Abstract
After presenting a peripheral cue, a subsequent saccade to the cued location is delayed (inhibition-of-return; IOR). Furthermore, saccades typically deviate away from the cued location. The present study examined the relationship between these inhibitory effects. Even though the results suggested a relationship between oculomotor IOR and saccade trajectory deviations, a dissociation was found in their time course. Saccade trajectory deviations were rapidly reduced as the time between cue and the saccade increased. In contrast, IOR was found at longer delays between cue and saccade. Additional experiments show that objects presented at previously inhibited location do not compete for selection anymore. We propose that oculomotor IOR is caused by inhibition in the attentional system and saccade trajectory deviations are caused by inhibition in the oculomotor system.
The findings are in line with a recently suggested competitive integration model of saccade programming (1) which assumes that endogenous and exogenous saccades are programmed in a common saccade map. The model incorporates a lateral interaction structure in which saccade-related activation at a specific location spreads to neighboring locations, but inhibits distant locations. In addition, there is top-down location specific inhibition of locations to which the saccade should not go. This inhibition results in saccades that deviate away from the inhibited location. The superior colliculus seems to incorporate all the functionality necessary for a saccade map. The FEF and the dorso-lateral prefrontal cortex (dlPFC) are prime candidates for attentional location specific top-down inhibition that is applied to the SC.
(1)
GodijnR.TheeuwesJ.(2002). Programming of exogenous and endogenous saccades: Evidence for a competitive integration model. Journal of Experimental Psychology. Human Perception and Performance 28 (5): 1039–1054