PARIETAL CORTEX AND SPATIAL-POSTURAL TRANSFORMATION DURING ARM MOVEMENTS

Parietal cortex and spatial-postural transformation during arm-movemen ts. J. Neurophysiol. 79: 478-482, 1998. cells in the parietal motor ar eas 5, MIP, and 7b have spatially tuned activity during movements. Les ions, however, do not disrupt visual reaching or learned nonspatial mo vement selection, The role of such parietal cells in sensorimotor coor dinate transformations is unclear. The present experiment investigates whether the parietal motor areas are concerned with the following: I) the transformation between the desired position in space of the hand a nd the limb's postural configuration during movement and 2) interjoint coordination. Six macaque monkeys were trained to reach in the dark. Spatial-postural transformations assume a simple form in the absence o f vision and so may be most easily studied when animals reach in the d ark. A lesion was placed in the parietal cortex that included areas 5, MIP, and 7b of three macaques. The simple relation between hand posit ion and limb postural configuration seen in controls was disrupted aft er the lesion. The intercoordination of movements of the hand with tho se of the rest of the arm was also affected. The lesion did not affect the range or velocity of joint movements or the curvature of the hand 's trajectory. The cell activity in parietal areas 5, MIP, and 7b may not be essential for the transformation between retinocentric represen tation of the target and shoulder centered representations of the desi red position of the hand. but it is essential for both the subsequent transformation between desired hand position and the postural configur ation of the arm and for interjoint integration.