Inhibition of Return without Preparatory Suppression in Spatial Priority Maps

Abstract

Visual attention is thought to operate via spatial priority maps that enhance attended locations and suppress distractors. While sustained enhancement is well established, whether priority maps can maintain sustained suppression at ignored locations remains unclear. Inhibition of return (IOR), slower responses to previously cued locations, provides a critical test case, as the inhibited state persists during the anticipatory interval before target onset. However, whether IOR reflects priority map suppression or arises from motor-/response-level mechanisms remains debated. We addressed this by combining a spatial cueing paradigm with inverted encoding models applied to EEG data ( N  = 24; 12 females, 12 males) to reconstruct spatially selective channel-tuning functions during the anticipatory interval when IOR is behaviorally expressed. Behaviorally, we confirmed robust IOR following nonpredictive peripheral cues, with slower saccadic responses to previously cued locations. Predictive cues produced faster responses and sustained positive tuning at attended locations throughout the anticipatory interval. Reflexive cues, however, showed initial orienting followed by progressive attenuation of spatial tuning, resulting in significantly weaker anticipatory priority than in the predictive condition during the IOR interval. Critically, individual frequency bands did not reveal below-baseline suppression at cued locations during IOR. Furthermore, although placeholders modulated behavioral IOR magnitude and spatial extent, they did not influence anticipatory spatial tuning. These findings indicate that behavioral IOR arises independently of sustained suppression in cortical spatial priority maps, suggesting inhibition operates via motor-/response-level mechanisms or coding schemes not captured by population-level spatial tuning. Our results challenge that behavioral suppression reflects anticipatory reconfiguration of spatial priority.