Deficit of hand preshaping after muscimol injection in monkey parietal cortex.

In order to assess the functional role of the parietal hand movement region, the anterior part of the lateral bank of the intraparietal sulcus (IPS), area AIP, in the visual guidance of hand grasping, we reversibly inactivated several parts of this area with microinjections of Muscimol in a monkey trained to grasp objects of different shapes, sizes and orientations. During the local inactivation, some of the skilled patterns of finger movements were disrupted in the contralateral hand, due to the lack of preshaping to adjust the finger posture to the object; however, no major deficits in visual reaching were observed. The results suggest that area AIP plays a crucial role in the visual guidance of goal-directed hand movements.