Department of Psychology, University of Western Ontario, London, Ontario, Canada.
J Neurophysiol. 2011 Nov;106(5):2248-63. doi: 10.1152/jn.01069.2010. Epub 2011 Jul 27.
Reach-to-grasp actions require coordination of different segments of the upper limbs. Previous studies have examined the neural substrates of arm transport and hand grip components of such actions; however, a third component has been largely neglected: the orientation of the wrist and hand appropriately for the object. Here we used functional magnetic resonance imaging adaptation (fMRA) to investigate human brain areas involved in processing hand orientation during grasping movements. Participants used the dominant right hand to grasp a rod with the four fingers opposing the thumb or to reach and touch the rod with the knuckles without visual feedback. In a control condition, participants passively viewed the rod. Trials in a slow event-related design consisted of two sequential stimuli in which the rod orientation changed (requiring a change in wrist posture while grasping but not reaching or looking) or remained the same. We found reduced activation, that is, adaptation, in superior parieto-occipital cortex (SPOC) when the object was repeatedly grasped with the same orientation. In contrast, there was no adaptation when reaching or looking at an object in the same orientation, suggesting that hand orientation, rather than object orientation, was the critical factor. These results agree with recent neurophysiological research showing that a parieto-occipital area of macaque (V6A) is modulated by hand orientation during reach-to-grasp movements. We suggest that the human dorsomedial stream, like that in the macaque, plays a key role in processing hand orientation in reach-to-grasp movements.
抓握动作需要协调上肢的不同部位。先前的研究已经研究了手臂运输和此类动作的手抓握组件的神经基础；然而，第三个组件在很大程度上被忽视了：手腕和手的方向适合物体。在这里，我们使用功能磁共振成像适应（fMRI）来研究涉及抓握运动中手方向处理的人类大脑区域。参与者使用惯用右手用四个手指与拇指相对来抓握一根杆，或者用指关节接触而不看杆。在对照条件下，参与者被动地观看杆。在慢事件相关设计的试验中，有两个连续的刺激，其中杆的方向发生了变化（需要改变抓握时的手腕姿势，但不需要伸手或看）或保持不变。当物体以相同的方向重复抓握时，我们发现上顶枕皮层（SPOC）的激活减少，即适应。相比之下，当以相同的方向伸手或看物体时，没有适应，这表明手的方向而不是物体的方向是关键因素。这些结果与最近的神经生理学研究一致，该研究表明猕猴的顶枕后区（V6A）在伸手抓握运动中被手的方向调制。我们认为，人类背内侧流与猕猴一样，在手伸向抓握运动中处理手的方向起着关键作用。
