Nakayama Yoshihisa, Yamagata Tomoko, Hoshi Eiji
Frontal Lobe Function Project, Tokyo Metropolitan Institute of Medical Science, Kamikitazawa 2-1-6, Setagaya-ku, Tokyo, 156-8506, Japan.
Tamagawa University Brain Science Institute, Machida, Tokyo, Japan.
Eur J Neurosci. 2016 Jun;43(12):1569-89. doi: 10.1111/ejn.13254. Epub 2016 May 10.
The dorsal premotor cortex residing in the dorsolateral aspect of area 6 is a rostrocaudally elongated area that is rostral to the primary motor cortex (M1) and caudal to the prefrontal cortex. This region, which is subdivided into rostral [pre-dorsal premotor cortex (pre-PMd)] and caudal [dorsal premotor cortex proper (PMd)] components, probably plays a central role in planning and executing actions to achieve a behavioural goal. In the present study, we investigated the functional specializations of the pre-PMd, PMd, and M1, because the synthesis of the specific functions performed by each area is considered to be essential. Neurons were recorded while monkeys performed a conditional visuo-goal task designed to include separate processes for determining a behavioural goal (reaching towards a right or left potential target) on the basis of visual object instructions, specifying actions (direction of reaching) to be performed on the basis of the goal, and preparing and executing the action. Neurons in the pre-PMd and PMd retrieved and maintained behavioural goals without encoding the visual features of the visual object instructions, and subsequently specified the actions by multiplexing the goals with the locations of the targets. Furthermore, PMd and M1 neurons played a major role in representing the action during movement preparation and execution, whereas the contribution of the pre-PMd progressively decreased as the time of the actual execution of the movement approached. These findings revealed that the multiple processing stages necessary for the realization of an action to accomplish a goal were implemented in an area-specific manner across a functional gradient from the pre-PMd to M1 that included the PMd as an intermediary.
位于6区背外侧的背侧运动前皮层是一个前后向拉长的区域,位于初级运动皮层(M1)的前方,前额叶皮层的后方。该区域可细分为前部[背侧运动前皮层前部(pre-PMd)]和后部[背侧运动前皮层本部(PMd)],可能在计划和执行实现行为目标的动作中起核心作用。在本研究中,我们研究了pre-PMd、PMd和M1的功能特化,因为每个区域执行的特定功能的综合被认为是必不可少的。在猴子执行一个条件视觉目标任务时记录神经元活动,该任务设计为包括基于视觉物体指令确定行为目标(伸向右侧或左侧潜在目标)、根据目标指定要执行的动作(伸手方向)以及准备和执行动作的单独过程。pre-PMd和PMd中的神经元检索并维持行为目标,而不编码视觉物体指令的视觉特征,随后通过将目标与目标位置复用指定动作。此外,PMd和M1神经元在运动准备和执行期间对动作的表征中起主要作用,而随着实际运动执行时间的临近,pre-PMd的贡献逐渐减少。这些发现表明,实现目标动作所需的多个处理阶段以区域特异性方式在从pre-PMd到M1的功能梯度上实现,其中包括PMd作为中间区域。