Target-, limb-, and context-dependent neural activity in the cingulate and supplementary motor areas of the monkey
Target-, limb-, and context-dependent neural activity in the cingulate and supplementary motor areas of the monkey
复制标题
DOI：
10.1007/s00221-004-1895-0
复制
发表时间：
2004-10-01
影响因子：
2
通讯作者：
Backus, DA
中科院分区：
文献类型：
--
作者：
Crutcher, MD;Russo, GS;Backus, DA
与其他皮质运动区相比，扣带运动区（CMA）在视觉引导到达中的作用知之甚少。为了研究到达过程中尾侧CMA（CMAc）的层次作用，我们记录了CMAc中神经元的活动，并与补充运动区（SMA）进行了比较，同时猴子执行了一项指令延迟任务，该任务要求它使用二维（2D）操纵杆运动将光标定位在计算机屏幕上的视觉目标上。通过周期性地反转操纵杆的运动方向和光标的运动方向之间的关系，将猴子的手臂运动方向与视觉目标的方向分离。对特定肢体运动方向反应最大的神经元（无论目标位置如何）被归类为肢体依赖性神经元，而对特定目标方向反应最大的神经元（无论肢体运动方向如何）被归类为目标依赖性神经元。神经元的活动是定向的两个视觉映射条件之一和非定向或不活跃的其他被归类为上下文相关的。在延迟期（准备活动; CMAc，17%; SMA，31%）和运动执行期间（CMAc，49%，SMA，48%），在CMAc和SMA中观察到肢体依赖性活动比目标依赖性活动更频繁。在CMAc（11%）和SMA适当（8%）中，具有准备活动的神经元的适度百分比是靶点依赖性的，并且两个区域中的神经元的相似百分比表现出靶点依赖性运动活动（CMAc，8%; SMA，10%）。令人惊讶的发现是，这两个区域中的神经元在任务的准备阶段（CMAc，72%; SMA，61%）或运动阶段（CMAc，43%，SMA 42%）表现出非常大比例的上下文依赖性活动。这些结果表明，在CMAc和SMA的神经活动可以直接表示运动方向，无论是在肢体为中心或目标为中心的坐标。CMAc和SMA中存在目标依赖性活动，表明两者都参与了视觉目标信息转化为适当的运动命令。在壳核、SMA、CMAc、背侧和腹侧运动前皮质以及初级运动皮质中发现了靶点依赖性活动。这表明，视觉引导达到所需的视觉转换是由一个分布式网络的互联运动区。然而，大比例的神经元与上下文相关的活动表明，虽然CMAc和SMA可能发挥作用的视觉转换的目标信息到运动参数，他们的活动不仅仅是编码参数的运动，因为他们在这个过程中的参与是高度条件依赖性的。
Very little is known about the role of the cingulate motor area (CMA) in visually guided reaching compared to other cortical motor areas. To investigate the hierarchical role of the caudal CMA (CMAc) during reaching we recorded the activity of neurons in CMAc in comparison to the supplementary motor area proper (SMA) while a monkey performed an instructed delay task that required it to position a cursor over visual targets on a computer screen using two-dimensional (2D) joystick movements. The direction of the monkey's arm movement was dissociated from the direction of the visual target by periodically reversing the relationship between the direction of movement of the joystick and that of the cursor. Neurons that responded maximally with a particular limb movement direction regardless of target location were classified as limb-dependent, whereas neurons that responded maximally to a particular target direction regardless of the direction of limb movement were classified as target-dependent. Neurons whose activity was directional in one of the two visuomotor mapping conditions and non-directional or inactive in the other were categorized as context-dependent. Limb-dependent activity was observed more frequently than target-dependent activity in both CMAc and SMA proper during both the delay period (preparatory activity; CMAc, 17%; SMA, 31%) and during movement execution (CMAc, 49%, SMA, 48%). A modest percentage of neurons with preparatory activity were target-dependent in both CMAc (11%) and SMA proper (8%) and a similar percentage of neurons in both areas demonstrated target-dependent, movement activity (CMAc, 8%; SMA, 10%). The surprising finding was that a very large percentage of neurons in both areas displayed context-dependent activity either during the preparatory (CMAc, 72%; SMA, 61%) or movement (CMAc, 43%, SMA 42%) epochs of the task. These results show that neural activity in both CMAc and SMA can directly represent movement direction in either limb-centered or target-centered coordinates. The presence of target-dependent activity in CMAc, as well as SMA, suggests that both are involved in the transformation of visual target information into appropriate motor commands. Target-dependent activity has been found in the putamen, SMA, CMAc, dorsal and ventral premotor cortex, as well as primary motor cortex. This indicates that the visuomotor transformations required for visually guided reaching are carried out by a distributed network of interconnected motor areas. The large proportion of neurons with context-dependent activity suggests, however, that while both CMAc and SMA may play a role in the visuomotor transformation of target information into movement parameters, their activity is not solely coding parameters of movement, since their involvement in this process is highly condition-dependent.