Dissociation of Verbal and Spatial Working Memory in the Fronto-Parietal Network (P07.186)

Abstract

Objective: To examine hemispheric differences between verbal and spatial working memory in a fronto-parietal network using electrophysiologic (ERP) and transcranial magnetic stimulation (TMS) methods. Background Activity in the frontal and parietal cortex vary between working memory (WM) processing stage, load, and stimulus type. However, hemispheric specialization in the WM network is debated. This study aimed to observe hemispheric differences in both verbal and spatial working memory following a unilateral transient lesion. It was hypothesized that ERP would show temporally-specific hemispheric differences in both verbal and spatial WM tasks that could be disrupted with TMS to the prefrontal cortex. Design/Methods: Right-handed adults (n=32, 18 female, mean age 26.2) completed both a verbal and spatial variant of the 2-back task during electrophysiologic recording. Repetitive TMS was them administered (1 Hz) to either the left, right, or sham dorsolateral prefrontal cortex followed by repeat verbal and spatial n-back testing. Both pre and post stimulation visual evoked potentials (VEP) were examined for hemispheric differences and site (frontal/parietal). Results: Verbal WM exhibited rightward parietal hemispheric differences in VEP amplitude (p Conclusions: The observed dissociation between verbal and spatial working memory in the fronto-parietal network show that lateralization of VEPs can be exhibited and disrupted following unilateral TMS. Right stimulation caused an increase in the P3 during the spatial task, suggesting that there may be an increased allocation of frontal resources to complete the task. Additionally, the post-TMS change in laterality during the verbal task suggests a modulation of top-down control mechanisms within this network. Disclosure: Dr. Shields has nothing to disclose. Dr. Mock has nothing to disclose. Dr. Foundas has nothing to disclose.