Motor actions are imprecise to some degree. I will use smooth pursuit eye movements to evaluate the source of trial-by-trial variations in smooth pursuit eye movement. First, I will show that the variation in the behavior is small compared to the imprecision of the representation of target motion in extrastriate visual area MT. The variation in pursuit can be accounted for in sensory coordinates, in terms of errors in estimating the direction, speed, and timing of target motion. Further, the precision of pursuit is comparable to the precision of perceptual reports of the direction and speed of target motion, suggesting a common, sensory source of variation in perception and action. Second, I will show that there are remarkably strong trial-by-trial correlations between the simple spike firing of floccular Purkinje cells and the eye velocity of pursuit. I will argue that there has been substantial noise reduction between area MT and the cerebellum, consistent with the hypothesis that the main source of variation in pursuit comes from errors in estimating the sensory parameters of target motion.

• Presentation: Lisberber-Sloan-Swartz-summer-2005.ppt (2.3Mb)