Churchland Mark M, Shenoy Krishna V
Department of Electrical Engineering and Neurosciences Program, 330 Serra Mall, Stanford University, Stanford CA 94305-4075, USA.
J Neurophysiol. 2007 Jan;97(1):348-59. doi: 10.1152/jn.00808.2006. Epub 2006 Sep 27.
We tested the hypothesis that delay-period activity in premotor cortex is essential to movement preparation. During a delayed-reach task, we used subthreshold intracortical microstimulation to disrupt putative "preparatory" activity. Microstimulation led to a highly specific increase in reach reaction time. Effects were largest when activity was disrupted around the time of the go cue. Earlier disruptions, which presumably allowed movement preparation time to recover, had only a weak impact. Furthermore, saccadic reaction time showed little or no increase. Finally, microstimulation of nearby primary motor cortex, even when slightly suprathreshold, had little effect on reach reaction time. These findings provide the first evidence, of a causal and temporally specific nature, that activity in premotor cortex is fundamental to movement preparation. Furthermore, although reaction times were increased, the movements themselves were essentially unperturbed. This supports the suggestion that movement preparation is an active and actively monitored process and that movement can be delayed until inaccuracies are repaired. These results are readily interpreted in the context of the recently developed optimal-subspace hypothesis.
运动前皮层中的延迟期活动对于运动准备至关重要。在延迟伸手任务中，我们使用阈下皮层内微刺激来干扰假定的“准备性”活动。微刺激导致伸手反应时间显著增加。当在执行信号出现前后干扰活动时，影响最大。较早的干扰可能使运动准备时间得以恢复，其影响则很微弱。此外，扫视反应时间几乎没有增加或根本没有增加。最后，即使是略高于阈值的对附近初级运动皮层的微刺激，对伸手反应时间也几乎没有影响。这些发现提供了首个具有因果关系和时间特异性的证据，即运动前皮层中的活动对于运动准备至关重要。此外，虽然反应时间增加了，但运动本身基本未受干扰。这支持了如下观点：运动准备是一个主动且受到积极监测的过程，并且运动可以延迟至误差得到修正。这些结果在最近提出的最优子空间假设的背景下很容易得到解释。
