title: Less Is More: Semantic Information Survives Interocular Suppression When Attention Is Diverted.
abstract: The extent of unconscious semantic processing has been debated. It is well established that semantic information is registered in the absence of awareness induced by inattention. However, it has been debated whether semantic information of invisible stimuli is processed during interocular suppression, a procedure that renders one eye's view invisible by presenting a dissimilar stimulus to the other eye. Inspired by recent evidence demonstrating that reduced attention attenuates interocular suppression, we tested a counterintuitive hypothesis that attention withdrawn from the suppressed target location facilitates semantic processing in the absence of awareness induced by interocular suppression. We obtained an electrophysiological marker of semantic processing (N400 component) while human participants' spatial attention was being manipulated with a cueing paradigm during interocular suppression. We found that N400 modulation was absent when participants' attention was directed to the target location, but present when diverted elsewhere. In addition, the correlation analysis across participants indicated that the N400 amplitude was reduced with more attention being directed to the target location. Together, these results indicate that inattention attenuates interocular suppression and thereby makes semantic processing available unconsciously, reconciling conflicting evidence in the literature. We discuss a tight link among interocular suppression, attention, and conscious awareness.
  
  
  
  Interocular suppression offers a powerful means of studying the extent of unconscious processing by rendering a salient stimulus presented to one eye invisible. Here, we provide evidence that attention is a determining factor for unconscious semantic processing. An electrophysiological marker for semantic processing (N400 component) was present when attention was diverted away from the suppressed stimulus but absent when attention was directed to that stimulus, indicating that inattention facilitates unconscious semantic processing during the interocular suppression. Although contrary to the common sense assumption that attention facilitates information processing, this result is in accordance with recent studies showing that attention modulates interocular suppression but is not necessary for semantic processing. Our finding reconciles the conflicting evidence and advances theories of consciousness.
authors.affiliation: Graduate Program in Cognitive Science and.
authors.forename: Kangyong
authors.initials: K
authors.lastname: Eo
authors.affiliation: Graduate Program in Cognitive Science and.
authors.forename: Oakyoon
authors.initials: O
authors.lastname: Cha
authors.affiliation: Graduate Program in Cognitive Science and Department of Psychology, Yonsei University, Seoul 03722, Republic of Korea.
authors.forename: Sang Chul
authors.initials: SC
authors.lastname: Chong
authors.affiliation: Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon 16419, Republic of Korea, and Department of Psychology, Sungkyunkwan University, Seoul 03063, Republic of Korea kangminsuk@skku.edu.
authors.forename: Min-Suk
authors.initials: MS
authors.lastname: Kang
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D003463:Cues; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D012660:Semantics; D014796:Visual Perception / Q000502:physiology*
keywords: attention; consciousness; event-related potential; interocular suppression