Online visual control of the arm

The psychophysical and cerebrocortical mechanisms in visually guided reaching movements and isometric force pulses are discussed. The results of psychophysical studies of pointing movements have demonstrated a tight coupling between the visual information and the direction of the movement, and those of studies of directed isometric force pulses have documented the sensitive dependence of the motor system on the continuous availability of visual information for the ongoing correction of directional deviations from the instructed direction. Recordings of the activity of single cells in the motor cortex and parietal areas 2 and 5 have revealed the same tight, online coupling between visual information and cell discharge, and have partially elucidated the neural mechanisms underlying this function at the cortical level.