Reina G A, Moran D W, Schwartz A B
The Neurosciences Institute, San Diego, California 92121, USA.
J Neurophysiol. 2001 Jun;85(6):2576-89. doi: 10.1152/jn.2001.85.6.2576.
Single-unit activity in area M1 was recorded in awake, behaving monkeys during a three-dimensional (3D) reaching task performed in a virtual reality environment. This study compares motor cortical discharge rate to both the hand's velocity and the arm's joint angular velocities. Hand velocity is considered a parameter of extrinsic space because it is measured in the Cartesian coordinate system of the monkey's workspace. Joint angular velocity is considered a parameter of intrinsic space because it is measured relative to adjacent arm/body segments. In the initial analysis, velocity was measured as the difference in hand position or joint posture between the beginning and ending of the reach. Cortical discharge rate was taken as the mean activity between these two times. This discharge rate was compared through a regression analysis to either an extrinsic-coordinate model based on the three components of hand velocity or to an intrinsic-coordinate model based on seven joint angular velocities. The model showed that velocities about four degrees-of-freedom (elbow flexion/extension, shoulder flexion/extension, shoulder internal/external rotation, and shoulder adduction/abduction) were those best represented in the sampled population of recorded activity. Patterns of activity recorded across the cortical population at each point in time throughout the task were used in a second analysis to predict the temporal profiles of joint angular velocity and hand velocity. The population of cortical units from area M1 matched the hand velocity and three of the four major joint angular velocities. However, shoulder adduction/abduction could not be predicted even though individual cells showed good correlation to movement on this axis. This was also the only major degree-of-freedom not well correlated to hand velocity, suggesting that the other apparent relations between joint angular velocity and neuronal activity may be due to intrinsic-extrinsic correlations inherent in reaching movements.
在虚拟现实环境中进行三维（3D）伸手任务时，对清醒、行为状态下的猴子的M1区单神经元活动进行了记录。本研究将运动皮层放电率与手部速度和手臂关节角速度进行了比较。手部速度被视为外在空间的一个参数，因为它是在猴子工作空间的笛卡尔坐标系中测量的。关节角速度被视为内在空间的一个参数，因为它是相对于相邻的手臂/身体节段进行测量的。在初始分析中，速度被测量为伸手开始和结束时手部位置或关节姿势的差异。皮层放电率被视为这两个时间点之间的平均活动。通过回归分析，将该放电率与基于手部速度三个分量的外在坐标模型或基于七个关节角速度的内在坐标模型进行比较。该模型表明，在记录活动的抽样群体中，约四个自由度（肘部屈伸、肩部屈伸、肩部内/外旋转以及肩部内收/外展）的速度得到了最佳体现。在整个任务的每个时间点，对整个皮层群体记录的活动模式进行了第二次分析，以预测关节角速度和手部速度的时间变化曲线。来自M1区的皮层神经元群体与手部速度以及四个主要关节角速度中的三个相匹配。然而，尽管单个细胞在该轴上与运动显示出良好的相关性，但肩部内收/外展却无法被预测。这也是唯一与手部速度相关性不佳的主要自由度，表明关节角速度与神经元活动之间的其他明显关系可能是由于伸手动作中固有的内在-外在相关性所致。
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