Consequently, even for patients diagnosed with MCI, it is difficult to track changes in the severity of their condition. Therefore, there is a need for technology that can easily measure cognitive function.

[0007] Furthermore, while conventional cognitive function tests often include many questions about memory and orientation, subjects with mild MCI may find the questions "too easy," leading to reluctance to take the test. Conversely, if the tasks and questions given to subjects in the test are too difficult, the burden on the subject will be greater, potentially causing them to hesitate to take the test again.

[0008] Furthermore, in tests that measure cognitive function based on the time taken to answer tasks or questions and the accuracy rate of those answers, a learning effect can occur where subjects improve their performance as they gain more experience with the test, becoming more familiar with the tasks and memorizing the questions. In such cases, it becomes difficult to accurately measure the subject's cognitive function.

[0009] The present invention has been made in view of the above, and aims to provide a cognitive function measurement system, measurement method, and measurement program that can measure the cognitive function of a subject in a simple and accurate manner. [Means for solving the problem]

[0010] To solve the above problems, a cognitive function measurement system according to one aspect of the present invention comprises: a presentation unit that presents a behavioral inhibition task to a subject; an input unit that causes the subject to input an answer to the task; a measurement unit that measures the reaction time from when the task is presented until the input of the answer is detected; a calculation unit that calculates a statistical value representing the variability of the reaction time obtained by performing the task a predetermined number of times; and a determination unit that determines the degree of the subject's cognitive function based on the statistical value.

[0011] In the cognitive function measurement system described above, the tasks may be the Go / No-Go task, the Stroop task, the Wisconsin Card Sorting Test, the Flanker task, the N-back task, the choice reaction time task, or the simple reaction time task.

[0012] In the cognitive function measurement system described above, the task is a Go / No-Go task, the measurement unit measures the reaction time as the time from when the Go stimulus is presented until the input to the input unit is detected, and the calculation unit may calculate a statistical value of the reaction time from when the Go stimulus is presented until the input to the input unit is detected.

[0013] In the cognitive function measurement system described above, the statistical value may be the coefficient of variation of reaction time.

[0014] In the cognitive function measurement system described above, the determination unit may classify the subject into a first group with a small degree of cognitive decline if the coefficient of variation is less than a threshold, and may classify the subject into a second group with a greater degree of cognitive decline than the first group if the coefficient of variation is equal to or greater than the threshold.

[0015] In the cognitive function measurement system described above, the display unit may be a display provided on a portable information terminal, and the input unit may be a touch panel provided on the display.

[0016] Another aspect of the present invention, a method for measuring cognitive function, includes presenting a subject with an action inhibition task, causing the subject to input an answer to the task, measuring the reaction time from when the task is presented until the input of the answer is detected, calculating a statistical value representing the variation in the reaction times obtained by executing the task a predetermined number of times, and a determination step of determining the degree of the subject's cognitive function based on the statistical value.

[0017] Another aspect of the present invention, a measurement program for cognitive function, causes a computer to execute presenting a subject with an action inhibition task, detecting that the subject has input an answer to the task, measuring the reaction time from when the task is presented until the input of the answer is detected, calculating a statistical value representing the variation in the reaction times obtained by executing the task a predetermined number of times, and a determination step of determining the degree of the subject's cognitive function based on the statistical value.

Advantages of the Invention

[0018] According to the present invention, it is possible to simply and accurately measure the cognitive function of a subject.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram showing the schematic configuration of a cognitive function measurement system according to an embodiment of the present invention. [Figure 2] It is a block diagram showing the schematic configuration of a cognitive function measurement system according to an embodiment of the present invention. [Figure 3] It is a flowchart showing the operation of a cognitive function measurement system according to an embodiment of the present invention. [Figure 4] It is a graph for explaining the processing of electroencephalogram data in a verification experiment. [Figure 5] It is a graph showing the result of a verification experiment (number of correct answers for Go stimuli). [Figure 6] It is a graph showing the result of a verification experiment (number of correct answers for No-Go stimuli). [Figure 7] This is a graph showing the results of the verification experiment (average reaction time). [Figure 8] This is a graph showing the results of the verification experiment (reaction time variation). [Figure 9] This is a graph showing the results of the verification experiment (ERP for No-Go stimuli). [Figure 10] This is a graph showing the results of the verification experiment (correlation analysis). [Figure 11] This is a graph showing the results of the verification experiment (correlation analysis). [Figure 12] This is a graph showing the results of the verification experiment (ROC analysis). [Figure 13] This is a graph showing the results of the verification experiment (ROC analysis). [Figure 14] This is a graph showing the results of the verification experiment (ROC analysis).

Mode for Carrying Out the Invention

[0020] Hereinafter, a cognitive function measurement system, a measurement method, and a measurement program according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited by these embodiments. Also, in the description of each drawing, the same parts are denoted by the same reference numerals.

[0021] The drawings referred to in the following description only schematically show the shape, size, and positional relationship to the extent that the content of the present invention can be understood. That is, the present invention is not limited only to the shape, size, and positional relationship illustrated in each drawing. Also, there may be parts where the dimensional relationships and ratios between the drawings are different from each other.

[0022] (Configuration of the Measurement System) Figure 1 is a schematic diagram showing the general configuration of a cognitive function measurement system according to an embodiment of the present invention. The cognitive function measurement system 1 according to this embodiment (hereinafter simply referred to as the measurement system) is a system for measuring the cognitive function of a subject 2, and comprises a display unit 14 as a presentation unit that presents a behavioral inhibition task to the subject, an input unit 15 for the subject to input their answers to the behavioral inhibition task, and an information processing unit 10 that executes a process to measure cognitive function based on the information output from the input unit 15.

[0023] Here, behavioral inhibition tasks refer to methods for evaluating the behavioral inhibition function of the frontal lobe. Specific examples of behavioral inhibition tasks include the Go / No-Go task, the Stroop task, the Wisconsin Card Sorting Test, the Flanker task, the N-back task, the choice reaction time task, and the simple reaction time task.

[0024] A Go / No-Go task is a task in which subject 2 is required to respond quickly when given a Go (response) stimulus, and to suppress their response when given a No-Go (inhibition) stimulus. For example, subject 2 is given a task in which they must press a switch when one of two letters is displayed (Go stimulus), but must not press the switch when the other letter is displayed (No-Go stimulus).

[0025] The Stroop task is a task that requires participants to process a contradiction between the meaning of a word and a color. Specifically, for example, when the word "red" is presented in blue, participant 2 is given the task of identifying the color (blue) rather than the meaning of the word (red).

[0026] The Wisconsin Card Sorting Test is a task that measures the ability to adapt to rule changes. Specifically, for example, participant 2 is presented with cards of different colors, shapes, and numbers, and is given feedback when participant 2 classifies them according to a rule (e.g., color). However, the rule is changed midway through (e.g., shape), and participant 2 is given the task of suppressing the previous rule (color) and adapting to the new rule (shape).

[0027] The Flanker task is a task in which a subject responds while suppressing interfering stimuli placed around a target stimulus. Specifically, for example, when subject 2 is presented with a sequence of arrows such as "→→→→→", they are asked to respond based on the central arrow (target stimulus). However, if the arrows on both sides (interfering stimuli) point in different directions, such as "←←→←←", subject 2 is given the task of suppressing the influence of the surrounding arrows and responding correctly in the direction of the central arrow.

[0028] The N-back task is a task in which a participant compares a current stimulus with a stimulus that was presented at a certain interval while keeping the previous stimulus in mind. Specifically, for example, if participant 2 is presented with a sequence of letters such as "A→B→C→A→C", in the 2-back task, they must determine whether the current stimulus matches the stimulus two stimuli prior. In this case, the fourth letter "A" is different from the "B" two stimuli prior, so the answer must be "mismatched," and the fifth letter "C" matches the "C" two stimuli prior, so the answer must be "matched." Participant 2 is given the task of processing new information while maintaining past information.

[0029] A selection reaction time task is a task in which a person must select an appropriate response to a presented stimulus and respond quickly. Specifically, for example, subject 2 is presented with a red light and a blue light, and is instructed to press a button with their right hand when the red light is on, and with their left hand when the blue light is on. Subject 2 is given the task of identifying the type of stimulus, selecting the appropriate response to it, and executing it quickly.

[0030] A simple reaction time task is a task in which a subject must react as quickly as possible when a stimulus is presented. Specifically, for example, subject 2 is instructed to press a button regardless of the type of stimulus when a light on the screen lights up. In this task, subject 2 is given the task of recognizing the appearance of the stimulus and reacting as quickly as possible.

[0031] Figure 2 is a block diagram showing the schematic configuration of measurement system 1. The display unit 14 is, for example, a liquid crystal display or an organic EL display, and displays the behavioral suppression task on the screen under the control of the information processing unit 10.

[0032] The input unit 15 consists of input devices such as push-button switches, keyboards, mice, and touch panels on the display, which input signals corresponding to operations performed from the outside to the information processing unit 10.

[0033] The information processing unit 10 can be configured using a general-purpose computer such as a personal computer (PC), notebook PC, tablet terminal, or smartphone. As shown in Figure 2, the information processing unit 10 includes an external interface 11, a storage unit 12, and a processor 13.

[0034] The external interface 11 is an interface that connects the information processing unit 10 to external devices (e.g., display unit 14, input unit 15) or communication lines (e.g., internet line), and transmits and receives information between the external devices and communication lines.

[0035] The storage unit 12 can be configured using, for example, a computer-readable storage medium such as semiconductor memory like ROM or RAM, or a hard disk. The storage unit 12 includes a program storage unit 121, a task storage unit 122, and a measurement data storage unit 123.

[0036] The program storage unit 121 stores operating system programs, driver programs, application programs that perform various functions, and various parameters used during the execution of these programs. Specifically, the program storage unit 121 stores measurement programs for executing processes to measure the cognitive function of subject 2 based on the reaction time from when a task is presented until a response is detected, as well as thresholds used during the execution of the measurement programs.

[0037] The task storage unit 122 stores the behavioral inhibition tasks presented during the execution of the measurement program. For example, if a Go / No-Go task is used as the behavioral inhibition task, the image data of the alphabet displayed on the display unit 14 is stored in the task storage unit 122.

[0038] The measurement data storage unit 123 stores the data acquired through measurement. Specifically, the reaction time from the presentation of the task until the input of the response is detected, statistical values ​​of these reaction times, and the results of cognitive function assessments based on these statistical values ​​are stored in the measurement data storage unit 123. The measurement data storage unit 123 may also store the assessment results, the statistical values ​​used in the assessment, or scores obtained by converting the statistical values ​​using a predetermined formula, in chronological order for each subject.

[0039] The processor 13 is configured, for example, using a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit), and by reading various programs stored in the program storage unit 121, it comprehensively controls each part of the measurement system 1 and performs various calculations for measuring the cognitive function of the subject 2. The functional units realized by the processor 13 include a task presentation processing unit 131, a measurement unit 132, a calculation unit 133, and a judgment unit 134.

[0040] The task presentation processing unit 131 performs the processing of presenting the behavioral inhibition task to the display unit 14. For example, when a Go / No-Go task is performed, the task presentation processing unit 131 randomly displays images representing characters as Go stimuli and images representing characters as No-Go stimuli on the display unit 14 a predetermined number of times.

[0041] The measurement unit 132 measures the reaction time from when a behavioral inhibition task is presented until the input of a response is detected. For example, when a Go / No-Go task is performed, the measurement unit 132 may measure the reaction time from when the Go stimulus or No-Go stimulus is displayed on the screen until the input to the input unit 15 is detected, or it may measure the reaction time only when the Go stimulus is displayed.

[0042] The calculation unit 133 calculates a statistical value representing the variability of reaction times obtained by performing the behavioral inhibition task a predetermined number of times. Specifically, it can use variance, standard deviation, coefficient of variation (relative standard deviation), etc.

[0043] The determination unit 134 determines the degree of cognitive function of subject 2 based on the statistical values ​​calculated by the calculation unit 133. Specifically, it classifies the degree of cognitive function of subject 2 into several groups by comparing the statistical values ​​with pre-acquired thresholds.

[0044] Although the measurement system 1 shown in Figure 1 has a configuration in which the display unit 14 and input unit 15 are externally attached to the information processing unit 10, the display unit 14 and input unit 15 may also be built into the information processing unit 10. For example, the display unit 14 may be a display provided on a portable information terminal such as a tablet or smartphone, and the input unit 15 may be a touch panel provided on this display.

[0045] (Measurement system operation) Figure 3 is a flowchart showing the operation of cognitive function measurement system 1. The following section describes the case where the Go / No-Go task is implemented as a behavioral inhibition task.

[0046] When performing the Go / No-Go task, the display unit 14 is placed in front of the subject 2, and the subject 2 waits in a position where they can operate the input unit 15. The subject 2 is given the task of performing an input operation on the input unit 15 when the word "Go" stimulus is displayed, and refraining from performing an input operation on the input unit 15 when the word "No-Go" stimulus is displayed.

[0047] When cognitive function measurement begins, the task presentation processing unit 131 displays the task on the display unit 14 for a predetermined time (for example, several hundred ms) (step S11). Specifically, an image showing the words "Go stimulus" or "No-Go stimulus" is displayed on the screen.

[0048] Next, the measurement unit 132 measures the time until it detects input of a response to the task (step S12). For the response, when a Go stimulus is displayed, it is considered a correct answer if an input operation is performed on the input unit 15, and an incorrect answer if no input operation is performed within a predetermined time. Conversely, when a No-Go stimulus is displayed, it is considered a correct answer if no input operation is performed on the input unit 15 within a predetermined time, and an incorrect answer if an input operation is performed. The measurement unit 132 measures the time from when the stimulus is displayed until an input operation is performed (until an operation on the input unit 15 is detected) as the reaction time.

[0049] These steps S11-S12 are repeated until the task is presented a predetermined number of times. The number of Go stimuli and No-Go stimuli is predetermined, and the order in which the Go stimuli and No-Go stimuli are presented is randomly determined within the specified number of times.

[0050] After the task has been presented a predetermined number of times, the calculation unit 133 calculates a statistical value of the reaction time (step S13). In the case of a Go / No-Go task, the variability of the reaction time when the Go stimulus is displayed is calculated. Specifically, the coefficient of variation CV calculated by the following equation (1) can be used as the statistical value. In equation (1), σ represents the population standard deviation and μ represents the population mean. CV = σ / μ …(1)

[0051] This coefficient of variation (CV) represents the intra-individual variability in reaction time (IIV-RT) for each individual subject. Here, the reaction time obtained when performing a certain task is distributed around the mean value. The magnitude of this reaction time variability varies from person to person. In this embodiment, the reaction time variability for each individual subject is calculated.

[0052] Next, the determination unit 134 determines the cognitive function of subject 2 by comparing the statistical value of reaction time with a threshold (step S14). Here, when subject 2 is given a behavioral inhibition task, there is a positive correlation between the variability of reaction time and the degree of cognitive decline; the greater the variability, the greater the decline in cognitive function. Therefore, by comparing the statistical value of reaction time with a preset threshold, the degree of cognitive function of subject 2 can be classified.

[0053] For example, the determination unit 134 may classify the degree of cognitive function into two groups by comparing the coefficient of variation with a threshold. That is, if the coefficient of variation is less than the threshold Th, subject 2 can be classified into a first group with a small degree of cognitive decline, and if the coefficient of variation is equal to or greater than the threshold Th, subject 2 can be classified into a second group with a greater degree of cognitive decline than the first group. For example, Th = 25.37% can be used as the threshold. Of course, multiple thresholds may be prepared to classify the degree of cognitive decline into three or more groups.

[0054] Next, the determination unit 134 displays the determination result (the result of classifying into two groups) on the display unit 14 and stores it in the storage unit 12 (step S15). At this time, the coefficient of variation of the reaction time, or a value obtained by converting the coefficient of variation using a predetermined formula, may also be stored in the storage unit 12 as a score. After that, the operation of the measurement system ends.

[0055] Here, the judgment unit 134 may store the judgment results and scores in chronological order in the storage unit 12 for each subject. In this case, the judgment results and scores stored in the storage unit 12 can be read out as needed and displayed in chronological order on the display unit 14.

[0056] As described above, this embodiment makes it possible to measure the cognitive function of a subject in a simple and accurate manner.

[0057] In detail, in this embodiment, measurement is performed by giving the subject a behavioral inhibition task. In this case, the subject can input their answers with only simple input operations (for example, only pressing a button or only tapping on a touch panel), making the measurement easy to undergo. Furthermore, if the measurement system 1 is configured using a portable information terminal such as a tablet or smartphone, the measurement can be performed anywhere, eliminating the need for the subject to go to a medical institution or similar facility. In addition, with behavioral inhibition tasks, the subject will not feel resistance to questions that are too easy, nor will they feel burdened by tasks that are too difficult. Therefore, it becomes possible to have the subject undergo the measurement repeatedly.

[0058] Furthermore, according to this embodiment, the degree of cognitive decline can be measured with high accuracy by using the subject's reaction time variation. Moreover, when using reaction time variation, unlike when measuring based on reaction time length or accuracy rate, there is no learning effect due to measurement experience. Therefore, according to this embodiment, it is possible to maintain measurement accuracy even when measurements are performed regularly or frequently.

[0059] By configuring a system that can measure cognitive function simply and with high accuracy, it becomes easier to detect cognitive decline in subjects at an early stage. This makes it possible to encourage subjects to take behavioral changes such as training to suppress cognitive decline or restore cognitive function, or to improve their lifestyle. Furthermore, by having subjects undergo measurements regularly or frequently, the effects of such behavioral changes can be made apparent to the subjects, providing them with the motivation to continue the changes. For example, the results and scores obtained by regularly measuring cognitive function with the measurement system 1 can be stored in the memory unit 12, and the effects of behavioral changes can be visualized by allowing subjects to check the time-series data of the results and scores at any time.

[0060] In the above embodiment, the Go / No-Go task was used as an example of a behavioral inhibition task, but other tasks may also be used. Furthermore, while the above embodiment mentions a display unit as a means of presenting a task for behavioral inhibition, other means may be used depending on the type of task. For example, when presenting a task via voice, a speaker or headset can be used as the means of presenting the task.

[0061] (Verification experiment) An experiment was conducted to verify the measurement accuracy of the cognitive function measurement method according to the embodiment of the present invention. 1. Subject The study included 46 elderly individuals (average age 72.1 ± 3.3 years) and 34 healthy adults (average age 21.3 ± 1.2 years). The elderly participants underwent the MoCA-J test. Those scoring 26 points or higher were classified as having normal cognitive function (hereinafter also referred to as the "normal cognitive function group"), while those scoring 25 points or lower were classified as having impaired cognitive function (hereinafter also referred to as the "impaired cognitive function group"). There were 31 elderly individuals in the normal cognitive function group and 15 in the impaired cognitive function group.

[0062] The selection criteria for the subjects were as follows: • Independent in basic activities of daily living (ADL) and instrumental activities of daily living (IADL). • They have not been diagnosed with dementia or mild cognitive impairment (MCI). • There is no subjective decline in cognitive function. • Vision is normal or corrected to 0.7 or higher.

[0063] 2. Experimental Environment A 22.5-inch desktop monitor (manufactured by EIZO Corporation) was placed on the desk, and a chair was positioned in front of the desk. The subject sat approximately 60 cm away from the screen and was given a push-button switch. Electrodes for electroencephalography (EEG) were attached to the subject's head, and electroencephalography (EEG) was measured during the Go / No-Go task. A Polymate Mini AP108, manufactured by Miyuki Giken Co., Ltd., was used as the electroencephalograph.

[0064] 3. Experimental Method For the Go / No-Go task, a white letter "O" (alphabet) or "S" in 300-point font was displayed on a monitor as a visual stimulus against a black background. The stimulus display time was set to 500ms, and the interval between stimulus displays was also set to 500ms, with only the black background displayed during the intervals between displays.

[0065] Each subject was given a total of 400 visual stimuli, of which 300 (75%) were Go stimuli and 100 (25%) were No-Go stimuli. In addition, half of the subjects were given the letter "O" as a Go stimulus and the letter "S" as a No-Go stimulus to consider the influence of the letters, while the other half were given the letter "S" as a Go stimulus and the letter "O" as a No-Go stimulus.

[0066] Then, the reaction time from the display of the stimulus to the input of the response was measured, and the reaction time variation (IIV-RT) for the Go stimulus was calculated using the following equation (2). IIV-RT(%) = (Standard deviation of reaction time / Mean reaction time) × 100 …(2)

[0067] In addition, electroencephalograms (EEGs) were measured simultaneously with the Go / No-Go task to measure event-related potentials (ERPs). Here, ERPs are EEG components that record the brain's electrical activity in response to a specific stimulus or task (Go / No-Go task). Figure 4 is a graph illustrating the processing of EEG waveform data. As illustrated in Figure 4, a single waveform can be obtained by averaging the raw EEG waveforms (100 waveforms) when a No-Go stimulus is applied, using the trigger (e.g., the time the task is presented) as the reference point. From this waveform, characteristic components called N2 and P3 can be observed. The N2 component is a negative component that appears around 200 ms from the presentation of the task and is related to cognitive conflict. The P3 component is a positive component that appears around 300 ms from the presentation of the task and is related to stimulus evaluation, attention, and inhibition.

[0068] 4. Experimental Results Figures 5 to 14 are graphs showing the results of the verification experiment. As shown in Figure 5, the number of correct responses to the Go stimulus was generally concentrated around 300 in the healthy adult group and the cognitively impaired group, while the average was 296 in the cognitively impaired group, and there was considerable variability among subjects. Therefore, it can be said that there are significant differences between the healthy adult group and the cognitively impaired group, and between the cognitively impaired group and the cognitively impaired group.

[0069] On the other hand, as shown in Figure 6, the average number of correct responses to No-Go stimuli was 86 in the healthy adult group and the cognitively normal group, and 79 in the cognitively impaired group, with no significant difference observed.

[0070] As shown in Figure 7, the average reaction time was 270 ms for the healthy adult group, 331 ms for the cognitively normal group, and 373 ms for the cognitively impaired group. The healthy adult group was significantly faster than the two elderly groups. On the other hand, no significant difference was observed between the two elderly groups.

[0071] As shown in Figure 8, the average reaction time variability was 19% for the healthy adult group and 20% for the cognitively normal group, with no significant difference observed between the two groups. In contrast, the average reaction time variability in the cognitively impaired group was 27%, showing a significant difference not only between the healthy adult group but also between the cognitively normal group and the cognitively impaired group.

[0072] Figure 9 shows the ERP waveforms for No-Go stimulation, with the averaged values ​​calculated for each group of subjects. In each waveform, the negative component appearing around 200 ms is the N2 component, and the positive component appearing around 300 ms is the P3 component. Here, the time from the start of stimulation until each component clearly appears (changes to clearly negative or positive) is called the latency, and the magnitude of this component is called the amplitude.

[0073] Table 1 shows the latency of the N2 component in response to No-Go stimulation. Table 2 shows the amplitude. Below, FCz, Cz, CPz, and Pz indicate the positions of the electrodes used for electroencephalography. Of these, FCz (Fronto-Central Midline) is located on the midline of the central frontal region. Cz (Central Midline) is located on the midline of the central region. CPz (Centro-Parietal Midline) is located on the midline of the central parietal region. Pz (Parietal Midline) is located on the midline of the central parietal region. Cohen's d was used as the effect size (ES).

[0074] [Table 1]

[0075] [Table 2]

[0076] As shown in Table 1, the latency of the N2 component was 245 ms for the healthy adult group (HA) and 249 ms for the elderly cognitively impaired group (NC) at site FCz, with no significant difference observed between the two groups (see HA vs NC). In contrast, the latency for the elderly cognitively impaired group (CI) at site FCz was 282 ms, showing a significant difference from the healthy adult group (see HA vs CI). Significant differences were also observed between the healthy adult group and the cognitively impaired group for the other sites Cz, CPz, and Pz, with the healthy adult group having a significantly shorter latency (i.e., faster). Furthermore, significant differences were observed between the cognitively impaired group and the cognitively impaired group at sites FCz and Cz, with the cognitively impaired group having a significantly shorter latency (see NC vs NC).

[0077] As shown in Table 2, regarding the amplitude of the N2 component, at site FCz, the healthy adult group had an amplitude of -8.0, while the cognitively normal group had an amplitude of -1.7, with the healthy adult group showing a significantly larger amplitude. Similarly, at sites Cz and CPz, the healthy adult group showed a significantly larger amplitude compared to the cognitively normal group (see HA vs NC). Furthermore, the amplitude of the cognitively impaired group at site FCz was -2.2, showing a significant difference compared to the healthy adult group. Similarly, at site Cz, the healthy adult group showed a significantly larger amplitude compared to the cognitively impaired group (see HA vs CI). On the other hand, no significant difference was observed between the two groups of elderly individuals (NC, CI) (see NC vs CI).

[0078] Table 3 shows the latency of the P3 component in response to the No-Go stimulus. Table 4 shows the amplitude of the same component. [Table 3]

[0079] [Table 4]

[0080] As shown in Table 3, the latency of the P3 component at site FCz was 359.7 ms for the healthy adult group (HA) and 413 ms for the elderly group with normal cognitive function (NC), showing a significant difference between the two groups (see HA vs NC). Significant differences were also observed between these two groups for other sites Cz, CPz, and Pz, with the healthy adult group having a significantly shorter latency. Furthermore, the latency for the cognitively impaired group (CI) at site FCz was 430 ms, showing a significant difference compared to the healthy adult group (see HA vs CI). Similar significant differences were observed for other sites Cz, CPz, and Pz, with the healthy adult group having a significantly shorter latency compared to the cognitively impaired group. On the other hand, no significant differences were observed between the two elderly groups (see NC vs CI).

[0081] As shown in Table 4, the amplitude of the P3 component at site FCz was 18.4 for the healthy adult group (HA) and 12.3 for the elderly group with normal cognitive function (NC), showing a significant difference between the two groups (see HA vs NC). Significant differences were also observed between these two groups at other sites Cz, CPz, and Pz, with the healthy adult group showing significantly larger amplitudes. Furthermore, the amplitude of the cognitive impairment group (CI) was 8.3, showing a significant difference compared to the healthy adult group (see HA vs CI). Significant differences were also observed at other sites Cz, CPz, and Pz, with the healthy adult group showing significantly larger amplitudes compared to the cognitive impairment group. On the other hand, no significant differences were observed between the two elderly groups (see NC vs CI).

[0082] Figure 10 is a graph showing the correlation analysis results between scores on the neuropsychological assessment (MoCA-J) for the elderly and reaction time variability (IIV-RT). In Figure 10, the horizontal axis represents the MoCA-J score, and the vertical axis represents the reaction time variability (%). The correlation coefficient between the MoCA-J score and reaction time variability was -0.531, indicating that a lower MoCA-J score is associated with greater reaction time variability.

[0083] Figure 11 is a graph showing the correlation analysis results between MoCA-J scores and event-related potentials (ERPs) in elderly individuals. In Figure 11, the horizontal axis represents the MoCA-J score, and the vertical axis represents the latency of the N2 component to No-Go stimulation at site FCz. The correlation coefficient between the MoCA-J score and the latency of the N2 component was -0.425, indicating that a lower MoCA-J score is associated with a longer (i.e., slower) latency. Furthermore, Table 5 shows the correlation analysis results between the MoCA-J score and the latency at sites FCz, Cz, and Pz.

[0084] [Table 5]

[0085] Table 6 shows the correlation analysis results between TMT-A scores (a neuropsychological test) and the latencies of IIV-RT and N2 components. Table 7 shows the correlation analysis results between VFT scores (another neuropsychological test) and the latencies of IIV-RT and N2 components.

[0086] [Table 6]

[0087] [Table 7]

[0088] Figure 12 is a graph showing the results of a ROC analysis regarding the classification of cognitive function using reaction time variability (IIV-RT). As shown in Figure 12, the area under the curve (AUC) is 0.9 or higher, indicating that subjects with normal cognitive function and subjects showing cognitive decline can be distinguished with high accuracy. The cutoff value at this point was 25.37%, suggesting that cognitive decline may be suspected when reaction time variability exceeds the cutoff value.

[0089] Figures 13 and 14 are graphs showing the results of ROC analysis on the classification of cognitive function using the latency of the N2 component in response to No-Go stimuli. Figure 13 shows the results for site FCz, and Figure 14 shows the results for site Cz. As shown in Figures 13 and 14, the AUC was 0.7 or higher for both site FCz and Cz, indicating moderate cognitive discriminative ability. The cutoff values ​​were 251 ms for site FCz and 261 ms for site Cz, suggesting that cognitive decline may be suspected when the latency exceeds these cutoff values.

[0090] The experimental results above show that the degree of cognitive decline in subjects can be classified using reaction time variability and ERP. In particular, reaction time variability allowed for highly accurate classification of the degree of cognitive decline.

[0091] Even when using behavioral inhibition tasks other than the Go / No-Go task, similar to the experiment described above, a behavioral inhibition task can be given to a group of subjects classified by cognitive function tests such as the MoCA-J test, statistical values ​​representing the variability of reaction times (e.g., reaction time variability) can be calculated, and a cutoff value can be determined by performing ROC analysis. The cutoff value thus obtained can be used as a threshold for determining the degree of cognitive function of the subjects in the measurement system according to the above embodiment.

[0092] The present invention is not limited to the embodiments described above, and can be implemented in various other forms without departing from the spirit of the invention. For example, it may be formed by excluding some of the components shown in the above embodiments, or by appropriately combining other components. [Explanation of Symbols]

[0093] 1...Measurement system, 2...Subject, 10...Information processing unit, 11...External interface, 12...Storage unit, 13...Processor, 14...Display unit, 15...Input unit, 121...Program storage unit, 122...Task storage unit, 123...Measurement data storage unit, 131...Task presentation processing unit, 132...Measurement unit, 133...Calculation unit, 134...Determination unit

Claims

1. A presentation unit that presents the subject with a challenge to inhibit behavior, An input unit for allowing the subject to input their answer to the aforementioned task, A measurement unit measures the reaction time from the presentation of the aforementioned problem until the input of the answer is detected, A calculation unit that calculates a statistical value representing the variability of reaction times obtained by performing the aforementioned task a predetermined number of times, A determination unit that determines the degree of the subject's cognitive function based on the aforementioned statistical values, A cognitive function measurement system equipped with the following features.

2. The cognitive function measurement system according to claim 1, wherein the task is a Go / No-Go task, a Stroop task, a Wisconsin Card Sorting Test, a Flanker task, an N-back task, a choice reaction time task, or a simple reaction time task.

3. The aforementioned issue is a Go / No-Go issue, The measurement unit measures the reaction time as the time from when the Go stimulus is presented until the input to the input unit is detected. The calculation unit calculates a statistical value of the reaction time from the time the Go stimulus is presented until the input to the input unit is detected. The cognitive function measurement system according to claim 1.

4. The cognitive function measurement system according to any one of claims 1 to 3, wherein the aforementioned statistical value is the coefficient of variation of reaction time.

5. The determination unit, If the coefficient of variation is below the threshold, the subjects are classified into a first group with a small degree of cognitive decline. If the coefficient of variation is greater than or equal to the threshold, the subject is classified into a second group, which has a greater degree of cognitive decline than the first group. The cognitive function measurement system according to claim 4.

6. The aforementioned display unit is a display provided by a mobile information terminal. The input unit is a touch panel provided on the display. The cognitive function measurement system according to claim 1.

7. Steps include presenting the subject with a challenge to inhibit behavior, The steps include having the subject input their answers to the aforementioned task, The steps include measuring the reaction time from the presentation of the aforementioned task until the input of the response is detected, The steps include: calculating a statistical value representing the variability of reaction times obtained by performing the aforementioned task a predetermined number of times; A determination step is to determine the degree of the subject's cognitive function based on the aforementioned statistical values, A method for measuring cognitive function, including the measurement of cognitive function.

8. Steps include presenting the subject with a challenge to inhibit behavior, A step to detect that the answer to the aforementioned task has been entered by the subject, The steps include measuring the reaction time from the presentation of the aforementioned task until the input of the response is detected, The steps include: calculating a statistical value representing the variability of reaction times obtained by performing the aforementioned task a predetermined number of times; A determination step is to determine the degree of the subject's cognitive function based on the aforementioned statistical values, A program that causes a computer to execute something.

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