Institute of Neuroinformatics, University of Zürich and ETH Zürich, CH-8057 Zürich, Switzerland.
J Neurosci. 2010 Nov 10;30(45):15175-84. doi: 10.1523/JNEUROSCI.3343-10.2010.
Hand grasping requires the transformation of sensory signals to hand movements. Neurons in area F5 (ventral premotor cortex) represent specific grasp movements (e.g., precision grip) as well as object features like orientation, and are involved in movement preparation and execution. Here, we examined how F5 neurons represent context-dependent grasping actions in macaques. We used a delayed grasping task in which animals grasped a handle either with a power or a precision grip depending on context information. Additionally, object orientation was varied to investigate how visual object features are integrated with context information. In 420 neurons from two animals, object orientation and grip type were equally encoded during the instruction epoch (27% and 26% of all cells, respectively). While orientation representation dropped during movement execution, grip type representation increased (20% vs 43%). According to tuning onset and offset, we classified neurons as sensory, sensorimotor, or motor. Grip type tuning was predominantly sensorimotor (28%) or motor (25%), whereas orientation-tuned cells were mainly sensory (11%) or sensorimotor (15%) and often also represented grip type (86%). Conversely, only 44% of grip-type tuned cells were also orientation-tuned. Furthermore, we found marked differences in the incidence of preferred conditions (power vs precision grips and middle vs extreme orientations) and in the anatomical distribution of the various cell classes. These results reveal important differences in how grip type and object orientation is processed in F5 and suggest that anatomically and functionally separable cell classes collaborate to generate hand grasping commands.
手的抓握需要将感觉信号转化为手部运动。F5 区（腹侧前运动皮层）的神经元既可以代表特定的抓握动作（如精确抓握），也可以代表物体的特征，如方向，并参与运动的准备和执行。在这里，我们研究了 F5 神经元如何在猕猴中表示上下文相关的抓握动作。我们使用了延迟抓握任务，在该任务中，动物根据上下文信息用力量或精确抓握来抓握手柄。此外，还改变了物体的方向，以研究视觉物体特征如何与上下文信息相结合。在两只猴子的 420 个神经元中，在指令阶段，物体方向和握力类型同样被编码（分别占所有细胞的 27%和 26%）。虽然在运动执行期间，方向的表示减少了，但握力类型的表示增加了（20%对 43%）。根据调谐的起始和结束，我们将神经元分类为感觉、感觉运动或运动神经元。握力类型的调谐主要是感觉运动（28%）或运动（25%），而方向调谐的细胞主要是感觉（11%）或感觉运动（15%），并且经常也代表握力类型（86%）。相反，只有 44%的握力类型调谐细胞也对方向调谐。此外，我们发现偏好条件（力量对精确抓握和中间对极端方向）的发生率和各种细胞类别的解剖分布存在显著差异。这些结果揭示了 F5 中处理握力类型和物体方向的重要差异，并表明解剖学上和功能上可分离的细胞类群共同协作产生手抓握命令。
