A model of saccade generation based on parallel processing and competitive inhibition

Abstract

During active vision, the eyes continually scan the visual environment using saccadic scanning movements. This target article presents an information processing model for the control of these movements, with some close parallels to established physiological processes in the oculomotor system. Two separate pathways are concerned with the spatial and the temporal programming of the movement. In the temporal pathway there is spatially distributed coding and the saccade target is selected from a “salience map.” Both pathways descend through a hierarchy of levels, the lower ones operating automatically. Visual onsets have automatic access to the eye control system via the lower levels. Various centres in each pathway are interconnected via reciprocal inhibition. The model accounts for a number of well-established phenomena in target-elicited saccades: the gap effect, express saccades, the remote distractor effect, and the global effect. High-level control of the pathways in tasks such as visual search and reading is discussed; it operates through spatial selection and search selection, which generally combine in an automated way. The model is examined in relation to data from patients with unilateral neglect.

Crossmodal coupling of oculomotor control and spatial attention in vision and audition

“…While microsaccade rate, an indicator of when saccades occur, seems to be controlled supramodally, microsaccade direction as a measure of where saccades go clearly depends on the modality within which attention is shifted. Intuitively, where a saccade is oriented is determined later than the decision whether to make a saccade at all, a point of view that is also held by models of oculomotor control (e.g., Findlay and Walker 1999). Seemingly, the knowledge that shifts of visual attention or gaze are not required (as in AA) interferes with saccade programming at that later stage resulting in a weaker control of fixation stability in the purely auditory task.…”

“…We already concluded that overall microsaccade rate and microsaccade direction mirror different levels of interaction between attentional and oculomotor processes. Physiological studies (e.g., Carpenter 2000;Wurtz 1996) and theoretical models (e.g., Engbert et al 2002;Findlay and Walker 1999) suggest that the decision when a saccade program is initiated is earlier than where it will be oriented. We argued that the later stage may not be reached in situations which do not require visual attention.…”

“…Of course, models of oculomotor control (e.g. Findlay and Walker 1999;Rizzolatti et al 1987Rizzolatti et al , 1994) have proposed such a coupling of spatial shifts of attention (independent of modality) and the preparation of saccadic movements for some time. The SC is the usual suspect in being a neurological counterpart to these models since it is involved in the coordination of covert shifts of attention (Albano et al 1982;Desimone et al 1989;Kustov and Robinson 1996) and the initiation of saccades (reviews in Munoz et al 2000;Scudder et al 2002;Sparks 2002).…”

Development of a Cued Pro- and Antisaccade Paradigm: An Indirect Measure to Explore Automatic Components of Sexual Interest

“…Changes in the peripheral field of vision support exogenous triggering resulting in automatic saccades, while internal states support endogenous triggering resulting in intentional saccades (Liversedge, Gilchrist, & Everling, 2011). Findlay and Walker (1999) suggested that the simultaneous occurrence of exogenous and endogenous mechanisms might result in conflicts if working in opposite directions. Findings from Massen (2004) support the assumption of a parallel automatic and intentional generation of saccades, whereby only saccades with competitive advantages are performed.…”

“…Saccadic eye movements can be performed both in an automatic and a controlled manner (Findlay & Walker, 1999). Specifically, we wanted to explore saccades towards (prosaccades) or away from (antisaccades) sexually relevant or irrelevant targets as indicators of early attentional sexual information processing.…”