title: Frontal and parietal theta burst TMS impairs working memory for visual-spatial conjunctions.
abstract: In tasks that selectively probe visual or spatial working memory (WM) frontal and posterior cortical areas show a segregation, with dorsal areas preferentially involved in spatial (e.g. location) WM and ventral areas in visual (e.g. object identity) WM. In a previous fMRI study [1], we showed that right parietal cortex (PC) was more active during WM for orientation, whereas left inferior frontal gyrus (IFG) was more active during colour WM. During WM for colour-orientation conjunctions, activity in these areas was intermediate to the level of activity for the single task preferred and non-preferred information. To examine whether these specialised areas play a critical role in coordinating visual and spatial WM to perform a conjunction task, we used theta burst transcranial magnetic stimulation (TMS) to induce a functional deficit. Compared to sham stimulation, TMS to right PC or left IFG selectively impaired WM for conjunctions but not single features. This is consistent with findings from visual search paradigms, in which frontal and parietal TMS selectively affects search for conjunctions compared to single features, and with combined TMS and functional imaging work suggesting that parietal and frontal regions are functionally coupled in tasks requiring integration of visual and spatial information. Our results thus elucidate mechanisms by which the brain coordinates spatially segregated processing streams and have implications beyond the field of working memory.
authors.affiliation: Wolfson Centre for Clinical and Cognitive Neuroscience and Wales Institute of Cognitive Neuroscience, School of Psychology, Bangor University, Penrallt Road, Gwynedd, LL57 2AS, UK. h.morgan@bangor.ac.uk
authors.forename: Helen M
authors.initials: HM
authors.lastname: Morgan
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Jackson
authors.forename: Martijn G
authors.initials: MG
authors.lastname: van Koningsbruggen
authors.forename: Kimron L
authors.initials: KL
authors.lastname: Shapiro
authors.forename: David E J
authors.initials: DE
authors.lastname: Linden
mesh_terms: D000328:Adult; D001931:Brain Mapping; D003118:Color Perception / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009949:Orientation / Q000502:physiology; D010296:Parietal Lobe / Q000502:physiology*; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*