Distributed and Overlapping Neural Substrates for Object Individuation and Identification in Visual Short-Term Memory

Claire K. Naughtin, Jason B. Mattingley, Paul E. Dux

Object individuation and identification are 2 key processes involved in representing visual information in short-term memory (VSTM). Individuation involves the use of spatial and temporal cues to register an object as a distinct perceptual event relative to other stimuli, whereas object identification involves extraction of featural and related conceptual properties of a stimulus. Together, individuation and identification provide the "what," "where," and "when" of visual perception. In the current study, we asked whether individuation and identification processes are underpinned by distinct neural substrates, and to what extent brain regions that reflect these 2 operations are consistent across encoding, maintenance, and retrieval stages of VSTM. We used functional magnetic resonance imaging to identify brain regions that represent the number of objects (individuation) and/or object features (identification) in an array. Using univariate and multivariate analyses, we found substantial overlap between these 2 operations in the brain. Moreover, we show that regions supporting individuation and identification vary across distinct stages of information processing. Our findings challenge influential models of multiple-object encoding in VSTM, which argue that individuation and identification are underpinned by a limited set of nonoverlapping brain regions.