title: Bilateral generic working memory circuit requires left-lateralized addition for verbal processing.
abstract: According to the Baddeley-Hitch model, phonological and visuospatial representations are separable components of working memory (WM) linked by a central executive. The traditional view that the separation reflects the relative contribution of the 2 hemispheres (verbal WM--left; spatial WM--right) has been challenged by the position that a common bilateral frontoparietal network subserves both domains. Here, we test the hypothesis that there is a generic WM circuit that recruits additional specialized regions for verbal and spatial processing. We designed a functional magnetic resonance imaging paradigm to elicit activation in the WM circuit for verbal and spatial information using identical stimuli and applied this in 33 healthy controls. We detected left-lateralized quantitative differences in the left frontal and temporal lobe for verbal > spatial WM but no areas of activation for spatial > verbal WM. We speculate that spatial WM is analogous to a "generic" bilateral frontoparietal WM circuit we inherited from our great ape ancestors that evolved, by recruitment of additional left-lateralized frontal and temporal regions, to accommodate language.
authors.affiliation: Oxfordshire and Buckinghamshire Partnership National Health Service Trust, Warneford Hospital, Warneford Lane, Oxford OX3 7JX, UK. manaan.ray@psych.ox.ac.uk
authors.forename: Manaan Kar
authors.initials: MK
authors.lastname: Ray
authors.forename: Clare E
authors.initials: CE
authors.lastname: Mackay
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Harmer
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Crow
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D014705:Verbal Behavior / Q000502:physiology*