Prefrontal, parietal and basal activation associated with the reordering of a two-element list held in working memory.

A functional specialization in the prefrontal cortex along a dorsal-ventral gradient according to the type of processing in working memory, i.e. manipulation vs. maintenance, has been proposed based on previous neuroimaging studies. This seems particularly important for the further understanding of the functional architecture underlying working memory problems in patient populations. The current study examines the prefrontal involvement in the maintenance and manipulation of serial order of elements in working memory, with a task designed to be as simple as possible, to the aim of possible uses in clinical studies. Subjects held two-element ordered lists in memory and were presented with pseudo-random sequences of "reorder" and "maintain" cues. Reorder cues were found to be associated with activation in the dorsal prefrontal cortex, parietal cortex and the basal ganglia. The results show that the simple task was indeed sufficient to evoke the prefrontal activation of interest, add to the information on functional dorsal-ventral specialization in prefrontal cortex and provide support for a prefrontal-parietal monitoring-manipulation network.