Limb segment information transmission capacity infers integrity of spinal transmission tracts and cortical visual-motor control.

Limb segment movement times have been investigated previously in relation to Fitts' Index of Difficulty (ID = log22A/W) over various movement distances (Leisman, 1987; 1989a). Results supported Fitts' theory that different limb segments show different maximum information processing rates. The results indicated that visually-mediated discrete correction control processes are used. In the presently reported experiments, normal human subjects performed movements with left or right arms. Visual-motor control was inter- or intrahemispheric. Direction of movement was adductive or abductive. It was hypothesized that abductive movements are controlled by the contralateral hemisphere while adductive movements are controlled by either hemisphere. It was also hypothesized that abductive movements are related to the lateral system which projects to the contralateral side of the spinal cord. The control of adductive movements is related to the medial system which projects bilaterally to the spinal cord.