Visual Perception and Eye Movements

Abstract

Our perception of the world appears to be steady and focused, despite the fact that our eyes are constantly moving. In this chapter, we review studies on the neural mechanisms and visual phenomena that endow us with stable visual perception despite frequent eye movements and gaze shifts. We describe how sensitivity to stationary and moving stimuli is suppressed just before and during a saccadic eye movement, a phenomenon referred to as saccadic suppression. We also depict the neural correlates of saccadic suppression based on studies conducted in alert monkeys during single-unit recordings and in human subjects using functional MRI. In addition to saccadic suppression, the phenomena of saccadic suppression of displacement and saccadic mislocalization suggest that motion sensitivity and perceived location of objects are altered during eye movements. For example, target motion during saccades goes largely unnoticed. Clearly visible targets that are flashed during an eye movement are apparently displaced towards the location of the end point of the saccade. These findings suggest that visual perception is based on the spatio-temporal integration of information gathered during sequential fixation periods. To ensure stability of our percepts during eye movements, some form of compensation or remapping must take place to compensate for retinal displacements of stimuli in a viewed scene. We also examine the interactions that take place between motion perception and pursuit eye movement. Furthermore, we review findings from behavioral, psychophysical and imaging studies in human observers and single-unit recordings in non-human primates that are relevant to perceptual phenomena arising during saccadic and pursuit eye movements. These studies suggest that conscious vision results from the dynamic interplay between sensory and motor processes. Specifically, we propose that our perception of the visual world is built up over time during consecutive fixations.