Information used by the perceptual and oculomotor systems regarding the amplitude of saccadic and pursuit eye movements

Abstract

Measures were designed to assess the steady-state information about amplitude of eye movement used for performance of a visual localization task and for control of voluntary saccades. Each measure was applied to four experimental eye movement situations: a saccade in the dark, a saccade to a visible target, a single half-cycle, and the last of 5 half-cycles of pursuit of a target moving in a straight path with sinusoidal velocity at 0.33 Hz. The data indicate that, concerning a just-completed eye movement, (1) information available for control of voluntary saccades is no different from that used to perform a visual localization task, (2) pursuit of a target moving repetitively over a path is subject to considerable underestimation (33%) compared to pursuit of a single sweep of target motion (11% underestimation) and (3) retinal information concerning “intended” saccade amplitude is utilized in judging the amplitude of the saccade which actually occurs. The ERS alone, however, is quite accurate and underestimates saccade amplitude by less than 4%.