Slow-oscillatory transcranial direct current stimulation can induce bidirectional shifts in motor cortical excitability in awake humans

Constant transcranial direct stimulation (c-tDCS) of the primary motor hand area (M1_HAND) can induce bidirectional shifts in motor cortical excitability depending on the polarity of tDCS. Recently, anodal slow oscillation stimulation at a frequency of 0.75 Hz has been shown to augment intrinsic slow oscillations during sleep and theta oscillations during wakefulness. To embed this new type of stimulation into the existing tDCS literature, we aimed to characterize the after effects of slowly oscillating stimulation (so-tDCS) on M1_HAND excitability and to compare them to those of c-tDCS. Here we show that so-tDCS at 0.8 Hz can also induce lasting changes in corticospinal excitability during wakefulness. Experiment 1. In 10 healthy awake individuals, we applied c-tDCS or so-tDCS to left M1_HAND on separate days. Each tDCS protocol lasted for 10 min. Measurements of motor evoked potentials (MEPs) confirmed previous work showing that anodal c-tDCS at an intensity of 0.75 mA (maximal current density 0.0625 mA/cm2) enhanced corticospinal excitability, while cathodal c-tDCS at 0.75 mA reduced it. The polarity-specific shifts in excitability persisted for at least 20 min after c-tDCS. Using a peak current intensity of 0.75 mA, neither anodal nor cathodal so-tDCS had consistent effects on corticospinal excitability. Experiment 2. In a separate group of ten individuals, peak current intensity of so-tDCS was raised to 1.5 mA (maximal current density 0.125 mA/cm2) to match the total amount of current applied with so-tDCS to the amount of current that had been applied with c-tDCS at 0.75 mA in Experiment 1. At peak intensity of 1.5 mA, anodal and cathodal so-tDCS produced bidirectional changes in corticospinal excitability comparable to the after effects that had been observed after c-tDCS at 0.75 mA in Experiment 1. The results show that so-tDCS can induce bidirectional shifts in corticospinal excitability in a similar fashion as c-tDCS if the total amount of applied current during the tDCS session is matched.     

Corticospinal excitability and sleep: a motor threshold assessment by transcranial magnetic stimulation after awakenings from REM and NREM sleep

Transcranial magnetic stimulation (TMS) is a recently established technique in the neurosciences that allows the non-invasive assessment, among other parameters, of the excitability of motor cortex. Up to now, its application to sleep research has been very scarce and because of technical problems it provided contrasting results. In fact delivering one single suprathreshold magnetic stimulus easily awakes subjects, or lightens their sleep. For this reason, in the present study we assessed motor thresholds (MTs) upon rapid eye movement (REM) and non-rapid eye movement (NREM) sleep awakenings, both in the first and in the last part of the night. Taking into account that a full re-establishment of wake regional brain activity patterns upon awakening from sleep needs up to 20-30 min, it is possible to make inferences about the neurophysiological characteristics of the different sleep stages by analyzing the variables of interest immediately after provoked awakenings. Ten female volunteers slept in the lab for four consecutive nights. During the first night the MTs were collected, following a standardized procedure: 5 min before lights off, upon stage 2 awakening (second NREM period), upon REM sleep awakening (second REM period), upon the final morning awakening (always from stage 2). Results showed that MTs increased linearly from presleep wakefulness to REM sleep awakenings, and from the latter to stage 2 awakenings. There was also a time-of-night effect on MTs upon awakening from stage 2, indicating that MTs decreased from the first to the second part of the night. The increase in corticospinal excitability across the night, which parallels the fulfillment of sleep need, is consistent with the linear decrease of auditory arousal thresholds during the night. The maximal reduction of corticospinal excitability during early NREM sleep can be related to the hyperpolarization of thalamocortical neurons, and is in line with the decreased metabolic activity of motor cortices during this sleep stage. On the contrary, the increase of MTs upon REM sleep awakenings should reflect peripheral factors. We conclude that our findings legitimate the introduction of the TMS technique as a new proper tool in sleep research.     

Cortical inhibition in Parkinson's disease: new insights from early, untreated patients

Transcranial magnetic stimulation (TMS) has opened important perspectives on the pathophysiological bases and potential targets of treatment strategies for idiopathic Parkinson’s disease (IPD). Studies have been mainly focusing on motor cortical inhibitory phenomena. However, differences in patients and methods caused several discrepancies, particularly on the so-called long-latency cortical inhibition (LICI). We wanted to challenge such controversies by studying early, drug-naïve patients, and by reproducing the original method that detected a pathologic LICI in IPD.     

An enhanced level of motor cortical excitability during the control of human standing

Aim: The study examined the role of the motor cortex in the control of human standing. Methods: Subjects (n = 15) stood quietly with or without body support. The supported standing condition enabled subjects to stand with a reduced amount of postural sway. Peripheral electrical stimulation, transcranial magnetic stimulation (TMS) or transcranial electrical stimulation (TES) was applied to elicit a soleus (SOL) H‐reflex, or motor‐evoked potentials (MEPs) in the SOL and the tibialis anterior (TA). Trials were grouped based on the standing condition (i.e. supported vs. normal) as well as sway direction (i.e. forward and backward) while subjects were standing normally. Results: During normal when compared to supported standing, the SOL H‐reflex was depressed (?11 ± 4%), while the TMS‐evoked MEPs from the SOL and TA were facilitated (35 ± 11% for the SOL, 51 ± 15% for the TA). TES‐evoked SOL and TA MEPs were, however, not different between the normal and supported standing conditions. The data based on sway direction indicated that the SOL H‐reflex, as well as the SOL TMS‐ and TES‐evoked MEPs were all greater during forward when compared to backward sway. In contrast, the TMS‐ and TES‐evoked MEPs from the TA were smaller when swaying forward as compared to backward. Conclusions: The results indicated the presence of an enhanced cortical excitability because of the need to control for postural sway during normal standing. The increased cortical excitability was, however, unlikely to be involved in an on‐going control of postural sway, suggesting that postural sway is controlled at the spinal and/or subcortical levels.     

rTMS联合运动训练对运动皮质功能影响的研究

目的重复经颅磁刺激(rTMS)联合运动训练可有效提高肢体的运动能力。拟通过皮质静息期(CSP)记录的方法探讨rTMS联合运动训练对运动皮质功能的影响,进一步理解其提高运动能力的神经生理机制。方法募集了16例健康受试者,其中男性14例,女性2例;年龄23~31岁,平均年龄24.56岁。随机分为试验组和对照组,试验组进行为期14 d的rTMS联合运动训练,对照组仅进行14 d的运动训练。记录干预前后的CSP信号,并离线提取CSP中运动诱发电位(MEP)的幅值及潜伏期、CSP的持续时间。结果试验组左手MEP的幅值显著增加(z=3,P<0.05),潜伏期显著降低(z=25,P<0.05),CSP持续时间呈增加趋势,但是无统计学意义(z=6,P>0.05)。对照组左手MEP的幅值显著增加(z=4,P<0.05M),EP的潜伏期和CSP的持续时间均无显著变化(P>0.05)。两组受试者右手的MEP幅值、潜伏期和CSP持续时间的变化均无统计学意义(P>0.05)。结论rTMS联合运动训练同时调控了运动皮质兴奋和抑制性神经元的功能,它可能是rTMS联合运动训练提高肢体运动能力的重要原因。     

Corticospinal excitability during action observation in task-specific dystonia: a transcranial magnetic stimulation study

Observation of actions performed by other individuals activates the onlooker's motor system in a way similar to real movement execution. The functioning of this mechanism in the pathological domain is not clear yet. The aim of this study was to explore whether action observation activates the motor system of patients affected by a task-specific form of dystonia, such as writer's cramp. Transcranial magnetic stimulation was applied over the primary motor cortex and motor evoked potentials were recorded from hand (FDI and ADM) and forearm (FCR) muscles at baseline and during observation of actions (grasping and writing) or images. Writing actions could be performed with healthy or dystonic movement patterns. Results showed a highly specific and reversed pattern of activation in the FDI muscle of the two groups. Differences between the two writing conditions were significantly opposite in the two groups: control subjects had higher activation during observation of the dystonic compared to the healthy action, whereas in patients observation of the healthy writing led to higher activation than the dystonic writing. This opposite corticospinal modulation might be explained by a different self-attribution of the observed actions in the two groups.     

Probing the corticospinal link between the motor cortex and motoneurones: some neglected aspects of human motor cortical function

This review considers the operation of the corticospinal system in primates. There is a relatively widespread cortical area containing corticospinal outputs to a single muscle and thus a motoneurone pool receives corticospinal input from a wide region of the cortex. In addition, corticospinal cells themselves have divergent intraspinal branches which innervate more than one motoneuronal pool but the synergistic couplings involving the many hand muscles are likely to be more diverse than can be accommodated simply by fixed patterns of corticospinal divergence. Many studies using transcranial magnetic stimulation of the human motor cortex have highlighted the capacity of the cortex to modify its apparent excitability in response to altered afferent inputs, training and various pathologies. Studies using cortical stimulation at ‘very low’ intensities which elicit only short-latency suppression of the discharge of motor units have revealed that the rapidly conducting corticospinal axons (stimulated at higher intensities) drive motoneurones in normal voluntary contractions. There are also major non-linearities generated at a spinal level in the relation between corticospinal output and the output from the motoneurone pool. For example, recent studies have revealed that the efficacy of the human corticospinal connection with motoneurones undergoes activity-dependent changes which influence the size of voluntary contractions. Hence, corticospinal drives must be sculpted continuously to compensate for the changing functional efficacy of the descending systems which activate the motoneurones. This highlights the need for proprioceptive monitoring of movements to ensure their accurate execution.     

Establishing the definition and inter-rater reliability of cortical silent period calculation in subjects with focal hand dystonia and healthy controls

The purpose of this paper is to describe a clearly defined manual method for calculating cortical silent period (CSP) length that can be employed successfully and reliably by raters after minimal training in subjects with focal hand dystonia (FHD) and healthy subjects. A secondary purpose was to explore intra-subject variability of the CSP in subjects with FHD vs. healthy subjects. Two raters previously naïve to CSP identification and one experienced rater independently analyzed 170 CSP measurements collected in 6 subjects with focal hand dystonia (FHD) and 9 healthy subjects. Intraclass correlation coefficient (ICC) was calculated to quantify inter-rater reliability within the two groups of subjects. The relative variability of CSP in each group was calculated by the coefficient of variation (CV). Relative variation between raters within repeated measures of individual subjects was also quantified by CV. Reliability measures were as follows—mean of three raters: all subjects: ICC = 0.976; within healthy subjects: ICC = 0.965; in subjects with FHD: ICC = 0.956. The median within-subject variability for the healthy group was CV = 7.33% and in subjects with FHD:CV = 11.78%. The median variability of calculating individual subject CSP duration between raters was CV = 10.23% in subjects with dystonia and CV = 10.46% in healthy subjects. Manual calculation of CSP results in excellent reliability between raters of varied levels of experience. Healthy subjects display less variability in CSP. Despite greater variability, the CSP in impaired subjects can be reliably calculated across raters.     

Arm movement maps evoked by cortical magnetic stimulation in a robotic environment

Many neurological diseases result in a severe inability to reach for which there is no proven therapy. Promising new interventions to address reaching rehabilitation using robotic training devices are currently under investigation in clinical trials but the neural mechanisms that underlie these interventions are not understood. Transcranial magnetic stimulation (TMS) may be used to probe such mechanisms quickly and non-invasively, by mapping muscle and movement representations in the primary motor cortex (M1). Here we investigate movement maps in healthy young subjects at rest using TMS in the robotic environment, with the goal of determining the range of TMS accessible movements, as a starting point for the study of cortical plasticity in combination with robotic therapy. We systematically stimulated the left motor cortex of 14 normal volunteers while the right hand and forearm rested in the cradle of a two degree-of-freedom planar rehabilitation robot (IMT). Maps were created by applying 10 stimuli at each of nine locations (3×3 cm² grid) centered on the M1 movement hotspot for each subject, defined as the stimulation location that elicited robot cradle movements of the greatest distance. TMS-evoked movement kinematics were measured by the robotic encoders and ranged in magnitude from 0 to 3 cm. Movement maps varied by subject and by location within a subject. However, movements were very consistent within a single stimulation location for a given subject. Movement vectors remained relatively constant (limited to <90° section of the planar field) within some subjects across the entire map, while others covered a wider range of directions. This may be due to individual differences in cortical physiology or anatomy, resulting in a practical limit to the areas that are TMS-accessible. This study provides a baseline inventory of possible TMS-evoked arm movements in the robotic reaching trainer, and thus may provide a real-time, non-invasive platform for neurophysiology based evaluation and therapy in motor rehabilitation settings.     

Motor cortex excitability changes following a lesion in the posterior columns of the cervical spinal cord

We used transcranial magnetic stimulation (TMS) to explore if an impairment of central sensory function produced by an isolated lesion in the cervical posterior white columns would change motor cortex excitability. Cortical silent period duration was prolonged when compared with the control subjects, while central motor conduction and motor thresholds were in the normal limits. We first demonstrate that the involvement of the ascending proprioceptive sensory pathways in spinal cord diseases may have direct consequences on the activity of intracortical inhibitory interneuronal circuits. These findings further elucidate the role of afferent inputs in motor cortex reorganisation.     

Differential effect of linguistic and non-linguistic pen-holding tasks on motor cortex excitability

Writing and drawing are unique human activities. They are complex high-precision actions, which involve not only the motor system but also various cognitive systems, such as attention, short-term memory, action control, and language. In relation to motor control, the study of writing and drawing is of great interest as they provide insight in the interaction between motor control processes and the concurrent non-motor processes. Although sharing similar motor and mechanical demands, writing and drawing involve different levels of linguistic/semantic load and thus may be associated with different modulation of motor cortical excitability. Here, we have used transcranial magnetic stimulation to study separately activation of excitatory and inhibitory mechanisms of the motor cortex during performance of writing and drawing acts as well as during simple pen-squeezing task. While cortical excitatory mechanisms appeared to be saturated by the pure motor demands of the tasks, and thus not amenable to modulation by the tasks’ linguistic load, variation in cortical inhibitory activity was the main vehicle for differential modulation of motor cortical excitability by linguistic demands of the tasks. The results of this study highlight the importance of cortical inhibitory mechanisms in the physiology of higher cognitive activities. They also provide further evidence that the task specific modulation of the excitability of the motor cortex goes beyond motor complexity of the task and is also dependant on associated cognitive components.     

Diaphragmatic silent period to transcranial magnetic cortical stimulation for assessing cortical motor control of the diaphragm

This study was designed to determine whether a silent period could be elicited in the diaphragm electromyographic (EMG) activity by transcranial magnetic stimulation (TMS) of the motor cortex and, if so, to assess the influence of reflex or voluntary control of breathing on diaphragmatic cortical silent period (cSP). Diaphragmatic EMG activity was recorded in six healthy volunteers after motor cortex TMS triggered by the inspiratory flow peak and applied during forced inspiration (FI), voluntary hyperventilation (vHV) and reflex hyperventilation (rHV) to a CO(2) stimulus. Electrophysiological and respiratory parameters were studied, including diaphragmatic cSP duration and transdiaphragmatic pressure swing (DeltaPdi). A diaphragmatic cSP was found and correlated with DeltaPdi values. DeltaPdi and cSP duration were similar in the vHV and rHV conditions but were significantly increased during FI. This study established for the first time the existence of a diaphragmatic cSP to motor cortex TMS. The diaphragmatic cSP duration depended on the magnitude of the respiratory effort, as assessed by DeltaPdi, but not on the mechanism (volitional or reflex) of diaphragm activation.     

Changes in presumed motor cortical activity during fatiguing muscle contraction in humans

Aim: Changes in sensory information from active muscles accompany fatiguing exercise and the force-generating capacity deteriorates. The central motor commands therefore must adjust depending on the task performed. Muscle potentials evoked by transcranial magnetic stimulation (TMS) change during the course of fatiguing muscle activity, which demonstrates activity changes in cortical or spinal networks during fatiguing exercise. Here, we investigate cortical mechanisms that are actively involved in driving the contracting muscles. Methods: During a sustained submaximal contraction (30% of maximal voluntary contraction) of the elbow flexor muscles we applied TMS over the motor cortex. At an intensity below motor threshold, TMS reduced the ongoing muscle activity in biceps brachii. This reduction appears as a suppression at short latency of the stimulus-triggered average of rectified electromyographic (EMG) activity. The magnitude of the suppression was evaluated relative to the mean EMG activity during the 50 ms prior to the cortical stimulus. Results: During the first 2 min of the fatiguing muscle contraction the suppression was 10 ± 0.9% of the ongoing EMG activity. At 2 min prior to task failure the suppression had reached 16 ± 2.1%. In control experiments without fatigue we did not find a similar increase in suppression with increasing levels of ongoing EMG activity. Conclusion: Using a form of TMS which reduces cortical output to motor neurones (and disfacilitates them), this study suggests that neuromuscular fatigue increases this disfacilitatory effect. This finding is consistent with an increase in the excitability of inhibitory circuits controlling corticospinal output.     

Expertise with pathological actions modulates a viewer's motor system

Brain mechanisms for action understanding rely on matching the observed actions into the viewer's motor system. Health professionals, who treat patients affected by movement disorders as dystonia, frequently see hyperkinetic action patterns characterized by an overflow of muscle co-contractions. To avert an overload of the motor system during observation of those actions, they might need to look at dystonic motor symptoms in a cool, detached way. To investigate whether visual expertise about atypical movement kinematics influences the viewer's motor system, we applied transcranial magnetic stimulation to clinicians and to naive subjects, while they observed handwriting actions performed with two different kinematics: fluent and non-fluent. Crucially, the latter movement pattern was easily recognized by the clinicians as a typical expression of writer's cramp, whereas it was unknown to the naive subjects. Results showed that clinicians had similar corticospinal activation during observation of dystonic and healthy writings, whereas naive subjects were hyper-activated during observation of dystonic movements. Hyper-activation was selective for the muscles directly involved in the dystonic co-contractions and inversely correlated with subjective movement fluency scores, hinting at a fine-tuned association between the breakdown of observed movement fluency and corticospinal activation. These findings suggest that observation of unusual pathological actions differently modulates the viewer's motor system, depending on knowledge, visual expertise, and ability in recognizing suboptimal movement kinematics.     

重复经颅磁刺激联合针刺治疗脑梗死后吞咽障碍对吞咽功能及皮质兴奋性的影响

探讨重复经颅磁刺激（rTMS）联合针刺治疗脑梗死后吞咽障碍对吞咽功能及皮质兴奋性的影响。方法:选取64例脑梗死后吞咽障碍患者,随机分为对照组和治疗组,各32例。对照组予以假rTMS联合针刺治疗,治疗组予以rTMS联合针刺治疗。比较治疗后两组患者洼田试验等级、功能性经口摄食量表（FOIS）和渗漏-误吸量表（PAS）评分、表面肌电图信号（sEMG）（最大振幅和吞咽时限）、神经功能缺损评分（NIHSS）、神经元特异性烯醇化酶（NSE）水平以及治疗期间的不良反应情况。结果:治疗后,两组洼田饮水试验等级均有改善,且治疗组洼田饮水试验等级优于对照组（P<0.05）。两组FOIS评分高于治疗前,且PAS评分低于治疗前（P<0.05）;治疗组FOIS评分高于对照组,且PAS评分低于对照组（P<0.05）。两组sEMG最大振幅高于治疗前,且吞咽时限低于治疗前（P<0.05）;治疗组sEMG最大振幅高于对照组,且吞咽时限低于对照组（P<0.05）。两组NIHSS评分和NSE水平低于治疗前,治疗组NIHSS评分和NSE水平低于对照组（P<0.05）。治疗期间,两组无明显不良反应。结论:rTMS联合针刺治疗脑梗死后吞咽障碍可以改善吞咽功能,提高皮质兴奋性,促进神经功能恢复,安全性好,值得临床应用。     

Altered motor cortex excitability in tinnitus patients: a hint at crossmodal plasticity

Idiopathic tinnitus is a frequent and often debilitating auditory phantom perception of largely unknown pathological conditions. In electrophysiological and functional neuroimaging studies, affected subjects have shown excessive spontaneous activity in the central auditory system. To further investigate the underlying central nervous component, we assessed motor cortex excitability in 19 patients with chronic tinnitus by means of transcranial magnetic stimulation (TMS). When results were compared with data from 19 healthy controls matched for age and sex, we found significantly enhanced intracortical facilitation in tinnitus patients. These findings parallel excitability changes after limb amputation and experimental deafferentation. Our results give further support to crossmodal interactions involving neuroplastic changes in some forms of tinnitus and may help to better understand mechanisms of maladaptive cortical reorganisation involved in phantom perceptions.     

Antiepileptic drugs and cortical excitability: a study with repetitive transcranial stimulation

Repetitive transcranial magnetic stimulation (rTMS) delivered at various intensities and frequencies excites cortical motor areas. Trains of stimuli (at 5 Hz frequency, and suprathreshold intensity) progressively increase the size of muscle evoked potentials (MEPs) and the duration of the cortical silent period (CSP) in normal subjects. The aim of this study was to evaluate the effect of the antiepileptic drugs carbamazepine, gabapentin, and topiramate on cortical excitability variables tested with rTMS. We tested the changes in motor threshold, MEP size and CSP duration evoked by focal rTMS in 23 patients with neuropathic pain before and after a 1-week course of treatment with carbamazepine, gabapentin, topiramate and placebo. None of the three antiepileptic drugs changed the resting or active magnetic and electrical motor threshold. Antiepileptic treatment, but not placebo, abolished the normal rTMS-induced facilitation of MEPs, but left the progressive lengthening of the CSP during the rTMS train unchanged. Our results suggest that carbamazepine, gabapentin and topiramate modulate intracortical excitability by acting selectively on excitatory interneurons.     

Changes in corticospinal motor excitability induced by non-motor linguistic tasks

The excitability of the corticospinal motor pathways to transcranial magnetic stimulation (TMS) can be differentially modulated by a variety of motor tasks. However, there is emerging evidence that linguistic tasks may alter excitability of the corticospinal motor pathways also. In this study we evaluated the effect of several movement-free, low-level linguistic processes involved in reading and writing on the excitability of the bilateral corticospinal motor pathways in a group of right-handed subjects. The study included two series of tasks, visual searching/matching and imaginal writing/drawing. The tasks were designed to roughly correspond with elemental aspects of the reading and writing, grapheme recognition and grapheme generation, respectively. Each task series included separate blocks with different task targets: letters, digits, semantically easy-to-code (i.e. geometric) shapes, and semantically hard-to-code shapes, as well as control blocks with no task. During task performance, TMS was delivered randomly over the hand area of either the left or right motor cortex and the modulation of the excitability of the corticospinal motor pathways was measured bilaterally through changes of the size of the motor-evoked potential (MEP) induced in the relaxed right and left first dorsal interosseous (FDI) muscles. We found that the size of the MEP in hand muscles increased during visual searching/matching tasks, particularly when targets were letters or geometric shapes, and the increase was significant for the dominant hand (left hemisphere) only. No such consistent effects were seen across subjects during imaginal tasks. This study provides evidence that even the performance of certain low-level linguistic tasks can modulate the excitability of the corticospinal motor pathways, particularly those originating from the left (dominant) hemisphere, despite the absence of overt motor activity. Moreover, in the light of the recently increased awareness of the role of "mirror neurons" in perception, the results suggest that activation of motor circuits used in generation of the written output may be an essential part of the perception of the written material as well. Understanding the patterns of task-dependent changes in excitability of the corticospinal motor pathways will provide insights into the organisation of central nervous system functional networks involved in linguistic processes, and may also be useful for future development of novel approaches to rehabilitation therapy of linguistic and motor functions.     

奥卡西平对癫痫患者运动皮质兴奋性的影响

目的：利用经颅磁刺激（transcranial magnetic stimulation, TMS）技术来研究奥卡西平（oxcarbazepine, OXC）对部分性癫痫患者运动皮质兴奋性的影响，并与卡马西平(carbamazepine, CBZ)的作用相比较。方法：对38例头颅MRI正常的部分性癫痫患者和20例正常对照进行磁刺激，并记录双侧大脑的静息期运动皮质阈值(rest motor threshold, rMT)、运动诱发电位波幅（motor evoked potential amplitude，MEP amplitude）、皮质潜伏期(cortical latency, CL)和中枢传导时间（central motor conduction time, CMCT）。癫痫组中18例给予OXC治疗，20例给予CBZ治疗，在治疗后第2周末、第4周末分别给予TMS。结果： 癫痫组38例治疗前可能致痫灶同侧大脑rMT高于对侧大脑，但差异无显著(P>0.05)。奥卡西平组可能致痫灶同侧大脑rMT在第2周末和第4周末均明显高于治疗前(P<0.05)，卡马西平组可能致痫灶同侧大脑rMT仅在第4周末时高于治疗前(P<0.05)。癫痫组治疗前后同侧大脑MEP amplitude、CL和CMCT差别均无显著，两侧大脑半球间比较差别也无显著。结论： 头颅MRI正常的部分性癫痫患者可能致痫灶所在半球和对侧半球的大脑皮质兴奋性可能存在差异，OXC和CBZ均能降低运动皮质兴奋性，可能机制为细胞膜钠离子通道阻滞。 TMS是从电生理角度研究大脑皮质兴奋性的可靠辅助工具。