Attention shift in human verbal working memory: Priming contribution and dynamic brain activation

When multiple items in working memory need to be accessed and manipulated, the internal attention should switch between them and, this switching process is time consuming (H. Garavan. Serial attention within working memory. Mem. Cognit. 26 (1998) 263-276). However, it is not clear how much of this switching cost is due to the existence or absence of the stimulus identification priming. With a figure identification and counting task, we demonstrate a small but significant priming contribution to this attention-switching cost. Furthermore, through 64-channel event-related potential (ERP) recordings, we found two ERP correlates (at 280 ms and 388 ms) of this internal attention-switching function. Source localization analysis shows dynamic brain activation starts from the temporal-occipital region and finishes in the left prefrontal cortex. The occipital-prefrontal and cingulate-prefrontal co-activations were orderly observed. We discuss the present ERP results along with our previous fMRI findings and suggest a dominant role of the left prefrontal cortex associated with attention shifts in verbal working memory.