Monitoring of motor pathways during brain stem surgery: What we have achieved and what we still miss?

Intraoperative neurophysiological monitoring (IOM) has established itself as one of the paths by which modern neurosurgery can improve surgical results while minimizing morbidity. IOM consists of both monitoring (continuous "on-line" assessment of the functional integrity of neural pathways) and mapping (functional identification and preservation of anatomically ambiguous nervous tissue) techniques. In posterior-fossa and brainstem surgery, mapping techniques can be used to identify - and therefore preserve - cranial nerves, their motor nuclei and corticospinal or corticobulbar pathways. Similarly, free-running electromyography (EMG) and muscle motor-evoked potential (mMEP) monitoring can continuously assess the functional integrity of these pathways during surgery. Mapping of the corticospinal tract, at the level of the cerebral peduncle as well as mapping of the VII, IX-X and XII cranial nerve motor nuclei on the floor of the fourth ventricle, is of great value to identify "safe entry-zones" into the brainstem. Mapping techniques allow recognizing anatomical landmarks such as the facial colliculus, the hypoglosseal and glossopharyngeal triangles on the floor of the fourth ventricle, even when normal anatomy is distorted by a tumor. On the basis of neurophysiological mapping, specific patterns of motor cranial nuclei displacement can be recognized. However, brainstem mapping cannot detect injury to the supranuclear tracts originating in the motor cortex and ending on the cranial nerve motor nuclei. Therefore, monitoring techniques should be used. Standard techniques for continuously assessing the functional integrity of motor cranial nerves traditionally rely on the evaluation of spontaneous free-running EMG in muscles innervated by motor cranial nerves. Although several criteria have been proposed to identify those EMG activity patterns that are suspicious for nerve injury, the terminology remains somewhat confusing and convincing data regarding a clinical correlation between EMG activity and clinical outcome are still lacking. Transcranial mMEPs are also currently used during posterior-fossa surgery and principles of MEP monitoring to assess the functional integrity of motor pathways are similar to those used in brain and spinal-cord surgery. Recently, current concepts in muscle MEP monitoring have been extended to the monitoring of motor cranial nerves. So-called "corticobulbar mMEPs" can be used to monitor the functional integrity of corticobulbar tracts from the cortex through the cranial motor nuclei and to the muscle innervated by cranial nerves. Methodology for this purpose has appeared in the literature only recently and mostly with regards to the VII cranial nerve monitoring. Nevertheless, this technique has not yet been standardized and some limitations still exist. In particular, with regards to the preservation of the swallowing and coughing reflexes, available intraoperative techniques are insufficient to provide reliable prognostic data since only the efferent arc of the reflex can be tested.     

Intraoperative neurophysiologic monitoring for intramedullary spinal-cord tumor surgery

During resection of intramedullary spinal-cord tumors intraoperative neurophysiological monitoring has become a true surgical technology. Motor evoked potentials are the most important modality for this purpose. Its use requires neurophysiological expertise from the surgeon, and a monitoring team in place able to handle the necessary equipment. Motor potentials are evoked by transcranial electrical motor cortex stimulation. A "single stimulus technique" evokes D-waves recorded from the spinal cord. The "multipulse (or train) stimulation technique" evokes electromyographic responses in peripheral muscles. These are optimally recorded from the thenar, hypothenar, tibialis anterior, and flexor hallucis brevis muscles, which are known to have strong pyramidal innervation. D-wave monitoring looks primarily at the peak-to-peak amplitude. When monitoring muscle MEPs, the presence or absence of the response irrespective of stimulation intensity is the important parameter. Preparations for neurophysiological monitoring fit quite well into a neurosurgical operating room environment. Recording and interpretation of MEPs is fast and straightforward. Pre- and postoperative clinical motor findings correlate with intraoperative MEP results. Thus correct prediction of the clinical status at a given time during surgery is possible with a very high certainty. The sensitivity of muscle MEPs for postoperative motor deficits is nearly 100%, its specificity is about 90%. Thus MEP data indeed reflect the clinical "reality". Present and stable recordings document intact motor pathways and allow the surgeon to confidently proceed with a tumor resection. Loss of muscle MEPs and/or decrease of the D-wave amplitude constitutes a "window of warning". It reflects a pattern of MEP change indicating a reversible injury to the essential motor pathways. Using this information, the surgical strategy can be adapted before irreversible neurological damage is caused by the surgical manipulation. Such adaptation comprises simply waiting for the recordings to spontaneously improve again, irrigating with warm saline solution to wash out blocking potassium. Other measures include the elevation of mean arterial pressure to improve local perfusion. Even staged resection can be considered if intraoperative measures do not sufficiently improve the recordings.     

Subdural Recording of Bereitschaftspotential Is Useful for Functional Mapping of the Epileptogenic Motor Area:

Summary: A 26-year-old man with intractable focal motor seizure beginning with tonic contraction of the left orbicularis oculi muscle had prolonged EEG monitoring with subdural grid electrodes placed over the right perirolandic cortex. Electrical stimulation of the cortex with implanted subdural electrodes showed a relatively low threshold for afterdischarges (ADS) but could not disclose the motor area for the left upper face where or near where the epileptogenic area was expected to be present. Bereitschaftspotential recorded from the subdural electrodes in association with self-paced voluntary blink (eyelid closing) disclosed the motor area specifically related to voluntary movements of the left upper face, which was most likely buried in the sulcus. This observation suggests that recording of Bereitschaftspotential from subdural electrodes is useful for mapping the motor cortex, especially in patients with focal motor seizure with low threshold for ADS to electric stimuli.     

Motor cortex stimulation for levodopa-resistant akinesia: case report.

We treated a patient with levodopa-resistant akinesia with motor cortex stimulation (MCS), and she showed dramatic improvement more than 1 year. On admission, the patient presented severe akinesia and gait disturbance without tremor and rigidity, and did not respond to levodopa test. The patient was suspected pure akinesia and progressive supranuclear palsy. First, high-frequency rTMS of primary motor cortex was examined, and showed the dramatic improvement. Next, chronic subdural electrodes were implanted over the motor cortex bilaterally. One year after surgery, the Unified Parkinson's Disease Rating Scale had improved remarkably, and she could walk four times faster than before. The H2 15O PET study showed a significant increase of rCBF in the left SMA and right dorsolateral prefrontal cortex after bilateral MCS. MCS may be an alternative treatment for patients with akinesia, including those with PD, and particularly for levodopa-resistant patients, who respond well to rTMS.     

运动皮质电刺激术治疗顽固性神经病理性疼痛

目的研究运动皮质电刺激术（motor cortex stimulation,MCS）治疗顽固性神经病理性疼痛的临床应用。方法脑卒中后疼痛9例,脊髓损伤后疼痛3例,幻肢痛2例。均行MCS治疗,同期植入刺激电极和脉冲发生器。采用视觉模拟疼痛评分（VAS）评价疗效。结果术后疼痛均不同程度减轻,1个月以内镇痛疗效较满意,VAS评分较术前显著降低（P〈0．01）。随访1。5年．多数病人镇痛效果出现波动,调整刺激参数后仍能获得镇痛疗效,疼痛较术前减轻10％～90％,脑卒中后疼痛的长期疗效要好于脊髓损伤后疼痛和幻肢痛。结论MCS是治疗神经病理性疼痛的一种新方法,具有疗效肯定、可调节等优点,术后刺激参数的调整对疗效的影响至关重要。     

Repetition and variation in motor practice: A review of neural correlates

Random practice results in more effective motor learning than either constant or blocked practice. Recent studies have investigated the effects of practice schedules at the neurophysiological level. This study aims to conduct a literature review of the following issues: (a) the differential involvement of premotor areas, the primary motor cortex, the dorsolateral prefrontal cortex and the posterior parietal cortex in different types of practice; (b) changes in the participation of these areas throughout practice; and (c) the degree of support that current neurophysiological findings offer to strengthen the behavioral proposition that distinct cognitive processes are generated by different practice schedules. Data from 10 studies that investigated associations between practice structures and neurobiological substrates were analyzed. The participation of the indicated areas was found to depend on practice structure and varied during the learning process. Greater cognitive engagement was associated with random practice. In conclusion, distinct neural processes are engendered by different practice conditions. The integration of behavioral and neurophysiological findings promotes a more comprehensive view of the phenomenon.     

运动皮层电刺激治疗丘脑痛3例并文献复习

目的 探讨运动皮层电刺激治疗丘脑痛的安全性及有效性。方法 回顾性分析2017年1月至2018年12月首都医科大学三博脑科医院采用运动皮层电刺激治疗的3例丘脑梗死或出血后导致的对侧肢体疼痛的临床资料。结果 术前表现为持续性疼痛，间断性加重，疼痛性质为烧灼样或刀割样，伴肢体发紧，视觉模拟量表（VAS）评分9~10分，均服用阿司匹林、布洛芬、曲马多等多种镇痛药物及抗抑郁药物，效果不佳。术后VAS评分2~3分，下降超过70%。术后无癫痫等并发症，四肢肌力同术前，右侧躯体及肢体疼痛较术前有明显改善。术后随访6~12个月，病人反映疼痛缓解程度较前有所降低，增大刺激电压后，疼痛再次缓解。结论 运动皮层电刺激治疗丘脑痛安全有效，并能改善病人的生活质量，具有创伤小、并发症少等优点。     

Subdural motor cortex stimulation in Parkinson's disease does not modify movement-related rCBF pattern.

There has been some evidence that electrical stimulation of the primary motor cortex (MCS) may relieve motor symptoms of Parkinson's disease (PD). This surgical technique is being studied as alternative for PD patients who are considered poor candidates for deep brain stimulation (DBS) of subthalamic nucleus (STN). In 4 PD patients with unilateral MCS, we used [(15)O] H(2)O positron emission tomography to measure changes in regional cerebral blood flow (rCBF) while testing motor performance with a joystick motor task during different stimulation frequencies, OFF-condition, 50 and 130 Hz. We found that different stimulation settings did neither improve performance on joystick task nor modify the pattern of movement-related rCBF. Similarly, no changes were observed in UPDRS motor score between Off and On stimulation while off medication. We conclude that while MCS may be a simpler and safer surgical procedure than DBS of STN, it failed to provide evidence of clear effect on motor performance and movement-related activation pattern in patients with advanced PD.     

Transcranial and direct cortical stimulation for motor evoked potential monitoring in intracerebral aneurysm surgery

STUDY AIM: To analyse the parallel use of transcranial electrical stimulation (TES) and direct cortical stimulation (DCS) for eliciting muscle motor evoked potentials (MMEPs) in intracranial aneurysm surgery; to correlate permanent or transient TES- and/or DCS-MMEP changes with surgical maneuvers and clinical motor outcome. PATIENTS AND METHODS: TES and DCS were intraoperatively performed in 108 patients (51.5+/-14.7 years); MMEPs were obtained in muscles belonging to the vascular territory of interest. Monopolar, anodal stimulation was achieved with a train of five stimuli consisting of an individual pulse width of 0.5ms, an interstimulus interval of 4ms, a train repetition rate of 0.5-2Hz, and maximum stimulation intensities up to 200mA (TES) versus 25mA (DCS). RESULTS: In 95/108 (88%) patients, no changes in MMEPs occurred and none of these patients suffered a permanent severe motor deficit. In 14/108 (12%) patients, we observed nine (64%) temporary changes, four (29%) permanent deteriorations and one (7%) permanent MMEP loss. Out of 14 MMEP changes, nine (64%) occurred with TES, compared to 13 (93%) with DCS (Fishers'p=0.165). Parallel changes in TES- and DCS-MMEPs occurred in 8/14 patients (57%), in which case a permanent loss was always followed by a permanent severe motor deficit. Sixty-seven percent of all permanent changes occurred with DCS-MMEPs, compared to 33% with TES-MMEPs (p=0.567, NS). DISCUSSION AND CONCLUSIONS: In aneurysm surgery, provided that close-to-motor-threshold stimulation and the most focal stimulating electrode montage are used, TES- and DCS-MMEPs do not differ in their capacity to detect an impending lesion of the motor cortex or its efferent pathways. TES stimulation can cause significant muscular contraction during surgery, potentially disrupting the operating surgeon. DCS maintains the singular advantage of stimulating a very focal and superficial motor cortex stimulation that does not result in patient movement.     

Repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex and cortical excitability in patients with major depressive disorder

Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex is a relatively non-invasive technique with putative therapeutic effects in major depression. However, the exact neurophysiological basis of these effects needs further clarification. Therefore, we studied the impact of ten daily sessions of left, dorsolateral prefrontal rTMS on motor cortical excitability, as revealed by transcranial magnetic stimulation-elicited motor-evoked potentials in 30 patients. As compared to the non-responders, responders (33%) showed changes in parameters pointing towards a reduced cortical excitability. These results suggest that repetitive transcranial magnetic stimulation of the dorsolateral, prefrontal cortex may have inhibitory effects on motor cortical neuronal excitability in patients with major depressive disorder. Furthermore, measurement of motor cortical excitability may be a useful tool for investigating and monitoring inhibitory brain effects of antidepressant stimulation techniques like rTMS.     

Motor cortex plasticity can indicate vulnerability to motor fluctuation and high L-DOPA need in drug-naïve Parkinson's disease

IntroductionMotor cortex plasticity is reported to be decreased in Parkinson's disease in studies which pooled patients in various stages of the disease. Whether the early decrease in plasticity is related to the motor signs or is linked to the future development of motor complications of treatment is unclear. The aim of the study was to test if motor cortex plasticity and its cerebellar modulation are impaired in treatment-naïve Parkinson's disease, are related to the motor signs of the disease and predict occurrence of motor complications of treatment.MethodsTwenty-nine denovo patients with Parkinson's disease were longitudinally assessed for motor complications for four years. Using transcranial magnetic stimulation, the plasticity of the motor cortex and its cerebellar modulation were measured (response to paired-associative stimulation alone or preceded by 2 active cerebellar stimulation protocols), both in the untreated state and after a single dose of L-DOPA. Twenty-six matched, healthy volunteers were tested, only without L-DOPA.ResultsPatients and healthy controls had similar proportions of responders and non-responders to plasticity induction. In the untreated state, the more efficient was the cerebellar modulation of motor cortex plasticity, the lower were the bradykinesia and rigidity scores. The extent of the individual plastic response to paired associative stimulation could indicate a vulnerability to develop early motor fluctuation but not dyskinesia.ConclusionsMeasuring motor cortex plasticity in denovo Parkinson's disease could be a neurophysiological parameter that may help identify patients with greater propensity for early motor fluctuations.     

Safety aspects of transcranial direct current stimulation concerning healthy subjects and patients

Cortical excitability changes induced by tDCS and revealed by TMS, are increasingly being used as an index of neuronal plasticity in the human cortex. The aim of this paper is to summarize the partially adverse effects of 567 tDCS sessions over motor and non-motor cortical areas (occipital, temporal, parietal) from the last 2 years, on work performed in our laboratories. One-hundred and two of our subjects who participated in our tDCS studies completed a questionnaire. The questionnaire contained rating scales regarding the presence and severity of headache, difficulties in concentrating, acute mood changes, visual perceptual changes and any discomforting sensation like pain, tingling, itching or burning under the electrodes, during and after tDCS. Participants were healthy subjects (75.5%), migraine patients (8.8%), post-stroke patients (5.9%) and tinnitus patients (9.8%). During tDCS a mild tingling sensation was the most common reported adverse effect (70.6%), moderate fatigue was felt by 35.3% of the subjects, whereas a light itching sensation under the stimulation electrodes occurred in 30.4% of cases. After tDCS headache (11.8%), nausea (2.9%) and insomnia (0.98%) were reported, but fairly infrequently. In addition, the incidence of the itching sensation (p=0.02) and the intensity of tingling sensation (p=0.02) were significantly higher during tDCS in the group of the healthy subjects, in comparison to patients; whereas the occurrence of headache was significantly higher in the patient group (p=0.03) after the stimulation. Our results suggest that tDCS applied to motor and non-motor areas according to the present tDCS safety guidelines, is associated with relatively minor adverse effects in healthy humans and patients with varying neurological disorders.     

Cortical mechanisms involved in visuomotor coordination during precision walking

Goal-directed locomotion, in particular in situations where there is a need to step over or around obstacles, is largely guided by visual information. To negotiate an obstacle successfully, subjects must first plan how to perform the movement and then must execute that plan. In cats, this information must also be stored and used to guide the hindlimbs, which are moved in the absence of direct visual input. Experiments in cats have shown that the motor cortex makes an important contribution to the execution of gait modifications and is involved both in specifying limb trajectory and, when necessary, where the paw will be placed. We suggest that, in both situations, subpopulations of pyramidal tract neurons in the motor cortex act to regulate the duration, level and timing of small groups of synergistic muscles, active at different times during the gait modification. However, the available evidence suggests that the motor cortex plays little role in the planning of these gait modifications. Instead, recent work suggests that the posterior parietal cortex (PPC) may contribute to this function. In agreement with this proposal, we have found that lesions to this structure lead to errors in forelimb placement in front of an advancing obstacle and may produce deficits in forelimb-hindlimb coordination. Single-unit recordings from neurons in the PPC support a role for the PPC in these two aspects of visually guided locomotion and further show that the signal in this structure might be limb-independent.     

Motor Cortex Stimulation Suppresses Cortical Responses to Noxious Hindpaw Stimulation After Spinal Cord Lesion in Rats

BackgroundMotor cortex stimulation (MCS) is a potentially effective treatment for chronic neuropathic pain. The neural mechanisms underlying the reduction of hyperalgesia and allodynia after MCS are not completely understood.ObjectiveTo investigate the neural mechanisms responsible for analgesic effects after MCS. We test the hypothesis that MCS attenuates evoked blood oxygen-level dependent signals in cortical areas involved in nociceptive processing in an animal model of chronic neuropathic pain.MethodsWe used adult female Sprague–Dawley rats (n = 10) that received unilateral electrolytic lesions of the right spinal cord at the level of C6 (SCL animals). In these animals, we performed magnetic resonance imaging (fMRI) experiments to study the analgesic effects of MCS. On the day of fMRI experiment, 14 days after spinal cord lesion, the animals were anesthetized and epidural bipolar platinum electrodes were placed above the left primary motor cortex. Two 10-min sessions of fMRI were performed before and after a session of MCS (50 μA, 50 Hz, 300 μs, for 30 min). During each fMRI session, the right hindpaw was electrically stimulated (noxious stimulation: 5 mA, 5 Hz, 3 ms) using a block design of 20 s stimulation off and 20 s stimulation on. A general linear model-based statistical parametric analysis was used to analyze whole brain activation maps. Region of interest (ROI) analysis and paired t-test were used to compare changes in activation before and after MCS in these ROI.ResultsMCS suppressed evoked blood oxygen dependent signals significantly (Family-wise error corrected P < 0.05) and bilaterally in 2 areas heavily implicated in nociceptive processing. These areas consisted of the primary somatosensory cortex and the prefrontal cortex.ConclusionsThese findings suggest that, in animals with SCL, MCS attenuates hypersensitivity by suppressing activity in the primary somatosensory cortex and prefrontal cortex.     

Mechanisms controlling motor output to a transfer hand after learning a sequential pinch force skill with the opposite hand

ObjectiveTraining to perform a serial reaction-time task (procedural motor learning) with one hand results in performance improvements in the untrained as well as in the trained hand, a phenomenon referred to as intermanual transfer. The aim of this study was to investigate the neurophysiological changes associated with intermanual transfer associated with learning to perform an eminently different task involving fine force control within the primary motor cortex (M1). We hypothesized that intermanual transfer of learning such a task would reveal intracortical changes within M1.MethodsSpeed (time to complete each sequence) and accuracy (% of accuracy errors) of motor performance were measured in both hands before and after right (dominant) hand practice. Transcranial magnetic stimulation (TMS) was used to characterize recruitment curves (RC), short intracortical inhibition (SICI), intracortical facilitation (ICF) and interhemispheric inhibition (IHI) from the left to the right M1.ResultsPractice resulted in significant improvements in both speed and accuracy in the right trained hand and in the left untrained hand. RC increased in the left M1, SICI decreased in both M1s, and IHI from the left to the right M1 decreased. No changes were identified in ICF nor in RC in the right M1.ConclusionsOur results suggest that some neurophysiological mechanisms operating in the M1 controlling performance of an untrained hand may contribute to optimize the procedure for selecting and implementing correct pinch force levels.SignificanceThese results raise the hypothesis of a contribution of modulation of SICI and IHI, or an interaction between both to intermanual transfer after learning a sequential pinch force task.     

rTMS reveals premotor cortex dysfunction in frontal lobe epilepsy

PURPOSE: Studies of motor cortex excitability provided evidence that focal epilepsies may alter the excitability of cortical areas distant from the epileptogenic zone. In order to explore this hypothesis we studied the functional connectivity between premotor and motor cortex in seven patients with frontal lobe epilepsy and seizure onset zone outside the premotor or motor cortex. METHODS: Low-frequency subthreshold repetitive transcranial magnetic stimulation was applied to the premotor cortex and its impact on motor cortex excitability was measured by the amplitude of motor-evoked potentials in response to direct suprathreshold stimulation of the motor cortex. RESULTS: Stimulation of the premotor cortex of the non-epileptogenic hemisphere resulted in a progressive and significant inhibition of the motor cortex as evidenced by a reduction of motor evoked potential amplitude. On the other hand, stimulation of the premotor cortex of the epileptogenic hemisphere failed to inhibit the motor cortex. The reduced inhibition of the motor cortex by remote areas was additionally supported by the significantly shorter cortical silent periods obtained after stimulation of the motor cortex of the epileptogenic hemisphere. CONCLUSION: These results show that the functional connectivity between premotor and motor cortex or motor cortex interneuronal excitability is impaired in the epileptogenic hemisphere in frontal lobe epilepsy while it is normal in the nonepileptogenic hemisphere.     

Spinal arteriovenous malformations: Clinical and neurophysiological findings

Eighteen patients with dural arteriovenous fistulas or intradural arteriovenous malformations underwent clinical and neurophysiological examination. Bladder disturbances, pain, sensory abnormalities and involvement of both upper and lower motor neurons were commonly observed. Abnormal findings were obtained both in electromyography (11/18) and somatosensory evoked potentials (16/18). The motor evoked potentials were abnormal in all but one patient and showed a prolonged central (n = 14) or peripheral motor conduction time (n = 6). In three cases both values were prolonged. The results of nerve conduction studies in the patients with prolonged peripheral motor conduction times were normal. These neurophysiological findings may indicate root involvement in some patients, probably due to venous congestion and consequent hypoxia, as there were no signs of root compression on neuroradiological evaluation in any of these six patients. Motor evoked potentials may provide an additional clue to the diagnosis, although patients with spinal stenosis or motor neuron disease may present with similar findings.     

A direct demonstration of cortical LTP in humans: a combined TMS/EEG study

Repetitive transcranial magnetic stimulation (rTMS) is increasingly being used to promote cortical reorganization, under the assumption that it can induce long-term potentiation (LTP) of neural responses. This assumption is supported by several lines of indirect evidence. For example, rTMS of motor cortex can induce a potentiation of muscle motor evoked potentials that outlasts the stimulation by several minutes. In animal models, a direct demonstration of LTP is typically obtained by high-frequency electrical stimulation coupled with local field recordings of population responses. In this study, we exploited a new approach based on combined rTMS/high-density electroencephalography (hd-EEG) to obtain direct, noninvasive evidence for LTP in humans. Cortical responses to single TMS pulses were measured with hd-EEG before and after applying rTMS to motor cortex (5Hz, 1500 pulses). The results demonstrate that, after rTMS, EEG responses at latencies of 15-55ms were significantly potentiated. A topographic analysis revealed that this potentiation was significant at EEG electrodes located bilaterally over premotor cortex. Thus, these findings provide a direct demonstration in humans of LTP induced by rTMS.     

Electrical stimulation of primary motor cortex within the central sulcus for intractable neuropathic pain.

OBJECTIVE: To assess the pain-relieving effects of motor cortex electrical stimulation (MCS) within the central sulcus and the predictive factors retrospectively. METHODS: Thirty-four patients with intractable neuropathic pain underwent MCS; 19 patients had cerebral lesions, and 15 had non-cerebral lesions. In selected 12 patients, test electrodes were implanted within the central sulcus and on the precentral gyrus. Twelve patients received both MCS and repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex. RESULTS: Pain reduction of > or =50% was observed in 12 of 32 (36%) patients with > or =12 months follow-ups (2 patients were excluded because of short follow-up). In 10 of the 12 patients who received test electrodes within the central sulcus and on the precentral gyrus, the optimal stimulation was MCS within the central sulcus. In 4 of these (40%) patients, positive effects were maintained at follow-ups. The pain reduction of rTMS significantly correlated with that of MCS during test stimulation. CONCLUSIONS: The test stimulation within the central sulcus was more effective than that of the precentral gyrus. In the selected patients, chronic stimulation within the central sulcus did not significantly improve long-term results. SIGNIFICANCE: The present findings suggest that an intra-central sulcus is one of the favorable targets for MCS.     

What is “mirror” in the premotor cortex? A review

We review the findings of 24 fMRI studies examining activations in the premotor cortex (Brodmann's areas 6 and 44) during passive observation of actions. We found that such activations regularly occurred. Looking for functional differentiation in the premotor cortex, we found that one parameter was associated with systematic differences in location: this was the presence or absence of targets. Observing biological actions with a physical target, compared to a visual control showing no action at all, consistently activated the ventral premotor cortex (BA 6), and did so significantly more than observing target-less actions (with the same control). In contrast, the activity in BA 44 ("Broca's area") was not modulated by the presence or absence of targets. We propose that the ventral precentral gyrus, and not BA 44, shares the visual properties of "mirror" neurons found in area F5 of the macaque brain.