title: ERP signs of categorical and supra-categorical processing of visual information.
abstract: BACKGROUND
  The aim of the present study was to investigate to what extent shared and distinct brain mechanisms are possibly subserving the processing of visual supra-categorical and categorical knowledge as observed with event-related potentials of the brain. Access time to these knowledge types was also investigated. Picture pairs of animals, objects, and mixed types were presented. Participants were asked to decide whether each pair contained pictures belonging to the same category (either animals or man-made objects) or to different categories by pressing one of two buttons. Response accuracy and reaction times (RTs) were also recorded.
  
  
  RESULTS
  Both ERPs and RTs were grand-averaged separately for the same-different supra-categories and the animal-object categories. Behavioral performance was faster for more endomorphic pairs, i.e., animals vs. objects and same vs. different category pairs. For ERPs, a modulation of the earliest C1 and subsequent P1 responses to the same vs. different supra-category pairs, but not to the animal vs. object category pairs, was found. This finding supports the view that early afferent processing in the striate cortex can be boosted as a by-product of attention allocated to the processing of shapes and basic features that are mismatched, but not to their semantic quintessence, during same-different supra-categorical judgment. Most importantly, the fact that this processing accrual occurred independent of a traditional experimental condition requiring selective attention to a stimulus source out of the various sources addressed makes it conceivable that this processing accrual may arise from the attentional demand deriving from the alternate focusing of visual attention within and across stimulus categorical pairs' basic structural features. Additional posterior ERP reflections of the brain more prominently processing animal category and same-category pairs were observed at the N1 and N2 levels, respectively, as well as at a late positive complex level, overall most likely related to different stages of analysis of the greater endomorphy of these shape groups. Conversely, an enhanced fronto-central and fronto-lateral N2 as well as a centro-parietal N400 to man-made objects and different-category pairs were found, possibly indexing processing of these entities' lower endomorphy and isomorphy at the basic features and semantic levels, respectively.
  
  
  CONCLUSIONS
  Overall, the present ERP results revealed shared and distinct mechanisms of access to supra-categorical and categorical knowledge in the same way in which shared and distinct neural representations underlie the processing of diverse semantic categories. Additionally, they outlined the serial nature of categorical and supra-categorical representations, indicating the sequential steps of access to these separate knowledge types.
authors.affiliation: Cognitive Electrofunctional Imaging Lab, Institute of Molecular Bioimaging and Physiology, National Research Council, Milan, Italy. Electronic address: alberto.zani@ibfm.cnr.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Zani
authors.affiliation: Milan Center for Neuroscience, University of Milan-Bicocca, Milan, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Marsili
authors.affiliation: Milan Center for Neuroscience, University of Milan-Bicocca, Milan, Italy.
authors.forename: Annapaola
authors.initials: A
authors.lastname: Senerchia
authors.affiliation: Cognitive Electrofunctional Imaging Lab, Institute of Molecular Bioimaging and Physiology, National Research Council, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Orlandi
authors.affiliation: Cluster of Excellence "Languages of Emotion", Freie Universität, Berlin, Germany.
authors.forename: Francesca M M
authors.initials: FM
authors.lastname: Citron
authors.affiliation: Cognitive Electrofunctional Imaging Lab, Institute of Molecular Bioimaging and Physiology, National Research Council, Milan, Italy.
authors.forename: Ezia
authors.initials: E
authors.lastname: Rizzi
authors.affiliation: Milan Center for Neuroscience, University of Milan-Bicocca, Milan, Italy.
authors.forename: Alice M
authors.initials: AM
authors.lastname: Proverbio
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D004569:Electroencephalography / Q000379:methods; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D007600:Judgment / Q000502:physiology; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Animals; C1; ERPs; Early modulation; Man-made objects; N400; P1; Selective attention.; Semantic categories; Supra-categorical knowledge