Motor Psychophysics

The motor plan for an arm-reaching movement can be defined in a variety of frames of reference. This article reviews the behavioral and electrophysiological evidence that this movement vector is initially defined in a retinocentric frame of reference (parietal reach region) then subsequently remapped into frames of reference more closely aligned with arm posture (area 5 and primary motor cortex). These coordinate transformations are facilitated by the remapping of proprioceptively derived hand location from arm-fixed to retinocentric coordinates, and may facilitate visually mediated, online movement corrections, especially under conditions of relative motion of the body and target.