No evidence for an independent retinotopic reference frame for inhibition of return.

Inhibition of return (IOR) represents a delay in responding to a previously inspected location and is viewed as a crucial mechanism that sways attention toward novelty in visual search. Although most visual processing occurs in retinotopic, eye-centered, coordinates, IOR must be coded in spatiotopic, environmental, coordinates to successfully serve its role as a foraging facilitator. Early studies supported this suggestion but recent results have shown that both spatiotopic and retinotopic reference frames of IOR may co-exist. The present study tested possible sources for IOR at the retinotopic location including being part of the spatiotopic IOR gradient, part of hemifield inhibition and being an independent source of IOR. We conducted four experiments that alternated the cue-target spatial distance (discrete and contiguous) and the response modality (manual and saccadic). In all experiments, we tested spatiotopic, retinotopic and neutral (neither spatiotopic nor retinotopic) locations. We did find IOR at both the retinotopic and spatiotopic locations but no evidence for an independent source of retinotopic IOR for either of the response modalities. In fact, we observed the spread of IOR across entire validly cued hemifield including at neutral locations. We conclude that these results indicate a strategy to inhibit the whole cued hemifield or suggest a large horizontal gradient around the spatiotopically cued location. PUBLIC SIGNIFICANCE STATEMENT: We perceive the visual world around us as stable despite constant shifts of the retinal image due to saccadic eye movements. In this study, we explore whether Inhibition of return (IOR), a mechanism preventing us from returning to previously attended locations, operates in spatiotopic, world-centered or in retinal, eye-centered coordinates. We tested both saccadic and manual IOR at spatiotopic, retinotopic, and control locations. We did not find an independent retinotopic source of IOR for either of the response modalities. The results suggest that IOR spreads over the whole previously attended visual hemifield or there is a large horizontal spatiotopic gradient. The current results are in line with the idea of IOR being a foraging facilitator in visual search and contribute to our understanding of spatiotopically organized aspects of visual and attentional systems.