| Natural vision is an active process combining periods of fixation with intermittent gaze shifts or saccadic eye movements. Saccades rapidly direct gaze to visual stimuli while periods of fixation allow the foveal image to be inspected for local singularities and the peripheral image to be analyzed to select the destination of an impending saccade. An experimental tool used by researchers to study this visual behaviour is the visual search paradigm---an adaptable task that reproduces the real-world challenge of selecting a single target from amongst distractors. Studies using this experimental approach have suggested that saccade targets are selected via a process that allows concurrently maintained stimulus representations to compete for limited perceptual resources. This suggestion has been supported by the results of visual search studies in humans, in which eye movements were monitored, and by studies in primates, in which single neurons were recorded within the executive saccadic centres of the brain---the superior colliculus (SC) and the frontal eye fields (FEF). However, because the neural representations of target and distractor stimuli have never been recorded simultaneously, direct evidence supporting the role of parallel and competitive mechanisms in saccade target selection has not been provided. (Abstract shortened by UMI.)... |
