Threshold-based tracking of motor cortex excitability

Abstract

This invention discloses a method for assessing motor cortical excitability based on threshold-tracking magnetic stimulation, relating to the field of biomedical engineering technology. The method includes the following steps: electrical stimulation of the median nerve in the subject's wrist; recording on the abductor pollicis brevis (APB) muscle; recording the stimulus-response curve; determining the cortical stimulus-response (SR) curve by increasing the magnetic stimulation intensity to the specified levels; calculating the statistical parameters of the mean and standard deviation of the excitability threshold; and determining the dynamic trend of cortical excitability. This invention determines the cortical stimulus-response curve by increasing the magnetic stimulation intensity to the specified levels, and calculates the central motor conduction time based on the stimulus-response curve using the F-wave method, thus completing the initial stimulus and threshold determination. Subsequent threshold tracking is then performed based on this technique, providing an efficient and accurate means of detecting motor cortical function for the diagnosis of neurological diseases.

Description

Technical Field

[0001] This invention relates to the field of biomedical engineering technology, specifically to a method for assessing the excitability of the motor cortex based on threshold-tracking magnetic stimulation. Background Technology

[0002] Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease of the central nervous system. At the pathophysiological level, ALS is a multi-stage process. Increasing evidence suggests that ALS originates in the motor cortex, where hyperexcitability mediates lower motor neuron degeneration through a transsynaptic glutamatergic excitotoxic mechanism. Increased excitability of the motor cortex is an early and intrinsic characteristic of both sporadic and familial ALS.

[0003] Transcranial magnetic stimulation (TMS) is a neurophysiological technique that provides a non-invasive and painless method for assessing cortical function. As a non-invasive detection method, TMS offers high temporal and spatial resolution. However, conventional TMS techniques often cannot track changes in excitability in the motor cortex in real time, dynamically, and accurately, limited by fluctuations in the amplitude of motor evoked potentials, making it difficult to meet the needs of clinical and research applications for precise assessment of motor cortex function. Threshold-tracking TMS technology has emerged to address this need, as it can easily determine whether ALS patients have increased cortical excitability. Using threshold-tracking TMS to detect cortical excitability, and given that high cortical excitability in ALS patients has been established as a powerful diagnostic biomarker, threshold-tracking TMS technology helps in the diagnosis and differential diagnosis of ALS, and distinguishes it from ALS-like syndromes. TMS technology can assess cortical excitability; it is a non-invasive neurophysiological 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. Specifically, a subthreshold conditioned stimulus was applied at an interstimulus interval (ISI) of 1–5 ms, followed by multiple conditioned test stimuli that generated multiple motor evoked potentials (MEPs), and the degree of decrease in MEP amplitude was recorded each time. This parameter is called short-interval intracortical inhibition (SICI), and it is likely a biomarker of intermediate inhibitory cortical neurons generated through the GABA-A receptor circuit. The most commonly used parameter is short-interval intracortical inhibition (SICI). Another parameter, long-interval intracortical inhibition (LICI), occurs at stimulation intervals of 50–300 ms and peaks at 150 ms.Given that constant stimulation TMS technology may be limited by changes in the amplitude of motor evoked potentials (SEPs), a "paired pulse TMS mode" exists. This mode involves first applying a subthreshold conditioned stimulus, followed by a conditioned test stimulus to generate a motor evoked potential (SEP), and repeating this process multiple times to gradually achieve the optimal effect. Specifically, a fixed amplitude of one SEP is tracked by a test stimulus, so that SICI is predicted by a larger conditioned test stimulus intensity to generate and maintain the target SEP response. Compared with constant stimulation technology, threshold tracking TMS technology improves reproducibility and shortens acquisition time. This technology has revealed great potential for the study of motor cortical circuit function. Therefore, this application provides a further method for assessing motor cortical excitability based on threshold tracking magnetic stimulation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for assessing the excitability of the motor cortex based on threshold-tracking magnetic stimulation, thus solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides a method for assessing the excitability of the motor cortex based on threshold-tracking magnetic stimulation, the method comprising the following specific steps:

[0006] S1: Assess peripheral nerves; Electrically stimulate the median nerve in the subject's wrist, record the resulting compound muscle action potentials using surface electrodes, and measure the peak-to-peak amplitude and onset latency of the compound muscle action potentials. For the electrical stimulation, measure the peak-to-peak amplitude and onset latency of the compound muscle action potentials, record the stimulus-response curve, calculate the intensity-duration time constant, record the F wave, and measure its onset latency.

[0007] S2: Determination of initial stimulus and threshold; Transcranial magnetic stimulation (TMS) is applied to the motor cortex using a figure-eight coil, and muscle response signals are simultaneously acquired using an electromyography (EMG) acquisition device. The stimulation intensity is gradually adjusted, and the stimulus-response curve of the cortex is determined by increasing the magnetic stimulation intensity to the following levels. Three stimuli are applied at each stimulation intensity level, and the maximum amplitude and onset latency of the motor evoked potential are recorded. The central motor conduction time is calculated using the F-wave method. In the traditional dual-pulse technique, the intensity of the conditioned stimulus and the test stimulus are kept constant, and the change in the amplitude of the motor evoked potential is measured. In contrast, the threshold-tracking TMS output is fixed, and the change in the intensity of the test stimulus required to produce the target response after subthreshold or suprathreshold conditioned stimulation is measured. The threshold-tracking strategy is based on previous observations that the stimulus-response relationship is exponential.

[0008] S3: Threshold tracking; repeat the S2 operation and increase the stimulation interval sequentially. The applied stimulus is emitted sequentially from the three channels. If the stimulus produces two consecutive evoked potentials and a motor evoked potential response, the threshold tracking result is considered acceptable. Repeat the S2 operation again, and increase the stimulation interval sequentially. The stimulus is emitted sequentially from the two channels.

[0009] S4: Data Analysis and Result Output; Based on the data obtained in S1, S2 and S3, calculate the statistical parameters of the average value and standard deviation of the excitability threshold, assess the stability of the excitability of the motor cortex of the brain, and judge the dynamic trend of cortical excitability by comparing the threshold changes in different time periods.

[0010] A further improvement to the technical solution of the present invention is that step S1 further includes the following pre-preparation steps:

[0011] S1-1: Preparation; After the subject is in a quiet and comfortable state, fix the subject's head position, align the transcranial magnetic stimulation coil with the target area of ​​the brain's motor cortex, attach electromyographic electrodes to the target muscle group in the target area, and connect the electromyographic acquisition device.

[0012] A further improvement of the technical solution of the present invention is that the specific stimulation time limit for the median nerve of the wrist in S1 is 0.2 milliseconds and 1 millisecond;

[0013] The number of F waves recorded in S1 is specifically 10.

[0014] A further improvement to the technical solution of the present invention is that the application of transcranial magnetic stimulation to the motor cortex by the figure-eight coil in S2 includes the following specific settings:

[0015] The figure-eight coil measures 90 millimeters.

[0016] The figure-eight coil is set to induce current to flow in the back-forward direction;

[0017] The figure-eight coil is initially placed at the center of the top of the head, and then moved in the front-back and inward-outward directions to find the optimal position that can induce the maximum amplitude response from the APB muscles.

[0018] A further improvement of the technical solution of the present invention is that, in S2, the transcranial magnetic stimulation applied to the motor cortex based on the figure-eight coil 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.

[0019] A further improvement to the technical solution of the present invention is that the stimulation interval initially added in S3 is 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;

[0020] A further improvement of the technical solution of the present invention is that the three channels emitted by the initially added stimulation interval in S3 are: initial channel 1, initial channel 2, and initial channel 3, wherein the initial channel 1 tracks the stimulation intensity required to generate an unconditional test response, the initial channel 2 monitors subthreshold conditioned stimuli to ensure that no motor evoked potential response is generated and the subject remains relaxed, and the initial channel 3 tracks the stimulation intensity required to generate a motor evoked potential when subjected to a subthreshold conditioned stimulus of the same intensity as channel 2.

[0021] A further improvement to the technical solution of the present invention is that the stimulation intervals added twice in S3 are specifically 50 milliseconds, 100 milliseconds, 150 milliseconds, 200 milliseconds, and 300 milliseconds;

[0022] The two channels for the secondary stimulation interval in S3 include: secondary channel 1 and secondary channel 2, wherein secondary channel 1 tracks the stimulation intensity required to generate an unconditional test response, and secondary channel 2 tracks the stimulation intensity required to generate a target motor evoked potential when subjected to a suprathreshold conditioned stimulus.

[0023] A further improvement to the technical solution of the present invention is that the time constant for calculating the intensity-duration in S1 specifically includes:

[0024] Through Weiss formula The ratio between 0.2 ms and 1 ms stimuli required to elicit the same response was compared, and SR data were used to estimate the intensity-duration time constant, i.e., the k value, where I is the stimulation current intensity, t is the stimulation time, and b is the base intensity, i.e., the minimum current intensity required when the stimulation time is infinitely long.

[0025] A further improvement of the technical solution of the present invention is that, 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.

[0026] Beneficial effects

[0027] Compared with the prior art, the beneficial effects of the present invention are that by increasing the magnetic stimulation intensity to the following level to determine the stimulus-response curve of cortical stimulation, and calculating the central motor conduction time based on the stimulus-response curve using the F-wave method, the initial stimulus and threshold determination is completed, and subsequent threshold tracking is performed on this technology, providing an efficient and accurate means of detecting the function of the brain's motor cortex for the diagnosis of neurological diseases.

[0028] Before applying transcranial magnetic stimulation to the motor cortex, a preliminary assessment of the peripheral nerves should be performed to avoid situations where damage or dysfunction of the peripheral nerves may occur, which could lead to inaccurate recording of muscle responses even if cortical excitability is normal. This ensures the accuracy of motor cortex excitability assessment. Attached Figure Description

[0029] Figure 1 This is a flowchart of an operational method for assessing the excitability of the motor cortex based on threshold-tracking magnetic stimulation.

[0030] Figure 2 This is a schematic diagram illustrating the TMS paradigm and stimulation mode configuration of the present invention.

[0031] Figure 3 The present invention provides stimulation-response curves for test stimuli with durations of 0.2 ms and 1 ms recorded from the abductor pollicis brevis muscle after electrical stimulation of the median nerve at the wrist.

[0032] Figure 4 This is the stimulus-response curve recorded from the abductor pollicis brevis muscle using transcranial magnetic stimulation according to the present invention;

[0033] Figure 5 This is a flowchart of a method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation. Detailed Implementation

[0034] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0035] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0036] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, and elements well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0037] Example 1, please refer to the appendix. Figure 1 This invention provides a method for assessing the excitability of the motor cortex based on threshold-tracking magnetic stimulation, the method comprising the following specific steps:

[0038] S1: Assess peripheral nerves; Electrically stimulate the median nerve in the subject's wrist, record the resulting compound muscle action potentials (CMAPs) using surface electrodes, and measure the peak-to-peak amplitude and onset latency of the CAPs. For the electrical stimulation, measure the peak-to-peak amplitude and onset latency of the CAPs, record the stimulus-response curve, calculate the intensity-duration time constant, record the F wave, and measure its onset latency.

[0039] See attached document Figure 3 , Figure 3 Stimulus-response curves for test stimuli with durations of 0.2 ms and 1 ms were 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 ms and 1 ms stimuli.

[0040] S1 also includes the following preparatory steps: S1-1: Preparatory work; After the subject is in a quiet and comfortable state, sit in a specially designed chair, fix the subject's head position, align the transcranial magnetic stimulation coil with the target area of ​​the brain's motor cortex, and attach electromyographic electrodes to the target muscle group in the target area, connecting 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 this embodiment, it mainly refers to the abductor pollicis brevis muscle. Attach electromyographic electrodes, connect the electromyographic acquisition device, and prepare for signal acquisition. Please refer to the appendix. Figure 2 , attached Figure 2 To configure the TMS paradigm and stimulation pattern, cortical excitability was assessed by measuring the change in stimulus intensity required to generate a 0.2 mV target magnetic motion evoked potential response, which was recorded from the abductor pollicis brevis muscle.

[0041] The specific stimulation durations for the median nerve at the wrist in S1 are 0.2 milliseconds and 1 millisecond, and the number of F waves recorded in S1 is 10.

[0042] The time constant for estimating intensity-duration in S1 specifically includes:

[0043] Through Weiss formula The ratio between 0.2 ms and 1 ms stimuli required to elicit the same response was compared, and SR data were used to estimate the intensity-duration time constant, i.e., the k value, where I is the stimulation current intensity, t is the stimulation time, and b is the base intensity, i.e., the minimum current intensity required when the stimulation time is infinitely long.

[0044] In summary, this application conducts a preliminary assessment of the peripheral nerves before applying transcranial magnetic stimulation to the motor cortex. This is because 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 or axonal breakage), even if the cortical excitability is normal, the muscle response may not be accurately recorded, leading to biased results. Therefore, this approach ensures the accuracy of the assessment of motor cortex excitability.

[0045] See attached document Figure 4 S2: Determination of initial stimulus and threshold; Transcranial magnetic stimulation (TMS) is applied to the motor cortex using a figure-eight coil, and muscle response signals are simultaneously acquired using an electromyography (EMG) acquisition device. The stimulation intensity is gradually adjusted, and the stimulus-response curve of the cortex is determined by increasing the magnetic stimulation intensity to the following levels. Three stimuli are applied at each stimulation intensity level, and the maximum amplitude and onset latency of the motor evoked potential are recorded. The central motor conduction time is calculated using the F-wave method, where the central motor conduction time = , The total latency of the F wave is the time from stimulation to the appearance of the F wave. This refers to the latency period of the M-wave, which is the time from stimulation to the appearance of the M-wave. T1 MEP TMS-induced MEP latency period, T M For wrist stimulation, the M-wave latency, T F This is the shortest latency period for the F wave.

[0046] Appendix Figure 4 The stimulation-response curves recorded from the abductor pollicis brevis muscle using transcranial magnetic stimulation are shown, with the horizontal dashed line representing the 0.2 mV target output that was "tracked".

[0047] In this embodiment, the traditional dual-pulse technique keeps the intensity of the conditioned stimulus and the test stimulus constant, and measures the change in the amplitude of the motor evoked potential. The threshold-tracking TMS output (i.e., the motor evoked potential response) is fixed, and measures the change in the intensity of the test stimulus required to produce the target response after a subthreshold or suprathreshold conditioned stimulus. The threshold-tracking strategy is based on previous observations that the stimulus-response relationship is exponential.

[0048] Existing technology has confirmed that the relationship between the logarithm of the motor evoked potential amplitude and the stimulus is nearly linear within a 100-fold response range from approximately 0.02 mV to 2 mV. Based on these observations, this embodiment selects a smaller target response of 0.2 mV (±20%), the midpoint of this linear range, and then tracks it. The resting motor threshold (RMT) is defined as the stimulus intensity required to generate and maintain the target motor evoked potential response (peak-to-peak value of 0.2 mV).

[0049] S3: Threshold tracking; repeat S2 operation and increase the stimulation interval sequentially. The applied stimulus is emitted sequentially from the three channels. If the stimulus produces two consecutive evoked potentials and a motor evoked potential response, the threshold tracking result is considered acceptable. Repeat S2 operation again, and increase the stimulation interval sequentially. The stimulus is emitted sequentially from two channels.

[0050] In S1, short-interval intracortical inhibition (SICI) is primarily detected. Subthreshold conditioned stimuli are delivered before the test stimulus, with the stimulus interval (ISI) increasing sequentially. Therefore, the initial increase in stimulus intervals in S3 is as follows: 1 ms, 1.5 ms, 2 ms, 2.5 ms, 3 ms, 3.5 ms, 4 ms, 5 ms, 7 ms, 10 ms, 15 ms, 20 ms, and 30 ms. Subthreshold conditioned stimuli (at 70% of the resting motor threshold) do not elicit a response. Stimuli are delivered sequentially through three channels, as shown in the attached diagram. Figure 2 As shown.

[0051] Please refer to the appendix. Figure 2 The three channels emitted by the initial stimulation interval in S3 are: initial channel 1, initial channel 2, and initial channel 3. Initial channel 1 tracks the stimulus intensity required to produce an unconditional test response (i.e., the resting motor threshold), initial channel 2 monitors subthreshold conditioned stimuli to ensure that no motor evoked potential response is produced and the subject remains relaxed, and initial channel 3 tracks the stimulus intensity required to produce a motor evoked potential when subjected to a subthreshold conditioned stimulus of the same intensity as channel 2.

[0052] The threshold tracking result is considered acceptable when the test stimulus produces two consecutive evoked potential motor evoked potential responses, and the deviation of these two responses from the target response (0.2 mV) is within 20%, or when they continuously fluctuate around the target value. The three channels are applied sequentially, with a stimulus delivered every 5 to 10 seconds. The computer will only move to the next stimulus interval when the tracking meets the target criteria.

[0053] In S2, the main focus is on detecting long-interval intracortical inhibition (LICI). Before the suprathreshold conditioned stimulus (120% of the resting motor threshold), the ISI increases sequentially, specifically at 50 ms, 100 ms, 150 ms, 200 ms, and 300 ms.

[0054] The two channels for the additional stimulation interval in S3 are: secondary channel 1 and secondary channel 2. Secondary channel 1 tracks the stimulus intensity (resting motion threshold) required to generate an unconditional test response, while secondary channel 2 tracks the stimulus intensity required to generate a target motor evoked potential when subjected to a suprathreshold conditioned stimulus (intensity of 120% of the resting motion threshold).

[0055] The motor evoked potentials induced by the conditioned stimulus are fully generated before the shortest condition-test interval (50 milliseconds) ends. Therefore, the stimulus intensity required to generate the target motor evoked potential can be determined without subtracting the response to the conditioned stimulus online, since the magnetic stimulation intensity is limited to the integer range of 1%-100% of the maximum stimulator output (MSO).

[0056] See attached document Figure 2 , attached Figure 2 Channel 1: Unconditional test stimulus, used to measure the resting motor threshold (RMT); Channel 2: Conditioned stimulus, which can be set subthreshold (70% RMT) when assessing short-interval intracortical inhibition (SICI) and suprathreshold (120% RMT) when assessing long-interval intracortical inhibition (LICI); Channel 3: Conditioned test stimulus at different stimulus intervals (ISIs). Short-interval intracortical inhibition (SICI) is measured by increasing the stimulus interval from 1 ms to 30 ms, and long-interval intracortical inhibition (LICI) is measured by increasing the stimulus interval from 50 ms to 300 ms.

[0057] S4: Data Analysis and Results Output; Based on the data obtained from S1, S2 and S3, calculate the statistical parameters of the mean and standard deviation of the excitability threshold, assess the stability of the excitability of the motor cortex of the brain, and judge the dynamic trend of cortical excitability by comparing the threshold changes at different time periods.

[0058] The test results will be output in the form of intuitive charts and detailed data reports for clinicians or researchers to refer to. The degree of inhibition is calculated using the following formula: Degree of Inhibition = (Conditional Test Stimulus Intensity - Resting Motor Threshold) / Resting Motor Threshold × 100.

[0059] In summary, in the specific embodiments and accompanying drawings of this application, TMS represents transcranial magnetic stimulation, CMAP represents compound muscle action potential, SR represents stimulus-response, MEP represents motor evoked potential, RMT represents resting motor threshold, CMCT represents central motor conduction time, SICI represents short-interval intracortical inhibition, ISI represents stimulation interval, LICI represents long-interval intracortical inhibition, MSO represents maximum stimulator output, and APB represents abductor pollicis brevis.

[0060] Example 2 further discloses the system composition used in this application. The system specifically includes:

[0061] Transcranial magnetic stimulation (TMS) devices employ high-precision stimulation intensity adjustment to output magnetic pulses of varying intensities and frequencies to stimulate specific areas of the brain's motor cortex. Key parameters include maximum stimulation intensity, stimulation frequency range, and pulse width, which must meet the needs of clinical and research applications for different stimulation modes. For example, the maximum stimulation intensity can reach 2-3 T, the stimulation frequency range is 0.1-100 Hz, and the pulse width is 100-300 μs.

[0062] Electromyography (EMG) acquisition device: Connected to the target muscle group, it is used to acquire the electrical activity signals generated by the muscles under TMS stimulation. This device features high sensitivity and low noise, with a sampling frequency of no less than 1 kHz, enabling it to accurately capture weak EMG signal changes. Its electrodes are made of silver chloride, ensuring good conductivity and signal stability.

[0063] Data processing and analysis system: Connected to the transcranial magnetic stimulation (TMS) device and electromyography (EMG) acquisition device, it receives and processes the acquired data in real time. Built-in algorithms can filter, amplify, and extract features from EMG signals, and quickly calculate the excitability threshold of the cerebral motor cortex based on set threshold judgment criteria.

[0064] In its specific implementation, this application provides a computer storage medium and a corresponding data processing unit. The computer storage medium is capable of storing a computer program, which, when executed by the data processing unit, can run the invention content of the threshold-tracking magnetic stimulation-based motor cortex excitability assessment method provided by this invention, as well as some or all of the steps in various embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0065] Those skilled in the art will clearly understand that the technical solutions in the embodiments of the present invention can be implemented using computer programs and their corresponding general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of computer programs, i.e., software products. These computer program software products can be stored in a storage medium and include several instructions to cause a device containing a data processing unit (which may be a personal computer, server, microcontroller, MCU, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0066] This invention provides a method for assessing the excitability of the motor cortex based on threshold-tracking magnetic stimulation. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation, characterized in that, The method includes the following specific steps: S1: Assess peripheral nerves; Electrically stimulate the median nerve in the subject's wrist, record the compound muscle action potential generated by the abductor pollicis brevis muscle through surface electrodes, measure the peak-to-peak amplitude and onset latency of the compound muscle action potential, record the electrical stimulation-response curve, calculate the intensity-duration time constant, record the F wave, and measure its onset latency. S2: Determination of initial stimulus and threshold; Transcranial magnetic stimulation (TMS) is applied to the motor cortex using a figure-eight coil. Muscle response signals are simultaneously acquired using an electromyography (EMG) acquisition device. The intensity of the magnetic stimulation is gradually adjusted. The cortical magnetic stimulation-response curve is determined by increasing the intensity of the magnetic stimulation. Three magnetic stimulations are applied at each intensity level, and the amplitude and latency of motor evoked potentials (MEPs) are recorded. The central motor conduction time is calculated using the F-wave method, where the central motor conduction time = , The total latency of the F wave is the time from magnetic stimulation to the appearance of the F wave. The latency of the M wave is the time from magnetic stimulation to the appearance of the M wave. Among them, TMEP is the latency of MEP induced by TMS, TM is the latency of M wave induced by wrist stimulation, and TF is the shortest latency of F wave. S3: Threshold tracking; repeat the S2 operation and increase the magnetic stimulation interval sequentially. The applied magnetic stimulation is delivered sequentially from three channels. After the magnetic stimulation produces two consecutive evoked potentials and motion evoked potential responses, the threshold tracking result is considered acceptable. Repeat the S2 operation again, and increase the magnetic stimulation interval sequentially again. The magnetic stimulation is delivered sequentially from two channels. S4: Data analysis and result output; Based on the data obtained in S1, S2 and S3, calculate the statistical parameters of the average value and standard deviation of the threshold, evaluate the stability of motor cortex excitability, and judge the dynamic trend of cortical excitability by comparing the threshold changes in different time periods.

2. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 1, characterized in that, S1 also includes the following pre-preparation steps: S1-1: Preparation; After the subject is in a quiet and comfortable state, fix the subject's head position, align the figure-eight coil with the target area of ​​the motor cortex, attach electromyography electrodes to the target muscle group in the target area, and connect the electromyography acquisition device.

3. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 1, characterized in that, The specific stimulation duration for the median nerve in the wrist in S1 is 0.2 milliseconds and 1 millisecond; The number of F waves recorded in S1 is specifically 10.

4. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 1, characterized in that, The figure-eight coil in S2 applies transcranial magnetic stimulation to the motor cortex, including the following specific settings: The figure-eight coil measures 90 mm. The figure-eight coil is set to induce current to flow in the back-forward direction; The figure-eight coil is initially placed at the center of the top of the head, and then moved in the front-back and inward-outward directions to find the optimal position that can induce the maximum amplitude response from the abductor pollicis brevis muscle.

5. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 1, characterized in that, In S2, the transcranial magnetic stimulation applied to the motor cortex based on the figure-eight coil is a single-pulse magnetic stimulation, and the magnetic stimulation-response curve in S2 specifically includes the resting motor threshold.

6. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 1, characterized in that, The initial increase in the magnetic stimulation interval in S3 is specifically as follows: 1 ms, 1.5 ms, 2 ms, 2.5 ms, 3 ms, 3.5 ms, 4 ms, 5 ms, 7 ms, 10 ms, 15 ms, 20 ms, and 30 ms.

7. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 6, characterized in that, The three channels initially released in S3 by the initial increase in magnetic stimulation interval include: initial channel 1, initial channel 2, and initial channel 3. Initial channel 1 tracks the magnetic stimulation intensity required to generate an unconditional test response, initial channel 2 monitors subthreshold conditional magnetic stimulation, and initial channel 3 tracks the magnetic stimulation intensity required to generate a motor evoked potential when subjected to subthreshold conditional magnetic stimulation with the same intensity as initial channel 2.

8. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 1, characterized in that, The magnetic stimulation interval in S3 is increased twice, specifically to 50 milliseconds, 100 milliseconds, 150 milliseconds, 200 milliseconds, and 300 milliseconds; The magnetic stimulation interval in S3 is increased twice by two channels, which include: secondary channel 1 and secondary channel 2. Secondary channel 1 tracks the stimulation intensity required to generate an unconditional test response, and secondary channel 2 tracks the stimulation intensity required to generate a target motor evoked potential when subjected to a suprathreshold conditioned stimulus.

9. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 1, characterized in that, The time constant for estimating intensity-duration in S1 specifically includes: Through Weiss formula The ratio of 0.2 ms to 1 ms electrical stimulation required to induce the same response was compared, and SR data were used to estimate the intensity-duration time constant, i.e., the k value, where I is the electrical stimulation current intensity, t is the electrical stimulation time, and b is the base intensity, i.e., the minimum current intensity required when the electrical stimulation time is infinitely long.

10. The method for assessing motor cortex excitability based on threshold-tracking magnetic stimulation according to claim 2, characterized in that, In S1-1, the target area of ​​the motor cortex specifically includes: the primary motor cortex area, the auxiliary motor area, and the premotor area.

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