Posterior parietal association cortex of the monkey: command functions for operations within extrapersonal space

The authors present here the results of a survey of the functional organization of the posterior parietal areas of the monkey cerebral cortex, made in waking monkeys trained to respond with simple behavioral acts on detection of certain sequences of sensory stimuli. Their results lead to a hypothesis of the function of the posterior parietal cortex: these regions receive afferent signals descriptive of the position and movement of the body in space, and contain a command apparatus for operation of the limbs, hands and eyes within immediate extrapersonal space. This general command function is exercised in a holistic fashion. It relates to acts aimed at certain behavioral goals and not to the details of muscular contraction during execution. These details are, on this hypothesis, made precise by the motor system, for which it is well suited by virtue of its powerful mechanisms for specifying movement exactly. The authors believe that their findings provide a positive image of some of the behavioral defects that appear in humans and monkeys after lesions of the posterior parietal areas.