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Poster B10, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

Role of Left Hemisphere Language Areas in Visuospatial Working Memory

Juliana Baldo1, Selvi Paulraj1,2, Krista Parker1, Brian Curran1, Nina Dronkers1,3;1VA Northern California Health Care System, 2Palo Alto University, 3University of California, Davis

Visuospatial functioning involves the ability to conceptualize and use visual and spatial representations to execute a task. A disruption in this system can affect processes as diverse as attention, memory, drawing, locomotion, and navigation. Traditionally, visuospatial functioning has been associated with posterior regions of the brain, usually parietal cortex, particularly in the right hemisphere (RH). While there is ample evidence that the RH plays a special role in visuospatial functioning, deficits have also been observed in patients with left hemisphere (LH) lesions on tests ranging from visual memory to drawing to spatial attention. The source of such deficits has been unclear, with some studies suggesting a direct impact of language functioning on visuospatial performance. Other studies have suggested that visuospatial impairment in LH patients arises from damage to homologous regions in the LH that also support visuospatial processing. Thus far, small sample sizes have made it difficult to draw strong conclusions. In the current study, 71 individuals with a history of a single, chronic left hemisphere stroke and a range of aphasia severity were administered the Spatial Span subtest of the WMS-III, which includes forward and backward spatial span. The behavioral and lesion data were analyzed using voxel-based lesion symptom mapping (VLSM) software that allowed us to identify brain regions in the left hemisphere most critical for forward and backward spatial span. Results: Backward spatial span showed significant differences between aphasia types, with lower scores in participants with more severe aphasia, particularly Broca’s aphasia. However, there were no significant differences on forward spatial span. Voxel-based lesion symptom mapping (VLSM) was then applied to identify critical left hemisphere correlates of spatial span performance. The voxels associated with spatial span (both forward and backward) were located in left posterior superior temporal and inferior parietal cortex, regions associated with phonological storage components of verbal working memory. The current findings suggest that language and associated areas in the posterior left hemisphere play a role in visuospatial working memory. These results are consistent with prior findings showing that subtle changes in visuospatial processing (e.g., spatial attention) occur following left hemisphere stroke, and suggest that visuospatial functioning is supported in part by the left hemisphere.

Topic Area: Control, Selection, and Executive Processes

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