Visuomotor transformations: early cortical mechanisms of reaching

Recent studies of visually guided reaching in monkeys support the hypothesi s that the visuomotor transformations underlying arm movements to spatial t argets involve a parallel mechanism that simultaneously engages functionall y related frontal and parietal areas linked by reciprocal cortico-cortical connections. The neurons in these areas possess similar combinations of res ponse properties. The multimodal combinatorial properties of these neurons and the gradient architecture of the parieto-frontal network emerge as a po tential substrate to link the different sensory and motor signals that aris e during reaching behavior into common hybrid reference frames. This conver gent combinatorial process is evident at early stages of visual information processing in the occipito-parietal cortex, suggesting the existence of re -entrant motor influences on cortical areas once believed to have only visu al functions.