Cortical network dynamics during verbal working memory function

This study is an exploratory investigation of the regional timing of cortic al activity associated with verbal working memory function. ERP activity wa s obtained from a single subject using a 124-channel sensor array during a task requiring the monitoring of imageable words for occasional targets. Di stributed cortical activity was estimated every 2.5 ms with high spatial re solution using real head, boundary element modelling of non-target activity . High-resolution structural MRI was used for segmentation of tissue bounda ries and co-registration to the scalp electrode array. The inverse solution was constrained to the cortical surface. Cortical activity was observed in regions commonly associated with verbal working memory function. This incl uded: the occipital pole (early visual processing); the superior temporal a nd inferior parietal gyrus bilaterally and the left angular gyrus (visual a nd phonological word processing); the dorsal lateral occipital gyrus (spati al processing); and aspects of the bilateral superior parietal lobe (imager y and episodic verbal memory). Activity was also observed in lateral and su perior prefrontal. regions associated with working memory control of sensor imotor processes. The pattern of cortical activity was relatively stable ov er time, with variations in the extent and amplitude of contributing local source activations. By contrast, the pattern of concomitant scalp topograph y varied considerably over time, reflecting the linear summation effects of volume conduction that often confound dipolar source modelling. (C) 2001 E lsevier Science B.V. All rights reserved.