Gomez J E, Fu Q, Flament D, Ebner T J
Department of Neuroscience, 421 Lions Research Building, University of Minnesota, 2001 Sixth St S.E., Minneapolis, MN 55455, USA.
Eur J Neurosci. 2000 Oct;12(10):3748-60. doi: 10.1046/j.1460-9568.2000.00232.x.
The endpoint accuracy of a reaching movement strongly affects kinematics, particularly during the final phases of movement. However, where and how accuracy is represented in the central nervous system remains unknown. In this study, the discharge of 150 neurons located primarily in the dorsal premotor cortex (PMd), were recorded from monkeys performing an instructed delay, centre-out reaching task in which movement direction and target size were systematically varied. Linear regression analyses were used to assess the dependence of movement kinematics and cell discharge on target direction, size and tangential velocity (i.e. speed). The speed and timing of the movement were dependent on both direction and target size. Initially direction was the dominant predictor whilst target size became more important as the hand reached the target. A temporal multiple linear regression analysis found significant correlations with target size in 99 of 150 cells. The discharge of 134 cells was directionally tuned and 83 cells modulated with mean speed. Significant correlations of discharge with target size occurred throughout the task as did correlations with direction. However, correlations with direction preferentially occurred early in the task, prior to movement onset, whilst correlations with target size tended to occur late, well after movement onset. This temporal dependency of the firing in relationship to target direction and size mirrored that observed for the kinematics. We conclude that the discharge of PMd cells is highly correlated with the accuracy requirement of the movement. The timing of the correlations suggest that accuracy information is available for the planning and for the on-line control of endpoint accuracy.
伸手动作的终点准确性会强烈影响运动学，尤其是在动作的最后阶段。然而，在中枢神经系统中准确性是在哪里以及如何表征的仍不清楚。在本研究中，主要记录了150个位于背侧运动前皮层（PMd）的神经元的放电情况，这些神经元来自执行指令延迟、中心向外伸手任务的猴子，在该任务中，运动方向和目标大小被系统地改变。线性回归分析用于评估运动学和细胞放电对目标方向、大小和切向速度（即速度）的依赖性。运动的速度和时间取决于方向和目标大小。最初，方向是主要的预测因素，而当手接近目标时，目标大小变得更加重要。一项时间多元线性回归分析发现，150个细胞中有99个与目标大小存在显著相关性。134个细胞的放电具有方向选择性，83个细胞的放电随平均速度而调制。在整个任务过程中，放电与目标大小以及与方向的相关性都很显著。然而，与方向的相关性优先出现在任务早期，在动作开始之前，而与目标大小的相关性往往出现在后期，在动作开始之后很久。这种放电与目标方向和大小之间的时间依赖性反映了在运动学中观察到的情况。我们得出结论，PMd细胞的放电与动作的准确性要求高度相关。相关性出现的时间表明，准确性信息可用于终点准确性的规划和在线控制。
