title: Partial dissociation in the neural bases of VSTM and imagery in the early visual cortex.
abstract: Visual short-term memory (VSTM) and visual imagery are believed to involve overlapping neuronal representations in the early visual cortex. While a number of studies have provided evidence for this overlap, at the behavioral level VSTM and imagery are dissociable processes; this begs the question of how their neuronal mechanisms differ. Here we used transcranial magnetic stimulation (TMS) to examine whether the neural bases of imagery and VSTM maintenance are dissociable in the early visual cortex (EVC). We intentionally used a similar task for VSTM and imagery in order to equate their assessment. We hypothesized that any differential effect of TMS on VSTM and imagery would indicate that their neuronal bases differ at the level of EVC. In the "alone" condition, participants were asked to engage either in VSTM or imagery, whereas in the "concurrent" condition, each trial required both VSTM maintenance and imagery simultaneously. A dissociation between VSTM and imagery was observed for reaction times: TMS slowed down responses for VSTM but not for imagery. The impact of TMS on sensitivity did not differ between VSTM and imagery, but did depend on whether the tasks were carried concurrently or alone. This study shows that neural processes associated with VSTM and imagery in the early visual cortex can be partially dissociated.
authors.affiliation: Brain Research Unit, O.V. Lounasmaa Laboratory, School of Science, Aalto University, 00076 Espoo, Finland; Institute of Behavioral Sciences, University of Helsinki, 00014 Helsinki, Finland. Electronic address: saad.ely@gmail.com.
authors.forename: Elyana
authors.initials: E
authors.lastname: Saad
authors.affiliation: Department of Biomedical Engineering and Computational Science BECS, Aalto University, 02150 Espoo, Finland.
authors.forename: Maria
authors.initials: M
authors.lastname: Wojciechowska
authors.affiliation: Brain Research Unit, O.V. Lounasmaa Laboratory, School of Science, Aalto University, 00076 Espoo, Finland; Department of Psychology, Faculty of Science and Technology, University of Westminster, 309 Regent Street, London W1B 2HW, UK.
authors.forename: Juha
authors.initials: J
authors.lastname: Silvanto
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007092:Imagination / Q000502:physiology*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Early visual cortex; TMS; VSTM; Visual imagery