Coding of Action by Motor & Premotor Cortical Ensembles

描述(由申请人提供)：本项目的目标是了解多个运动皮质区域中相互作用的神经元集合如何协调伸手和伸手抓住行为中的近端和远端组件。心理物理学研究已经确定，伸手和抓握运动的特点是手臂、手腕和手指之间存在不同的协调模式，并假设存在协调机制，这些协调机制在时间上耦合上肢的这些部分。然而，这些时间协调模式背后的神经基础尚不清楚。我们最近从非人类灵长类动物的局部场电位(LFP)记录中发现了行波活动的存在，这种活动水平地传播到初级运动(MI)、背侧前运动(PMD)和腹侧前运动(PMV)皮质。这些传播波是由β频率范围(即15-40赫兹)的振荡活动所介导的，并且在MI和PMV中主要沿着吻尾轴传播，在PMD中主要沿着内侧轴传播。考虑到这些区域近端和远端运动表征的梯度，我们的工作假设是，这些波反映了上肢在伸展和握持过程中近端和远端组件的协调。特别是，肩部MI、尾部PMV和内侧PMD分别与肩部和肘部的近侧肢体节段相关，MI、PMV和PMD的尾部、吻侧和外侧区域分别与手腕和手指的远端肢体节段相关。因此，上臂近端到远端的序列特征包括伸展到抓握的加速期等许多行为，其信号是通过在MI中沿吻端到尾端方向传播，在PMV中沿尾端到吻端方向传播，在PMD中沿内侧方向传播。相反，远端到近端的协调模式应该是 与波在相反方向的传播有关。我们将1)确定这些传播波的特性是否与伸展和伸手抓住行为中肩部、肘部、手腕和手指的不同协调模式相关；2)通过行为约束和扰动在这些波特性和行为之间建立联系；3)确定多个单一单位活动是否反映与同一电极阵列上记录的LFP波一致的时空模式。为了实现这一点，高密度电极阵列将被长期植入MI、PMV和PMD中，从那里将同时记录100s的单个单位和局部场电位，而猴子在不同的三维位置伸手和抓住不同大小、形状和方向的物体。使用一组10个红外摄像机的数字光学跟踪系统将监测手臂和手在伸手抓握行为中的运动学，而肌电信号将测量手臂、手腕和手指外部肌肉的活动。将采用一套经典的和新的计算方法来表征使用LFP和多个单一单元测量的波浪活动的动力学。

DESCRIPTION (provided by applicant): The goal of this project is to understand how ensembles of interacting neurons in multiple motor cortical areas coordinate proximal and distal components in reaching and reach-to-grasp behavior. Psychophysical research has determined that reaching and prehensile movements are characterized by distinct coordination patterns among the arm, wrist, and fingers and has postulated the existence of coordination mechanisms that temporally couple these segments of the upper limb. However, the neural substrate underlying these temporal coordination patterns is unknown. We have recently discovered the existence of travelling wave activity as recorded from local field potential (LFP) recordings in non-human primates that propagates horizontally across primary motor (MI), dorsal premotor (PMd), and ventral premotor (PMv) cortices. These propagating waves are mediated by oscillatory activity in the beta frequency range (i.e. 15-40 Hz) and propagate primarily along a rostro-caudal axis in MI and PMv and a medio-lateral axis in PMd. Given the gradient in proximal and distal movement representations along these axes in these areas, our working hypothesis is that these waves reflect the coordination of proximal and distal components of the upper limb during reaching and prehension. In particular, rostral MI, caudal PMv, and medial PMd are associated with proximal limb segments of the shoulder and elbow and caudal, rostral, and lateral regions of MI, PMv, and PMd, respectively are associated with distal limb segments of the wrist and fingers. Therefore, the proximal-to-distal sequencing of the upper arm that characterizes many behaviors including the accelerative phase of reach-to-grasp is signaled by wave propagation in the rostral-to-caudal direction in MI, caudal-to-rostral direction in PMv, and medial-to-lateral direction in PMd. In contrast, distal-to-proximal coordination patterns should be associated with wave propagation in the opposite direction. We will 1) determine whether properties of these propagating waves correlate with distinct coordination patterns of the shoulder, elbow, wrist, and fingers during reach and reach- to-grasp behaviors; 2) establish a link between these wave properties and behavior via behavioral constraints and perturbations 3) determine whether multiple single unit activity reflects spatio-temporal patterns consistent with the LFP waves recorded on the same electrode arrays. To accomplish this, high-density electrode arrays will be chronically implanted in MI, PMv, and PMd from which 100s of single units and local field potentials will be simultaneously recorded while monkeys reach for and grasp objects of different sizes, shapes, and orientations in different three-dimensional locations. A digital optical tracking system using a set of ten infrared cameras will monitor the kinematics of the arm and hand during reach-to-grasp behavior and EMG signals will measure activity from arm, wrist, and extrinsic finger muscles. A set of classical and novel computational methods will be employed to characterize the dynamics of wave activity measured using LFPs and multiple single units.