Fattori Patrizia, Breveglieri Rossella, Amoroso Katia, Galletti Claudio
Dipartimento di Fisiologia Umana e Generale, Università di Bologna, P.zza P.ta S. Donato 2, 40126 Bologna, Italy.
Eur J Neurosci. 2004 Nov;20(9):2457-66. doi: 10.1111/j.1460-9568.2004.03697.x.
In humans, the caudal pole of the superior parietal lobule is involved in the control of both reaching and grasping movements, whereas in monkey it is reported to be involved only in the control of reaching. Using single-unit recordings from trained macaque monkeys, we investigated whether area V6A, a visuomotor area located in the caudal part of the posterior parietal cortex, is involved in both components of prehension, the hand transport towards the visual target and the grip formation to secure the grasp. In Experiment 1, neural activity was recorded in V6A while two monkeys performed two instructed-delay reaching tasks (reach-to-point and reach-to-grasp) under controlled conditions in darkness. Fourty-five of 93 tested neurons (48%) were modulated during reach-to-point and 62% (52/84) during reach-to-grasp. In 63% of cells (51/81) neural activity was significantly different between reach-to-point and reach-to-grasp tasks, suggesting that grip formation could influence neural activity. In Experiment 2, two monkeys performed natural reach-to-grasp movements in fully lit environment; V6A neural activity and arm-hand movements were recorded by a digital camcorder and analysed frame-by-frame using a digital video technique. Thirty of the 58 tested neurons (52%) were modulated during natural prehension; about 30% of these neurons (8/30) were modulated only during the last phase of prehension, i.e. during finger flexion around the object to be grasped. This is the first direct demonstration that both reaching and grasping modulate neural activity in the caudal part of the posterior parietal cortex of the macaque. Our work suggests a strict functional homology between human and monkey superior parietal lobule.
在人类中，顶上小叶的尾极参与到达和抓握动作的控制，而在猴子中，据报道它仅参与到达动作的控制。我们利用对经过训练的猕猴进行单神经元记录，研究了位于后顶叶皮质尾部的视觉运动区域V6A是否参与抓握动作的两个组成部分，即手向视觉目标的移动以及为确保抓握而形成的抓握动作。在实验1中，当两只猴子在黑暗的受控条件下执行两项指令延迟到达任务（指向目标和抓握目标）时，记录了V6A区域的神经活动。在指向目标任务中，93个测试神经元中的45个（48%）被调制，在抓握目标任务中，84个中有62%（52个）被调制。在63%的细胞（81个中的51个）中，指向目标和抓握目标任务之间的神经活动存在显著差异，这表明抓握动作的形成可能会影响神经活动。在实验2中，两只猴子在完全明亮的环境中进行自然的抓握动作；用数码摄像机记录V6A区域的神经活动和手臂手部动作，并使用数字视频技术逐帧分析。58个测试神经元中的30个（52%）在自然抓握过程中被调制；其中约30%的神经元（8/30）仅在抓握动作的最后阶段被调制，即在手指围绕要抓握的物体弯曲时。这是首次直接证明到达和抓握动作均能调制猕猴后顶叶皮质尾部的神经活动。我们的研究表明人类和猴子的顶上小叶之间存在严格的功能同源性。
