Abstract
Inhibition of return (IOR), a performance decrement for stimuli appearing at recently cued locations, occurs when the target and cue share the same screen-position (i.e. spatiotopic mapping; Posner and Cohen, 1984; Maylor and Hockey, 1985). This is in contrast to cue-based attention-facilitation effects that were recently suggested to be mapped in a retinotopic reference frame (Golomb et al., 2008), the prevailing representation throughout early visual processing stages. Here, we investigate the dynamics of IOR formation in both reference frames, using a modified cued-location reaction-time task with an intervening saccade between cue and target presentation. This enabled creating trials in which the target was present at the same retinotopic location as the cue, and trials with the same screen-position (spatiotopic trials). IOR was primarily found for targets appearing at the same spatiotopic position as the initial cue, when the cue and target were presented at the same visual hemifield, as early as 10 ms after the intervening saccade ended. Therefore, under these experimental conditions, the representation of previously attended locations is not remapped after the execution of a saccade. Rather, either a retinotopic representation is remapped prior to the end of the saccade (using prospective motor command) or the position of the cue and target are encoded in spatiotopic reference frame, regardless of eye position. We suggest that deficits in the formation of such spatiotopic representation due to right parietal lesions may explain classical aspects of neglect syndrome, such as re-fixating previously visited targets on a visual search task.
This work was supported by the National Institute for Psychobiology in Israel (NIPI) grant 2-2008-09 to GA and an Israel Science Foundation (ISF) grant to EZ.