PARIETAL CORTEX AREA-5 AND VISUOMOTOR BEHAVIOR

For years, area 5 of the parietal cortex was thought to be a somatic s ensory structure. This view was challenged by recordings during active movements in alert behaving monkeys, which suggested that area 5 also contained populations of neurons that issued nonspecific, context-dep endent ''commands'' about intended motor responses. Recent studies hav e revealed that area 5 generates a representation of the spatiotempora l form of arm movements and arm postures, although the parameter space of that representation is still controversial. They also showed that many area 5 cells are recipient to centrally generated signals about t he motor relevance of external sensory signals. These new results supp ort the hypothesis that area 5 contributes to the sensorimotor guidanc e of motor behavior, by contributing to the somatomotor and visuomotor transformations presumed to underlie visually guided behavior. Howeve r, area 5 appears to be less directly implicated than the premotor cor tex in the process of selecting the nature of the response to instruct ional signals.