Eye-hand coordination and visual control of reaching: studies in behaving animals

The function of eye-hand coordination and visual control of movement has been studied in both human subjects and experimental animals. Psychophysical experiments in healthy subjects and observations in brain-damaged patients (Jeannerod, 1986) have provided important information concerning these functions and the possible role of neural structures involved in its control. On the other hand, studies in experimental animals have provided valuable insights into the neural mechanisms that may underlie the specification and control of parameters of visuomotor coordination.A powerful technique for studying the neurophysiological basis of behavior is the recording of the activity of brain cells in animals performing particular tasks (Lemon, 1984). First, animals are trained to perform in certain tasks using reward-based operant conditioning techniques. Then, the activity of single cells in selected brain areas is recorded during task performance using microelectrodes inserted into the brain through the dura. This is the most direct technique and one with a fine grain for studying the neural mechanisms of behavior. The first stage in these studies is the training of naive animals to perform appropriate behavioral tasks. This training serves three goals: First, it prepares the animal for the subsequent recording sessions; second it, provides an insight into how the behavior is being shaped from the naive condition to the "learned" condition; and third, it permits a comparison between the behavioral capacities of animals and human subjects, so that findings from animals can be extended to human subjects. I illustrate these interwoven aspects with a series of studies that were aimed at elucidating some of the cerebrocortical mechanisms involved in arm movements directed to visual targets in immediate extrapersonal space.