Chapter 8 - Object-Category Processing, Perceptual Awareness, and the Role of Attention during Motion-Induced Blindness

Abstract

Perceptual information represented in the brain, whether a viewer is aware of it or not, holds the potential to influence subsequent behavior. Here we tracked a well-established event-related-potential (ERP) measure of visual-object-category processing, the face-specific ventrolateral-occipital N170 response, across conditions of perceptual awareness. To manipulate perceptual awareness, we employed the motion-induced-blindness (MIB) paradigm, in which covertly attended, static, visual-target stimuli that are superimposed on a globally moving array of distractors perceptually disappear and reappear. Subjects responded with a button press when the target images (faces and houses) actually physically occurred (and thus perceptually appeared) and when they perceptually reappeared after an MIB episode. A comparison of the face-specific N170 ERP activity (face-vs-house responses) revealed robust face-selective ERP activity for physically appearing images and no such activity for perceptual reappearances following MIB episodes, suggesting that face-specific processing had continued uninterrupted during MIB. In addition, electrophysiological activity preceding an actual appearance of a target image, collapsed across face and house image types, was compared to that preceding the perceptual reappearance of a continuously present image (following MIB). This comparison revealed a parietally distributed positive-polarity response that preceded only reappearances following MIB. Such a result suggests a possible role of parietally mediated attentional capture by the present-but-suppressed target in the reestablishment of perceptual awareness at the end of an MIB episode. The present results provide insight into the level of visual processing that can occur in the absence of awareness, as well as into the mechanisms underlying MIB and its influence on perceptual awareness.