PHYSIOLOGICAL ANALYSIS OF VOLUNTARY MOVEMENT

该项目的目标是更多地了解正常人和自愿运动障碍患者的运动控制，如帕金森氏症、小脑性共济失调、中风偏瘫和肌张力障碍。我们使用的工具包括临床神经生理学方法，如脑电、肌电和经颅磁刺激，以及正电子发射断层扫描和功能磁共振成像的神经成像。目前，该科正在进行的项目包括帕金森氏症运动迟缓的分析、偏瘫恢复的研究以及肌张力障碍的生理学研究。该科的一个主要科学目标是了解并可能影响患有先天性或获得性中枢神经系统损伤的患者的皮质重组。一种多模式方法(PET神经成像和功能磁共振、EEG和经颅磁刺激)正被用来确定个体卒中患者功能性脑电地形图的长期重组模式。对皮质下病变患者的数据分析表明，皮质活动和兴奋性模式的重组取决于病变在内囊内的位置。我们通过评估皮质-肌肉功能耦合的强度来检验同侧感觉运动皮质在卒中康复中是否起到一定的作用。同侧感觉运动皮质的EEG和EMG之间没有明显的一致性，表明同侧皮质-肌肉直接联系没有出现或增强。为了测试使用脑电进行宏观相干性测量的有效性，我们使用对象检测任务进行了一项实验。左右半球必须相互通信，才能构成横跨视觉中线的单一视觉刺激的神经关联。在刺激后117-373ms，大脑半球间的一致性在8-12赫兹范围内显著增加。这种短暂的连贯性增加不会发生在没有意义的物体上，或者当检测到熟悉的物体失败时，这表明一定程度的神经同步是视觉感知的先决条件。评估手部肌张力障碍患者的空间辨别力。与正常对照组相比，肌张力障碍患者的空间频率检测阈值升高，定位误差更大。这种空间辨别力的异常，加上时间辨别力的异常，支持了感觉系统功能障碍可能与肌张力障碍的发病机制有关的假设。在正常受试者中评估与自主肌肉放松相关的脑电功率变化。它与脑电的去同步化模式有关，其大小和皮质地形图与自愿收缩相似，但随后的脑电同步化程度更高。这表明放松是大脑的一个活跃过程。为了解释为什么人们更有可能向后摔倒而不是向前摔倒，我们研究了被平移推动装置干扰的受试者。我们发现，平衡的极限可以通过身体质心的位置和速度来预测。跌倒倾向的不对称性是由于功能性足部长度的不对称性。我们使用与事件相关的功能磁共振成像设计，扫描了正常受试者，当他们用右手食指进行内部和外部触发运动时。在前辅助运动区内，内触发动作的激活度显著高于内触发运动，而在辅助运动区本身内，内、外触发任务之间没有显著差异。这表明前区在自我启动运动中起主导作用。

The goal of this project is to learn more about the control of movement in normal humans and in patients with voluntary movement disorders such as Parkinson's disease, cerebellar ataxia, hemiplegia from stroke and dystonia. The tools we use include clinical neurophysiological methods such as electroencephalography, electromyography, and transcranial magnetic stimulation and neuroimaging with positron emission tomography and functional magnetic resonance imaging. Currently active projects in the Section include analysis of the bradykinesia in Parkinson's disease, studies of recovery from hemiplegia, and the physiology of dystonia. One major scientific target of the Branch is to understand and possibly influence cortical reorganization in patients with congenital or acquired lesions of the central nervous system. A multi-modality approach (neuroimaging with PET and functional MRI, EEG, and transcranial magnetic stimulation) is being used to determine patterns of long-term reorganization of functional brain topography in individual stroke patients. Analysis of data from patients with subcortical lesions indicated that the reorganization of the cortical activity and excitability patterns depends on the site of the lesion within the internal capsule. We tested whether the ipsilateral sensorimotor cortex plays some role in stroke recovery by evaluating the strength of cortico-muscular functional coupling. There was no significant coherence between EEG over the ipsilateral sensorimotor cortex and EMG indicating no emergence or enhancement of the ipsilateral direct cortico-muscular connection. To test the validity of macroscopic coherence measurements using EEG, we performed an experiment using an object detection task. Right and left hemispheres must communicate with each other to constitute the neural correlate of a unitary visual stimulus spanning the visual midline. The interhemispheric coherence revealed a significant increase in 8-12 Hz at 117-373 ms following the target stimuli. This transient coherence increase did not occur with meaningless objects or when the detection of the familiar object failed suggesting that a certain level of neural synchrony is a prerequisite for visual awareness. Spatial discrimination was evaluated in patients with hand dystonia. Compared to normal matched controls, dystonia patients have increased threshold for detection of spatial frequency and a larger localization error. This abnormality in spatial discrimination, together with abnormal temporal discrimination, support the hypothesis that a dysfunction of the sensory system may be relevant to the pathogenesis of dystonia. EEG power changes associated with voluntary muscle relaxation were evaluated in normal subjects. It is associated with a pattern of EEG desynchronization of similar magnitude and cortical topography to that associated with voluntary contraction, but with a subsequent greater EEG synchronization. This indicates that relaxation is an active process of the brain. In order to explain why people more likely to fall backward than forward, we studied subjects perturbed by a translational pushing device. We found that limitations to balance can be predicted by position and velocity of the center of mass of the body. Asymmetry of the tendency to fall is due to the asymmetry of the functional foot length. We scanned, using an event-related fMRI design, normal subjects while they were performing internally and externally triggered movements with their right index finger. Within the pre-supplementary motor area the activation was significantly higher for internally triggered movements, while within the supplementary motor area proper there was no significant difference between internally and externally triggered task. This suggests a dominant role of the anterior region in the self-initiation of movements.