Poster C80, Wednesday, August 21, 2019, 10:45 am – 12:30 pm, Restaurant Hall
Neural correlates of verbal working memory revealed through voxel-based morphometry
Maryam Ghaleh1, Elizabeth Lacey1,2, Mackenzie Fama1,3, Zainab Anbari1, Candace van der Stelt1, Stephen Tranchina1, Peter Turkeltaub1,2;1Georgetown University Medical Center, 2MedStar National Rehabilitation Hospital, 3Towson University
INTRODUCTION: The neural basis of verbal working memory (WM) is still a matter of debate. Studies have suggested two separate mechanisms for maintenance of verbal information in WM (Leff et al., 2009, Trost & Gruber, 2012). In our recent multivariate lesion-symptom-mapping study of left-hemisphere stroke survivors, we found sensorimotor cortex to be crucial to the articulatory-rehearsal process (backward digit span task), and posterior superior temporal gyrus (pSTG) to be crucial to non-articulatory maintenance (forward digit span task). Although several studies have suggested a role for left inferior frontal gyrus (IFG) and Dorsolateral prefrontal cortex (DLPFC), in verbal WM (Gruber & Goshke, 2004), we did not find evidence for the involvement of these regions. It is suggested that bilateral prefrontal areas are involved in WM such that unilateral prefrontal lesions do not cause WM deficits (D'Esposito et al., 2006). The aim of the current study was to investigate neural correlates of WM using voxel-based morphometry (VBM). We examined the roles of right hemisphere and bilateral prefrontal areas, in particular. METHODS: Seventy-one left hemisphere stroke survivors and 39 healthy adults completed four tasks: forward and backward digit span, and forward and backward spatial span. VBM was first used to identify regions in which gray matter volume (GMV) correlated with performance on each task in healthy adults. Additional analyses identified regions in which the correlation between GMV and performance in each task was different between healthy adults and stroke survivors, covarying for age, total GMV, and lesion volume. Threshold-free cluster enhancement was used and family-wise error correction was applied to correct for multiple comparison across the entire brain, along with small volume correction in particular regions of interests, including bilateral IFG, DLPFC, and our previous lesion-symptom mapping results (bilateral sensorimotor areas and pSTG). Reported results are thresholded at p<0.05 corrected. RESULTS: In our first set of analyses, positive correlations were found between GMV in: a) right IFG and forward and backward digit span scores, b) left IFG and right pSTG, and forward digit span scores, and c) left DLPFC and backward digit span scores. No clusters survived correction for spatial span tasks –even at lower thresholds no prefrontal results were found (p<0.5 uncorrected). Our second set of analysis revealed stronger correlations between right IFG and forward and backward digit span tasks in healthy participants compared to patients. We found stronger correlations between bilateral cerebellum and backward digit span in patients compared to healthy adults. CONCLUSION: Our results suggest that right IFG is involved in performing both digit span tasks. Since GMV in IFG did not correlate with spatial spans, it is possible that IFG’s role is domain-specific, perhaps involving integration of episodic information. Our findings also demonstrate that right pSTG is involved in forward digit span and might have a role in non-articulatory maintenance. Left DLPFC might be involved in manipulation of verbal information in WM required for backward digit span task. Bilateral cerebellum is involved in inner speech and might play a role in recovery of articulatory-rehearsal functions after left hemisphere lesions.
Themes: Phonology and Phonological Working Memory, Disorders: Acquired
Method: Other