Movement cortex excitability evaluation method based on threshold tracking magnetic stimulation

Abstract

The invention discloses a motor cortex excitability evaluation method based on threshold tracking magnetic stimulation, and relates to the technical field of biomedical engineering. The motor cortex excitability assessment method based on threshold tracking magnetic stimulation comprises the following steps: performing electrical stimulation on median nerves of a wrist of a subject, recording on an abductor politics brevis (APB), recording a stimuli-response curve, determining a stimuli-response (SR) curve of cortex stimulation by increasing the magnetic stimulation intensity to the following level, and determining the stimuli-response (SR) curve of cortex stimulation according to the stimuli-response (SR) curve. And calculating statistical parameters of the average value and the standard deviation of the excitability threshold values, and judging the dynamic trend of cortical excitability. According to the method, the stimulation-reaction curve of cortex stimulation is determined by improving the magnetic stimulation intensity to the following level, the central movement conduction time is calculated through the F-wave method based on the stimulation-reaction curve, initial stimulation and threshold determination are completed, subsequent threshold tracking is carried out on the technology, and the accuracy and the reliability of the system are improved. And an efficient and accurate brain motor cortex function detection means is provided for diagnosis of nervous system diseases.

Description

Technical Field

[0001] The invention relates to the technical field of biomedical engineering, and in particular to a method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation. Background Art

[0002] Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease of the central nervous system. At the pathophysiological level, ALS is a multi-stage process. There is increasing evidence that ALS originates from the motor cortex, and the hyperexcitability of the cortex mediates the degeneration of lower motor neurons through the synaptic glutamatergic excitotoxic mechanism. Increased excitability of the motor cortex is an early and intrinsic feature of sporadic and familial ALS.

[0003] Transcranial magnetic stimulation (TMS) is a neuroelectrophysiological technique that provides a non-invasive and painless method for evaluating cortical function. As a non-invasive detection method, TMS technology has high temporal and spatial resolution. However, conventional TMS technology often cannot track excitability changes in real time, dynamically and accurately when detecting motor cortical excitability. It is limited by the amplitude fluctuation of motor evoked potentials and is difficult to meet the clinical and scientific research needs for fine evaluation of brain motor cortical function. Threshold tracking TMS technology came into being, which can easily determine whether ALS patients have increased cortical excitability. Threshold tracking TMS technology is used to detect cortical excitability, and high cortical excitability in ALS patients has been established as a powerful diagnostic biomarker. Therefore, threshold tracking TMS technology helps to diagnose and differentially diagnose ALS and distinguish it from ALS-like syndromes. TMS technology can be used to evaluate cortical excitability. It is a non-invasive neuroelectrophysiological tool that reflects the function of cortical output cells and intracortical neuronal networks in the primary motor cortex. Initially, the constant stimulation technique was used to measure cortical excitability by giving a subthreshold conditioned stimulus followed by multiple conditioned test stimuli at an interstimulus interval (ISI) of 1–5 ms to produce multiple motor evoked potentials (MEPs) and recording the reduction in the amplitude of each MEP. This parameter, called short-interval intracortical inhibition (SICI), may be a biomarker of intermediate inhibitory cortical neurons generated through GABA-A receptor circuits. The most commonly used parameter is short-interval intracortical inhibition (SICI), and there is another parameter called long-interval intracortical inhibition (LICI), which occurs at an interstimulus interval of 50–300 ms and peaks at 150 ms.In view of the fact that the constant stimulation TMS technology may be limited by the change of the motor evoked potential amplitude, there is currently a "paired pulse TMS mode", that is, a subthreshold conditioned stimulus is first given, and then a conditioned test stimulus is given to produce a motor evoked potential, and the process is repeated multiple times to gradually adjust the best effect. The specific method is that one of the fixed motor evoked potential amplitudes is tracked by a test stimulus, so that the SICI will be predicted by a larger conditioned test stimulus intensity to produce and maintain the target motor evoked potential response. Compared with the constant stimulation technology, the threshold tracking TMS technology improves reproducibility and shortens the acquisition time. This technology reveals the great prospect of using this technology for the study of motor cortex circuit function. Therefore, the present application provides a further motor cortex excitability assessment method based on threshold tracking magnetic stimulation. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation, which solves the problems raised in the above-mentioned background technology.

[0005] To achieve the above objectives, the present invention is implemented by the following technical scheme: a method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation, the method comprising the following specific steps: S1: Assess peripheral nerves; electrically stimulate the median nerve at the wrist of the subject, record the resulting compound muscle action potential through surface electrodes, and measure the peak-to-peak amplitude and onset latency of the compound muscle action potential, and measure the peak-to-peak amplitude and onset latency of the compound muscle action potential for the electrical stimulation, record the stimulus-response curve, calculate the time constant of intensity-duration, record the F wave, and measure its onset latency; S2: Determination of initial stimulation and threshold; applying transcranial magnetic stimulation to the motor cortex based on an 8-shaped coil, synchronously collecting muscle response signals through an electromyographic acquisition device, gradually adjusting the stimulation intensity, and determining the stimulus-response curve of cortical stimulation by increasing the intensity of magnetic stimulation to the following levels, applying stimulation three times at each stimulation intensity level, and recording the maximum motor evoked potential amplitude and motor evoked potential onset latency, and calculating the central motor conduction time according to the F-wave method; in the traditional double-pulse technique, the intensity of the conditioned stimulus and the test stimulus remains constant, and the change in the amplitude of the motor evoked potential is measured, while in the threshold tracking TMS output is fixed, and the change in the test stimulus intensity required to produce the target response after the subthreshold or suprathreshold conditioned stimulus is measured. The threshold tracking strategy adopted is based on the previous observation that the stimulus-response relationship is exponential.

[0006] S3: Threshold tracking; repeat the S2 operation, and increase the stimulation interval in sequence, the applied stimulation is delivered in sequence by the three channels, and after the stimulation produces two consecutive evoked potential and motor evoked potential responses, the threshold tracking result is considered acceptable, and then repeat the S2 operation, the stimulation interval is increased in sequence again, and the stimulation is delivered in sequence by the two channels; S4: Data analysis and result output; Based on the data obtained in S1, S2 and S3, the statistical parameters of the mean and standard deviation of the excitability threshold are calculated to evaluate the stability of the excitability of the motor cortex of the brain, and the dynamic trend of the cortical excitability is determined by comparing the threshold changes in different time periods.

[0007] A further improvement of the technical solution of the present invention is that S1 further includes the following preparatory steps: S1-1: Pre-preparation: After the subject is in a quiet and comfortable state, fix the subject's head position, aim the transcranial magnetic stimulation coil at the target area of ​​the motor cortex of the brain, and stick electromyographic electrodes on the target muscle groups in the target area, and connect the electromyographic acquisition device.

[0008] A further improvement of the technical solution of the present invention is that the specific stimulation time limit for electrically stimulating the median nerve at the wrist in S1 is: 0.2 milliseconds and 1 millisecond; The number of F waves recorded in S1 is specifically 10.

[0009] A further improvement of the technical solution of the present invention is that the 8-shaped coil in S2 applies transcranial magnetic stimulation to the motor cortex including the following specific settings: The size of the figure-8 coil is 90 mm; The direction of the figure-8 coil is set to induce the current to flow in the back-to-front direction; The figure-of-eight coil was initially placed at the center of the top of the head and then moved in the anterior-posterior and lateral-lateral directions to find the optimal position that evoked the greatest amplitude response from the APB muscle.

[0010] A further improvement of the technical solution of the present invention is that the transcranial magnetic stimulation applied to the motor cortex based on the figure-8 coil in S2 is a single-pulse stimulation, and the stimulation-response curve in S2 specifically includes 60%, 80%, 90%, 100%, 110%, 120%, 130%, 140% and 150% of the resting motor threshold.

[0011] A further improvement of the technical solution of the present invention is that the stimulation intervals initially increased in S3 are specifically: 1 millisecond, 1.5 milliseconds, 2 milliseconds, 2.5 milliseconds, 3 milliseconds, 3.5 milliseconds, 4 milliseconds, 5 milliseconds, 7 milliseconds, 10 milliseconds, 15 milliseconds, 20 milliseconds and 30 milliseconds; A further improvement of the technical solution of the present invention is that the three channels released by the preliminary increased stimulation interval in S3 include: preliminary channel 1, preliminary channel 2, and preliminary channel 3 in sequence, wherein preliminary channel 1 tracks the stimulation intensity required to produce an unconditional test response, preliminary channel 2 monitors subthreshold conditioned stimulation to ensure that no motor evoked potential response is produced and the subject remains relaxed, and preliminary channel 3 tracks the stimulation intensity required to produce motor evoked potential when subjected to subthreshold conditioned stimulation with the same intensity as channel 2.

[0012] A further improvement of the technical solution of the present invention is that the second increased stimulation interval in S3 is specifically 50 milliseconds, 100 milliseconds, 150 milliseconds, 200 milliseconds and 300 milliseconds; The two channels for the secondary increased stimulation interval in S3 include: secondary channel 1 and secondary channel 2, wherein secondary channel 1 tracks the stimulation intensity required to produce an unconditional test response, and secondary channel 2 tracks the stimulation intensity required to produce a target motor evoked potential when subjected to suprathreshold conditioned stimulation.

[0013] A further improvement of the technical solution of the present invention is that the time constant for calculating the intensity-duration in S1 specifically includes: By Weiss formula , and compared the ratio between 0.2 milliseconds and 1 milliseconds stimulation required to induce the same response, and used SR data to estimate the intensity-duration time constant, that is, the k value, where I is the stimulation current intensity, t is the stimulation time, and b is the base intensity, that is, the minimum current intensity required when the stimulation time is infinitely long.

[0014] A further improvement of the technical solution of the present invention is that in the S1-1, the target area of ​​the cerebral motor cortex specifically includes: the primary motor cortex area, the supplementary motor area and the premotor area.

[0015] Beneficial Effects Compared with the prior art, the beneficial effect of the present invention is that the stimulus-response curve of cortical stimulation is determined by increasing the intensity of magnetic stimulation to the following levels, and the central motor conduction time is calculated by the F-wave method based on the stimulus-response curve, the initial stimulation and threshold determination are completed, and subsequent threshold tracking is performed based on this technology, providing an efficient and accurate means of detecting the motor cortex function of the brain for the diagnosis of neurological diseases; Before applying transcranial magnetic stimulation to the motor cortex, an assessment of the peripheral nerves should be performed in advance to avoid damage or dysfunction of the peripheral nerves, which may result in the inability to accurately record muscle responses even if the cortical excitability is normal, thereby ensuring the accuracy of the motor cortex excitability assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A flowchart of the method for assessing motor cortex excitability based on threshold tracking magnetic stimulation; Figure 2 Schematic diagram of the TMS paradigm and stimulation mode configuration of the present invention; Figure 3 The stimulus-response curves of the test stimuli with a duration of 0.2 milliseconds and 1 millisecond recorded from the abductor pollicis brevis muscle after the median nerve at the wrist is electrically stimulated by the present invention; Figure 4 The present invention is a stimulation-response curve recorded from the abductor pollicis brevis muscle using transcranial magnetic stimulation; Figure 5 Workflow diagram for the method of assessing motor cortex excitability based on threshold-tracking magnetic stimulation. DETAILED DESCRIPTION

[0017] Various exemplary embodiments, features and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0018] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0019] In addition, in order to better illustrate the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In some examples, methods, means, and elements well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present application.

[0020] Example 1, please refer to the attached Figure 1 The present invention provides a method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation, the method comprising the following specific steps: S1: Assess peripheral nerves; electrically stimulate the median nerve at the wrist of the subject, record the resulting compound muscle action potential through surface electrodes, measure the peak-to-peak amplitude and onset latency of the compound muscle action potential, and record the stimulus-response curve, calculate the time constant of intensity-duration, record the F wave, and measure its onset latency.

[0021] See attached Figure 3 , Figure 3Stimulus-response curves for test stimuli of 0.2 and 1 ms duration recorded from the abductor pollicis brevis (APB) muscle after electrical stimulation of the median nerve at the wrist. The intensity-duration time constant was determined by comparing the ratio between the 0.2 and 1 ms stimuli.

[0022] S1 also includes the following preparatory steps, S1-1: pre-preparation; wait for the subject to be in a quiet and comfortable state, sit on a special chair, fix the subject's head position, aim the transcranial magnetic stimulation coil at the target area of ​​the brain's motor cortex, and paste the electromyographic motor on the target muscle group in the target area, and connect the electromyographic acquisition device. In S1-1, the target area of ​​the brain's motor cortex specifically includes: the primary motor cortex area, the supplementary motor area, and the premotor area. In the specific implementation of this embodiment, it is mainly for the abductor pollicis brevis muscle, paste the electromyographic electrode, connect the electromyographic acquisition device, and prepare for signal acquisition. Please refer to the attached Figure 2 , attached Figure 2 For the configuration of the TMS paradigm and stimulation pattern, cortical excitability was assessed by measuring changes in the stimulation intensity required to produce a 0.2 mV target magnetic motor evoked potential response recorded from the abductor pollicis brevis muscle.

[0023] The specific stimulation durations for electrical stimulation of the median nerve at the wrist in S1 are 0.2 milliseconds and 1 millisecond, and the specific number of F waves recorded in S1 is 10.

[0024] The time constants for calculating intensity-duration in S1 specifically include: By Weiss formula , and compared the ratio between 0.2 milliseconds and 1 milliseconds stimulation required to induce the same response, and used SR data to estimate the intensity-duration time constant, that is, the k value, where I is the stimulation current intensity, t is the stimulation time, and b is the base intensity, that is, the minimum current intensity required when the stimulation time is infinitely long.

[0025] In summary, the present application conducts a preliminary assessment of the peripheral nerves before applying transcranial magnetic stimulation to the motor cortex. The reason is that TMS generates motor evoked potentials by stimulating the cerebral cortex, and the recorded signals need to be transmitted to the muscles through peripheral nerves (such as motor nerves); if there is damage or dysfunction of the peripheral nerves (such as slowed conduction velocity, axonal rupture), even if the cortical excitability is normal, the muscle response may not be accurately recorded, resulting in deviation in the results, ensuring the accuracy of the motor cortex excitability assessment.

[0026] See attached Figure 4, S2: Determination of initial stimulation and threshold; Apply transcranial magnetic stimulation to the motor cortex based on the figure-8 coil, synchronously collect muscle response signals through the electromyography acquisition device, gradually adjust the stimulation intensity, and determine the stimulus-response curve of cortical stimulation by increasing the magnetic stimulation intensity to the following levels, and apply stimulation three times at each stimulation intensity level, and record the maximum motor evoked potential amplitude and motor evoked potential onset latency, and calculate the central motor conduction time according to the F wave method, where the central motor conduction time = , is the total latency of the F wave, that is, the time from stimulation to the appearance of the F wave. is the latency of the M wave, that is, the time from stimulation to the appearance of the M wave. MEP is the latency of TMS-induced MEP, T M is the M wave latency of wrist stimulation, T F This is the shortest latency of the F wave.

[0027] Attached Figure 4 Stimulus-response curve recorded from the abductor pollicis brevis muscle using transcranial magnetic stimulation. The horizontal dashed line indicates the 0.2 mV target output that was “tracked.”

[0028] In this embodiment, in the traditional double-pulse technique, the intensities of the conditioning stimulus and the test stimulus are kept constant, and the change in the amplitude of the motor evoked potential is measured, while in the threshold tracking TMS output (i.e., the motor evoked potential response) is fixed, and the change in the intensity of the test stimulus required to produce the target response after the subthreshold or suprathreshold conditioning stimulus is measured. The threshold tracking strategy adopted is based on the previous observation that the stimulus-response relationship is exponential.

[0029] Prior art has demonstrated that the relationship between the logarithm of the motor evoked potential amplitude and stimulation is nearly linear over a 100-fold response range from approximately 0.02 mV to 2 mV, and based on these observations, this embodiment selects a smaller target response of 0.2 mV (±20%) in the middle of the linear range and subsequently tracks it, where the resting motor threshold (RMT) is defined as the stimulation intensity required to produce and maintain a target motor evoked potential response (peak-to-peak value of 0.2 mV).

[0030] S3: Threshold tracking; repeat the S2 operation and increase the stimulation interval in sequence. The applied stimulation is delivered sequentially from the three channels. After the stimulation produces two consecutive evoked potential and movement evoked potential responses, the threshold tracking result is considered acceptable. Repeat the S2 operation again, and increase the stimulation interval in sequence again. The stimulation is delivered sequentially from the two channels.

[0031] In S1, short-interval intracortical inhibition (SICI) is mainly detected. Before the subthreshold conditioned stimulus is tested, the stimulus interval (ISI) increases in sequence. Then the initial stimulus intervals increased in S3 are: 1 millisecond, 1.5 milliseconds, 2 milliseconds, 2.5 milliseconds, 3 milliseconds, 3.5 milliseconds, 4 milliseconds, 5 milliseconds, 7 milliseconds, 10 milliseconds, 15 milliseconds, 20 milliseconds and 30 milliseconds. Subthreshold conditioned stimulus (intensity of 70% of resting motor threshold) will not trigger a response. Stimuli are delivered in sequence through three channels, as shown in the attached figure. Figure 2 shown.

[0032] Please refer to the attached Figure 2 The three channels released by the initial increase in the stimulation interval in S3 include: preliminary channel 1, preliminary channel 2, and preliminary channel 3, among which preliminary channel 1 tracks the stimulation intensity required to produce an unconditional test response (i.e., the resting motor threshold), preliminary channel 2 monitors the subthreshold conditioned stimulus to ensure that no motor evoked potential response is produced and the subject remains relaxed, and preliminary channel 3 tracks the stimulation intensity required to produce a motor evoked potential when subjected to a subthreshold conditioned stimulus of the same intensity as channel 2.

[0033] The threshold tracking result is considered acceptable. Specifically, when the test stimulus produces two consecutive evoked potential (MEP) responses, and the deviation of these two responses from the target response (0.2 mV) is within 20%, or they continue to fluctuate around the target value, the tracking is considered acceptable. The three channels are applied sequentially, with stimulation delivered every 5 to 10 seconds. Only when the tracking meets the target standard will the computer enter the next stimulation interval.

[0034] In S2, long-interval intracortical inhibition (LICI) was mainly detected. The suprathreshold conditioning stimulus (intensity was 120% of the resting motor threshold) was preceded by the suprathreshold test stimulus, and the ISI increased in sequence, specifically 50 ms, 100 ms, 150 ms, 200 ms, and 300 ms.

[0035] The two channels that are released at the second increased stimulus interval in S3 include: secondary channel 1 and secondary channel 2, where secondary channel 1 tracks the stimulus intensity (resting motor threshold) required to produce an unconditional test response, and secondary channel 2 tracks the stimulus intensity required to produce the target motor evoked potential when subjected to suprathreshold conditioned stimulation (intensity is 120% of the resting motor threshold).

[0036] The motor evoked potential induced by the conditioned stimulus was fully generated before the end of the shortest condition-test interval (50 ms). Therefore, the stimulation intensity required to produce the target motor evoked potential could be determined without online subtraction of the response to the conditioned stimulus, because the magnetic stimulation intensity was limited to an integer range of 1%-100% of the maximum stimulator output (MSO).

[0037] See attached Figure 2 , attached Figure 2 Middle channel 1: unconditioned test stimulus for measuring resting motor threshold (RMT); channel 2: conditioned stimulus, which can be set to subthreshold (70%RMT) when evaluating short-interval intracortical inhibition (SICI) or suprathreshold (120%RMT) when evaluating long-interval intracortical inhibition (LICI); channel 3: conditioned test stimulus at different interstimulus intervals (ISIs). SICI is measured by increasing the interstimulus interval from 1 to 30 ms, and LICI is measured by increasing the interstimulus interval from 50 to 300 ms.

[0038] S4: Data analysis and result output; Based on the data obtained from S1, S2, and S3, the statistical parameters of the mean and standard deviation of the excitability threshold are calculated to evaluate the stability of the excitability of the motor cortex of the brain. By comparing the changes in thresholds in different time periods, the dynamic trend of cortical excitability is determined.

[0039] Finally, the test results are output in the form of intuitive charts and detailed data reports for reference by clinicians or researchers. When calculating the degree of inhibition, the following formula is used: Inhibition degree = (conditional test stimulus intensity - resting motor threshold) / resting motor threshold × 100.

[0040] In summary, in the specific embodiments of the present application and the accompanying drawings, TMS stands for transcranial magnetic stimulation, CMAP stands for compound muscle action potential, SR stands for stimulus-response, MEP stands for motor evoked potential, RMT stands for resting motor threshold, CMCT stands for central motor conduction time, SICI stands for short-interval intracortical inhibition, ISI stands for stimulation interval, LICI stands for long-interval intracortical inhibition, MSO stands for maximum stimulator output, and APB stands for abductor pollicis brevis.

[0041] Example 2: This example further discloses the system composition used in this application, and the system specifically includes: Transcranial magnetic stimulator: It uses a device with high-precision stimulation intensity adjustment function, which can output magnetic pulses of different intensities and frequencies to stimulate specific areas of the brain's motor cortex. Its key parameters include maximum stimulation intensity, stimulation frequency range, pulse width, etc., which must meet the needs of clinical and scientific research for different stimulation modes. For example, the maximum stimulation intensity can reach 2-3T, the stimulation frequency range is 0.1-100Hz, and the pulse width is 100-300μs.

[0042] Myoelectric acquisition device: connected to the target muscle group, used to collect the electrical activity signals generated by the muscles under TMS stimulation. The device has high sensitivity and low noise characteristics, with a sampling frequency of no less than 1kHz, and can accurately capture weak changes in myoelectric signals. Its electrodes are made of silver-silver chloride material to ensure good conductivity and signal stability.

[0043] Data processing and analysis system: connected to the transcranial magnetic stimulator and the electromyography acquisition device, it receives and processes the collected data in real time. The built-in algorithm can filter, amplify, and extract features of the electromyography signal, and quickly calculate the excitability threshold of the motor cortex of the brain based on the set threshold judgment standard.

[0044] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium can store a computer program, and when the computer program is executed by the data processing unit, the invention content of the motor cortex excitability assessment method based on threshold tracking magnetic stimulation provided by the present invention and some or all of the steps in each embodiment can be executed. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0045] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present invention can be implemented by means of computer programs and their corresponding general hardware platforms. Based on such understanding, the technical solutions in the embodiments of the present invention can be essentially or partly contributed to the prior art in the form of computer programs, i.e., software products, which can be stored in a storage medium and include several instructions for enabling a device including a data processing unit (which can be a personal computer, a server, a single-chip microcomputer, an MCU or a network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.

[0046] The present invention provides a method for evaluating the excitability of the motor cortex based on threshold tracking magnetic stimulation. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for assessing motor cortex excitability based on threshold tracking magnetic stimulation, characterized in that: The method comprises the following specific steps: S1: Assess peripheral nerves; electrically stimulate the median nerve at the wrist of the subject, record the compound muscle action potential generated by the abductor pollicis brevis through surface electrodes, and measure the peak-to-peak amplitude and onset latency of the compound muscle action potential, and measure the peak-to-peak amplitude and onset latency of the compound muscle action potential for the electrical stimulation, record the stimulus-response curve, calculate the time constant of intensity-duration, record the F wave, and measure its onset latency; S2: Determination of initial stimulation and threshold; Apply transcranial magnetic stimulation to the motor cortex based on the figure-8 coil, synchronously collect muscle response signals through the electromyography acquisition device, gradually adjust the stimulation intensity, and determine the stimulus-response curve of cortical stimulation by increasing the magnetic stimulation intensity to the following levels. Apply stimulation three times at each stimulation intensity level, record the maximum motor evoked potential amplitude and motor evoked potential onset latency, and calculate the central motor conduction time according to the F-wave method; S3: Threshold tracking; repeat the S2 operation, and increase the stimulation interval in sequence, the applied stimulation is delivered in sequence by the three channels, after there are two consecutive evoked potential and motor evoked potential responses produced by the stimulation, the threshold tracking result is considered acceptable, and then repeat the S2 operation, the stimulation interval is increased in sequence again, and the stimulation is delivered in sequence by the two channels; S4: Data analysis and result output; Based on the data obtained in S1, S2 and S3, the statistical parameters of the mean and standard deviation of the excitability threshold are calculated to evaluate the stability of the excitability of the motor cortex of the brain, and the dynamic trend of the cortical excitability is determined by comparing the threshold changes in different time periods.

2. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 1, characterized in that: The S1 also includes the following preparatory steps: S1-1: Pre-preparation: After the subject is in a quiet and comfortable state, fix the subject's head position, aim the transcranial magnetic stimulation coil at the target area of ​​the motor cortex of the brain, and stick electromyographic electrodes on the target muscle groups in the target area, and connect the electromyographic acquisition device.

3. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 1, characterized in that: The specific stimulation time limits for electrically stimulating the median nerve at the wrist in S1 are: 0.2 milliseconds and 1 millisecond; The number of F waves recorded in S1 is specifically 10.

4. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 1, characterized in that: The figure-8 coil in S2 applies transcranial magnetic stimulation to the motor cortex, including the following specific settings: The size of the figure-8 coil is 90 mm; The direction of the figure-8 coil is set to induce the current to flow in the back-to-front direction; The figure-of-eight coil was initially placed at the center of the top of the head and then moved in the anterior-posterior and lateral-lateral directions to find the optimal position that could elicit the maximum amplitude response from the APB.

5. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 1, characterized in that: The transcranial magnetic stimulation applied to the motor cortex based on the figure-8 coil in S2 is a single pulse stimulation, and the stimulation-response curve in S2 specifically includes 60%, 80%, 90%, 100%, 110%, 120%, 130%, 140% and 150% of the resting motor threshold.

6. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 1, characterized in that: The stimulation intervals initially increased in the S3 are specifically: 1 millisecond, 1.5 milliseconds, 2 milliseconds, 2.5 milliseconds, 3 milliseconds, 3.5 milliseconds, 4 milliseconds, 5 milliseconds, 7 milliseconds, 10 milliseconds, 15 milliseconds, 20 milliseconds and 30 milliseconds.

7. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 6, characterized in that: The three channels released by the preliminary increased stimulation interval in S3 include: preliminary channel 1, preliminary channel 2, and preliminary channel 3, wherein preliminary channel 1 tracks the stimulation intensity required to produce an unconditional test response, preliminary channel 2 monitors subthreshold conditioned stimulation, and preliminary channel 3 tracks the stimulation intensity required to produce a motor evoked potential when subjected to a subthreshold conditioned stimulation with the same intensity as channel 2.

8. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 1, characterized in that: The second increased stimulation intervals in S3 are specifically 50 milliseconds, 100 milliseconds, 150 milliseconds, 200 milliseconds and 300 milliseconds; The two channels for the secondary increased stimulation interval in S3 include: secondary channel 1 and secondary channel 2, wherein secondary channel 1 tracks the stimulation intensity required to produce an unconditional test response, and secondary channel 2 tracks the stimulation intensity required to produce a target motor evoked potential when subjected to suprathreshold conditioned stimulation.

9. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 1, characterized in that: The time constant for calculating the intensity-duration in S1 specifically includes: By Weiss formula , and compared the ratio between 0.2 milliseconds and 1 milliseconds stimulation required to induce the same response, and used SR data to estimate the intensity-duration time constant, that is, the k value, where I is the stimulation current intensity, t is the stimulation time, and b is the base intensity, that is, the minimum current intensity required when the stimulation time is infinitely long.

10. The method for evaluating motor cortex excitability based on threshold tracking magnetic stimulation according to claim 2, characterized in that: In the S1-1, the target areas of the cerebral motor cortex specifically include: the primary motor cortex area, the supplementary motor area and the premotor area.

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