Dipartimento di Fisiologia Umana e Generale, Università di Bologna, I-40126 Bologna, Italy.
J Neurosci. 2010 Nov 3;30(44):14773-85. doi: 10.1523/JNEUROSCI.2313-10.2010.
Reaching and grasping an object is an action that can be performed in light, as well as in darkness. Area V6A is a visuomotor area of the medial posterior parietal cortex involved in the control of reaching movements. It contains reaching neurons as well as neurons modulated by passive somatosensory and visual stimulations. In the present work we analyze the effect of visual feedback on reaching activity of V6A neurons. Three macaques were trained to execute reaching movements in two conditions: in darkness, where only the reaching target was visible, and in full light, where the monkey also saw its own moving arm and the environment. Approximately 85% of V6A neurons (127/149) were significantly related to the task in at least one of the two conditions. The majority of task-related cells (69%) showed reach-related activity in both visual conditions, some were modulated only in light (15%), while others only in dark (16%). The sight of the moving arm often changed dramatically the cell's response to arm movements. In some cases the reaching activity was enhanced and in others it was reduced or disappeared altogether. These neuronal properties may represent differences in the degree to which cells are influenced by feedback control versus feedforward movement planning. On average, reach-related modulations were stronger in light than in dark, a phenomenon similar to that observed in brain imaging experiments in the human medial posterior parietal cortex, a region likely homologous to macaque area V6A.
伸手抓握物体是一种可以在有光和无光的情况下完成的动作。V6A 区是内侧顶后皮质的一个运动视觉区域，参与控制伸手运动。它包含伸手神经元和由被动体感和视觉刺激调制的神经元。在本工作中，我们分析了视觉反馈对视运动神经元伸手活动的影响。三只猕猴接受训练，在两种条件下执行伸手运动：在黑暗中，只有伸手目标可见；在全光下，猕猴也可以看到自己移动的手臂和环境。大约 85%的 V6A 神经元（127/149）在至少一种视觉条件下与任务有显著的相关性。大多数与任务相关的细胞（69%）在两种视觉条件下都表现出与伸手相关的活动，有些只在光下（15%）被调制，而另一些只在暗（16%）下被调制。移动手臂的视觉常常极大地改变了细胞对手臂运动的反应。在某些情况下，伸手活动增强，而在其他情况下，它完全减少或消失。这些神经元特性可能代表了细胞受反馈控制和前馈运动规划影响的程度差异。平均而言，与伸手相关的调制在光下比在暗下更强，这一现象类似于人类内侧顶后皮质的脑成像实验中观察到的现象，该区域可能与猕猴的 V6A 区同源。
