title: A hemodynamic correlate of lateralized visual short-term memories.
abstract: Neuroimaging studies attempting to isolate the neural substrate of visual short-term memory in humans have concentrated on the behavior of neurons populating the posterior part of the parietal cortex as a possible source of visual short-term memory capacity limits. Using a standard change-detection task, fMRI studies have shown that maintenance of bilaterally encoded objects elicited bilateral increases of hemodynamic activation in the intra-parietal and intra-occipital sulci (IPS-IOS) proportional to the number of objects retained in visual short-term memory. We used a spatially cued variant of the change-detection task to record hemodynamic responses to unilaterally encoded objects using functional near-infrared spectroscopy (fNIRS). Electrophysiological studies that employed this task have shown that maintenance of unilaterally encoded objects elicited posterior unilateral (contralateral) increase in event-related negativity proportional to the number of objects retained in visual short-term memory. We therefore examined whether contralateral increases in oxy-hemoglobin concentration correlated with the number of retained objects. Contrary to the idea that bilateral increases in BOLD responses and unilateral increases in event-related negativity may be different reflections of the same underlying neural/functional processing, memory-related increases in oxy-hemoglobin concentration were found bilaterally even when objects had to be encoded unilaterally. The present findings suggest that EEG and fMRI/fNIRS techniques reveal distinct neural signatures of the mechanisms supporting visual short-term memory.
authors.affiliation: Department of Developmental Psychology, University of Padova, Padova, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Cutini
authors.forename: Fabio
authors.initials: F
authors.lastname: Scarpa
authors.forename: Pietro
authors.initials: P
authors.lastname: Scatturin
authors.forename: Pierre
authors.initials: P
authors.lastname: Jolicœur
authors.forename: Patrik
authors.initials: P
authors.lastname: Pluchino
authors.forename: Marco
authors.initials: M
authors.lastname: Zorzi
authors.forename: Roberto
authors.initials: R
authors.lastname: Dell'Acqua
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000098:blood supply / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003265:Contingent Negative Variation; D004192:Discrimination, Psychological / Q000502:physiology; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009778:Occipital Lobe / Q000098:blood supply / Q000502:physiology; D010296:Parietal Lobe / Q000098:blood supply / Q000502:physiology; D012016:Reference Values; D019265:Spectroscopy, Near-Infrared; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult