Poster F49, Tuesday, March 28, 8:00 – 10:00 am, Pacific Concourse
Exploring Grey and White Matter Correlates of Verbal Working Memory Using Structural Imaging
Maria Ivanova1,2, Olga Dragoy1,3, Svetlana Kuptsova1,4, Akinina Yulia1,5, Petryshevskii Alexey4, Fedinа Oksana4, Dronkers Nina1,2,6; 1National Research University Higher School of Economics, Moscow, Russia, 2Center for Aphasia and Related Disorders, VA Northern California Health Care System, Martinez, California, USA, 3Moscow Research Institute of Psychiatry, Moscow, Russia, 4Center for Speech Pathology and Neurorehabilitation, Moscow, Russia, 5University of Groningen, Groningen, The Netherlands, 6University of California, Davis, California, USA
We investigated the neural substrate of verbal working memory (WM) with a contemporary method of lesion analysis – voxel-based lesion symptom mapping (VLSM) – and analysis of integrity of fiber pathways as revealed by diffusion-tensor imaging. We administered two most common verbal WM tasks – complex listening span and word 2-back – to individuals with left hemisphere stroke (n=41). Lesions were traced manually in native space based on T1 (1 mm isovoxel), T2, FLAIR images, and then registered to the MNI template for VLSM analysis. The fractional anisotropy (FA) metric derived from diffusion-weighted images (bval=1000, dir=20, 2 repetitions, 2.7 mm isovoxel) was used to evaluate integrity of major left hemisphere white matter tracts. Results of the VLSM analyses revealed that critical regions for successful performance on the complex span task were in the inferior and middle frontal gyri, while for the 2-back task they were in the superior and middle temporal gyri. Correlational analyses of mean FA from tracts with WM measures revealed significant relationship between temporal tracts and performance only for the complex listening span task. Thus, the two tasks depend on the structural integrity of different, non-overlapping frontal and temporal grey and white matter brain regions, suggesting distinct neural and cognitive mechanisms triggered by the two tasks. The present study demonstrated that the substrate for verbal WM has been misrepresented in the past due to an over-reliance on functional neuroimaging data, and that the mechanisms of each task have been unjustly ignored in the interpretation of observed findings.
Topic Area: EXECUTIVE PROCESSES: Working memory