Abstract
In the lab, smooth pursuit and the vestibulo-ocular reflex (VOR) are often studied in isolation, whereas in nature, they work simultaneously. To see how these systems operate in conjunction, we sought to decompose the eye velocity signal during head-free gaze pursuit two components: one attributable to stimulus motion and another due to head movement. To accomplish this, human subjects tracked a target dot moving at constant velocity plus a noisy perturbation term across large excursions (67 deg). Subjects were free to move their heads and both head and eye movements were recorded. Using regression, we recovered linear filters describing the relative contributions of stimulus movement and head movement to the eye movement. We could account for over 50% of the variance of the eye movements from these two components. The stimulus component was similar to previously reported filters derived from head-fixed smooth pursuit maintenance(Tavassoli and Ringach, 2009). The head movement component is consistent with a partially unsuppressed VOR. We found no evidence for any further coordination mechanism or shared noise source as the cross-covariance between head and eye velocities could be explained by the partially unsuppressed VOR. In conclusion, we were able to separate linear components of the smooth pursuit and VOR without external perturbations of the head during gaze pursuit maintenance which could account for a significant portion of eye movement variability. Tavassoli, A. and D. L. Ringach (2009). "Dynamics of smooth pursuit maintenance." J Neurophysiol 102(1): 110-118.
Meeting abstract presented at VSS 2012