title: To bind or not to bind: addressing the question of object representation in visual short-term memory.
abstract: Visual short-term memory (VSTM) is a capacity limited resource, which is consistently estimated to hold about four visual items at a time. There is, however, debate in the literature about what constitutes an "item" and how resources are allocated within VSTM. Some research suggests information is stored in VSTM as discrete objects; however, there is also evidence suggesting that within-object features alter VSTM performance. The present study addresses the question of whether VSTM load effects reflect the number of discrete objects and/or the number of within-object features. An electrophysiological correlate of VSTM--the contralateral delay activity (CDA)--was measured while participants performed a lateralized change-detection task, in which to-be-remembered items varied in the number of features and locations. Each trial contained either a solitary simple feature (shape, color, or orientation) or one of two multifeature arrays: three features presented at three separate locations or three features bound at one location. While presenting multiple features--regardless of whether they are at discrete locations or bound within a single object--resulted in greater CDA amplitude relative to a solitary feature, there was a dissociation in the distribution of activity between the two multifeature conditions, such that the CDA at site P1/P2 was sensitive to the number of discrete objects, while activity at P7/P8 was most enhanced when multiple features were bound in one object. The findings demonstrate the inhomogeneity of the CDA and suggest this electrophysiological marker may reflect both discrete object individuation/separation and flexible feature-feature binding in VSTM.
authors.affiliation: Department of Psychology, University of Toronto, Ontario, Canada. kristin.wilson@utoronto.ca
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Wilson
authors.forename: Maha
authors.initials: M
authors.lastname: Adamo
authors.forename: Morgan D
authors.initials: MD
authors.lastname: Barense
authors.forename: Susanne
authors.initials: S
authors.lastname: Ferber
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D003118:Color Perception / Q000502:physiology*; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D055815:Young Adult