Evolution of intention for voluntary action

为了了解大脑皮层中多个区域在运动行为的认知控制中所起的作用，人们对亚人类灵长类动物进行了一系列的实验研究。主要研究方向为动作意图的产生机制和运动行为的认知控制机制。通过在执行计划动作时检查皮层区域的细胞活动，出现了以下发现。(1)背侧运动前皮层的外侧部分，已知接收视觉和体感输入，是神经元检索有关目标和身体部位的信息的位置，而随后的活动指定计划的动作。(2)我们发现腹侧运动前皮层的细胞主要反映信息检索过程。另一方面，背侧运动前皮层的细胞更多地代表整合空间目标和肢体使用信息的过程，并随后计划采取“行动”。这种活动在内侧运动区少见。(3)扣带运动区吻侧部分参与运动选择奖励信息的加工。(4)背外侧前额叶皮层细胞在分类水平的行为规划中发挥作用，这一认知水平比规划个体序列所需的认知水平更为复杂。(5)另一方面，dl-PF中的细胞参与检索和保存有关事件时间序列的信息，以规划随后的运动行为。(6)研究发现，下顶叶细胞反映被试自身所采取的动作数量，从而为选择下一个动作提供信息。

To understand the role played by multiple areas in the cerebral cortex on cognitive control of motor behavior, a series of experimental studies have been performed using subhuman primates. The research interest was focused on mechanisms for generation of intention for action and for the cognitive control of motor behavior. By examining cellular activity in cortical areas during performance of planned actions, the following findings emerged. (1) The lateral sector of the dorsal premotor cortex, known to receive both visual and somatosensory input, is the site where neurons retrieve information about both the target and the body part, while subsequent activity specifies the planned action. (2) We found that cells in the ventral premotor cortex primarily reflect the process of information retrieval. On the other hand, cells in the dorsal premotor cortex more often represent the process of integrating the spatial-target and limb-use information, and subsequently of planning an 'action' to take. Such activity was infrequent in medial motor areas. (3) The rostral part of the cingulate motor areas plays a part in processing the reward information for motor selection. (4) Cells in the dorsolateral prefrontal cortex play a role in behavioral planning at the level of categorization, a cognitive level more complex than required for planning individual sequences. (5) On the other hand, cells in the dl-PF take part in retrieving and holding information about the temporal sequence of events for planning subsequent motor behavior. (6) Cells in the inferior parietal lobe are found to reflect the number of actions taken by the subject itself, thereby providing information to select a next action.