PHYSIOLOGICAL ANALYSIS OF VOLUNTARY MOVEMENT

该项目的目标是更多地了解正常人和自主运动障碍患者的运动控制，如帕金森病、小脑性共济失调、中风引起的偏瘫和肌紧张性障碍。我们使用的工具包括临床神经生理学方法，如脑电图、肌电图、经颅磁刺激和正电子发射断层扫描和功能磁共振成像的神经成像。该科目前活跃的项目包括帕金森病运动迟缓的分析、偏瘫康复的研究和肌张力障碍的生理学。该分支的一个主要科学目标是了解并可能影响先天性或获得性中枢神经系统病变患者的皮层重组。一种多模式的方法（PET、功能性MRI、脑电图和经颅磁刺激的神经成像）被用于确定个体中风患者功能性脑地形的长期重组模式。对皮质下病变患者的数据分析表明，皮层活动和兴奋性模式的重组取决于内囊内病变的部位。我们通过评估皮质-肌肉功能耦合的强度来测试同侧感觉运动皮层是否在脑卒中恢复中起一定作用。同侧感觉运动皮层的脑电图与肌电图之间没有明显的一致性，表明同侧皮质-肌肉直接连接没有出现或增强。为了验证脑电宏观相干性测量的有效性，我们使用目标检测任务进行了实验。左右半球必须相互沟通，以构成跨越视觉中线的单一视觉刺激的神经关联。目标刺激后117 ~ 373 ms，脑内相干性在8 ~ 12 Hz范围内显著增加。这种短暂的相干性增加不会发生在无意义的物体上，也不会发生在对熟悉物体的检测失败时，这表明一定程度的神经同步是视觉意识的先决条件。评估了手肌张力障碍患者的空间辨别能力。与正常对照相比，肌张力障碍患者空间频率检测阈值升高，定位误差较大。这种空间辨别的异常，以及时间辨别的异常，支持了感觉系统功能障碍可能与肌张力障碍发病机制有关的假设。在正常受试者中评估与随意肌松弛相关的脑电图功率变化。它与脑电图去同步模式有关，其幅度和皮层地形与自发性收缩相关的脑电图去同步模式相似，但随后脑电图同步程度更高。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容易向后摔倒而不是向前摔倒，我们研究了受平移推装置干扰的受试者。我们发现平衡的限制可以通过身体质心的位置和速度来预测。不对称的跌倒倾向是由于不对称的脚的功能长度。我们使用与事件相关的功能磁共振成像（fMRI）设计，对正常受试者用右手食指进行内部和外部触发的运动进行扫描。在辅助运动前区域内，内部触发的运动的激活明显更高，而在辅助运动区域内，内部和外部触发的任务之间没有显著差异。这表明前部在运动的自我启动中起主导作用。

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.