title: Electrophysiological correlates of categorization: P300 amplitude as index of target similarity.
abstract: Two experiments examined event-related potentials (ERPs) and behavioral correlates of categorizing stimuli varying in perceptual similarity to targets. Participants performed a target-detection task in which non-target stimuli varied in target similarity but occurred with equivalent probability. The stimuli were variations of a schematic human face comprised of eight distinct features: two eyes, two eyebrows, one nose, one mouth, and two ears. Non-target stimuli that were perceptually similar to targets produced larger P300-like neurophysiological responses than did other non-target stimuli. These effects emerged whether participants' target was relatively complex (eight features) or quite simple (zero features). Accordingly, the presence of many constituent elements of a test stimulus does not appear necessary to trigger increases in categorical processing of non-targets that are similar to a target. The data further suggest that the P300 amplitude may be used as a good index of perceptual similarity between target and non-target stimuli.
authors.affiliation: The Scripps Research Institute, Cognitive Electrophysiology Laboratory, Department of Neuropharmacology, 10550 North Torrey Pines Road, TPC-10, La Jolla, CA 92037, USA. azizian@scripps.edu
authors.forename: A
authors.initials: A
authors.lastname: Azizian
authors.forename: A L
authors.initials: AL
authors.lastname: Freitas
authors.forename: T D
authors.initials: TD
authors.lastname: Watson
authors.forename: N K
authors.initials: NK
authors.lastname: Squires
mesh_terms: D000293:Adolescent; D000328:Adult; D001143:Arousal / Q000502:physiology; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology; D003210:Concept Formation / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology*; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005145:Face; D005260:Female; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology