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如何在伸手和伸手抓取行为中协调近端和远端成分。心理物理学研究已经确定，伸展和抓握运动的特点是手臂、手腕和手指之间的不同协调模式，并假设存在协调机制，将上肢的这些部分暂时耦合起来。然而，这些时间协调模式背后的神经基质是未知的。我们最近发现，在非人类灵长类动物中，局部场电位（LFP）记录的行波活动在初级运动皮层（MI）、背前运动皮层（PMd）和腹前运动皮层（PMv）之间水平传播。这些传播波是由β频率范围（即15-40 Hz）的振荡活动介导的，主要沿着MI和PMv的倒尾轴和PMd的中侧轴传播。考虑到这些区域沿这些轴的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手和抓握过程中近端和远端成分的协调。特别是，鼻侧MI、尾侧PMv和内侧PMd与肩部和肘关节的近端肢体节段有关，而MI、PMv和PMd的尾侧、吻侧和外侧区域分别与手腕和手指的远端肢体节段有关。因此，上臂的近端到远端序列表征了许多行为，包括伸手抓握的加速阶段，这是由MI中从喙端到尾端方向、PMv中从尾端到喙端方向和PMd中从内侧到外侧方向的波传播来信号的。相反，远端到近端协调模式应该是

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.