Dissociation of visual, motor and predictive signals in parietal cortex during visual guidance

The role of the posterior parietal cortex (PPC) in the visual guidance of m ovements was studied in monkeys trained to use a joystick to guide a spot t o a target. Visual and motor influences were dissociated by transiently occ luding the spot and by varying the relationship between the direction of jo ystick and spot movements. We found a strong segregation of function in PPC during visual guidance. Neurons in area MST were selectively modulated by the direction of visible moving stimuli, whereas neurons in area MIP were s electively modulated by the direction of hand movement. In contrast, the se lectivity of cells in the lateral intraparietal area (LIP) did not directly depend on either visual input or motor output, but rather seemed to encode a predictive representation of stimulus movement. These predictive signals may be an important link in visuomotor transformations.