Disparity vergence eye movements occasionally exhibit two high-velocity components to a single step stimulus (Alvarez, T. L., Semmlow, J. L. and Yuan, W. (1998). Journal of Neurophysiology, 79, 37-44). This research investigates the neural strategy used to trigger the second component of double high-velocity vergence eye movements. Vergence doubles evoked by an experimental protocol that induces post-movement visual error were compared to doubles that occur normally. The second component of a visually evoked response double occurred later, and with slower dynamics, than that of a naturally occurring double. These differences in timing and dynamics indicate that natural double responses are mediated, at least in part, by a mechanism other than visual feedback. The faster dynamics and timing of natural doubles suggest that an internal monitoring process triggers these movements.
Alvarez, T. L., Semmlow, J. L., Yuan, W., & Munoz, P. (2000). Disparity vergence double responses processed by internal error. Vision Research, 40(3), 341–347. https://doi.org/10.1016/S0042-6989(99)00175-3