The evidence for pre-programming in the control of disparity vergence

Recent evidence has shown that there are two neural control processes involved in disparity vergence motor control: a fast component and a slow component. The fast component provides the major drive for the initial portion of the transient response (the first 300 ms of the movement) and appears to be open-loop. In the present work, the authors investigate the relationship between the fast component and the stimulus features which selectively activate this component. It is shown that neither presentation time (as brief as 50 ms) nor target size affects the amplitude of the initial component; however, the stimulus amplitude does influence the initial component amplitude. These results indicate that the initial component of the dynamic vergence response is mediated by preprogrammed control.