Coding of action by motor & premotor cortical ensembles

描述（由申请人提供）：该项目的目的是了解运动特征是如何在相互作用的运动皮质神经元中编码的。虽然以前的电生理学研究主要集中在单个运动皮质神经元的编码上，但很少有研究表明，从相互作用的神经元集合中产生的活动的时空模式是否编码了运动计划和执行的特征。为了验证这一假设，高密度电极阵列将长期植入初级运动皮层（MI）和背侧运动前皮层（PMd），当猴子用手臂执行复杂的视觉运动任务时，将同时记录100个单个单元。连续随机跟踪任务和阶跃随机跟踪任务非常适合研究神经编码，因为它们可以解除许多相关运动变量之间的统计依赖性，更彻底地采样运动空间，并减少非平稳性。正向和反向相关、信息论和解码方法将用于分析编码问题以及两个皮质区域之间的信息映射。本项目提出了两个具体目标。首先，将研究运动皮质集合的运动学和动力学调谐特性，并将其与不同行为背景下的单个神经元调谐功能进行比较。这些调节功能的稳定性将通过对手臂施加不同的外部负荷、改变行为模式（自由移动与等距运动）或改变前臂的姿势来检验。其次，它将确定运动皮质集合内的时空模式是否可以通过改变运动的时间动态和可预测性来引出。这项工作意义重大，因为它将阐明相互作用的皮层神经元群如何控制和协调复杂的运动，并将为理解其他皮层区域的神经元群如何代表其他高级功能提供重要的一步。此外，这项工作与神经运动假体的发展直接相关，瘫痪患者可以通过激活他们的皮层来控制外部设备。

DESCRIPTION (provided by applicant): The objective of this project is to understand what and how movement features are encoded in ensembles of interacting motor cortical neurons. Although previous electrophysiological research has focused on encoding in single motor cortical neurons, very little work has examined whether spatial-temporal patterns of activity emerging from ensembles of interacting neurons encode features of movement planning and execution. To test this hypothesis, high-density electrode arrays will be chronically implanted in primary motor cortex (MI) and dorsal premotor cortex (PMd) from which 100s of single units will be simultaneously recorded while monkeys perform complex visuo-motor tasks with the arm. A continuous random-tracking task and a step random-tracking task are ideally suited to investigate neural encoding because they uncouple the statistical dependencies among many of the relevant motor variables, more thoroughly sample the movement space, and reduce non-stationarities. Forward and reverse correlation, information-theoretic, and decoding methods will be used to analyze the encoding problem as well the information mapping between the two cortical areas. Two specific aims are proposed in this project. First, kinematic and kinetic tuning properties of motor cortical ensembles will be investigated and compared to single neuron tuning functions under different behavioral contexts. The stability of these tuning functions will be examined by applying different external loads to the arm, varying the behavioral mode (freely moving vs. isometric), or changing the posture of the forearm. Second, it will determined whether spatio-temporal patterns within motor cortical ensembles can be elicited by altering the temporal dynamics and predictability of the movement. This work is significant because it will elucidate how groups of interacting cortical neurons control and coordinate complex movements and will provide an important step in understanding how neuronal ensembles in other cortical areas represent other high-level functioning. In addition, this work has direct relevance towards the development of a neuro-motor prosthesis by which paralyzed patients may be able to control external devices by activating their cortex.