The neural basis of the central executive system of working memory

Abstract

Working memory refers to a system for temporary storage and manipulation of information in the brain, a function critical for a wide range of cognitive operations. It has been proposed that working memory includes a central executive system (CES) to control attention and information flow to and from verbal and spatial short-term memory buffers. Although the prefrontal cortex is activated during both verbal and spatial passive working memory tasks, the brain regions involved in the CES component of working memory have not been identified. We have used functional magnetic resonance imaging (fMRI) to examine brain activation during the concurrent performance of two tasks, which is expected to engage the CES. Activation of the prefrontal cortex was observed when both tasks are performed together, but not when they are performed separately. These results support the view that the prefrontal cortex is involved in human working memory.

Brain imaging of the central executive component of working memory

“…Moreover, they also indicate that similar prefrontal areas are activated by tasks requiring executive processes which at a first sight are quite different. For example, the middle prefrontal gyrus (BA 9/46) was found in manipulation [30,40,98] and updating [103,124] tasks as well as in dual-task coordination [39], inhibition processes [26,31] and shifting processes [102]. Furthermore, the activity of that region was directly linked to the memory load, as demonstrated by Braver et al [17] and Cohen et al [28] using parametric design studies.…”

“…The first neuroimaging study which explored dual-task coordination was that of D'Esposito et al [39]. Participants were administered two tasks predominantly involving posterior brain regions and requiring no storage in working memory: a semantic judgement task (to identify exemplars of a target category in series of orally presented words) and a spatial-rotation task (to indicate which of two squares had a dot in the same location, relative to a double line, as a spatially rotated target square).…”

“…In summary (see Table 5), all these studies except that by D'Esposito et al [39] demonstrated that dual-task coordination (that participants have or have not to store the items in short-term memory) is not dependent upon a specific prefrontal area but rather involves interplay of various specialized information-processing systems. For example, the study by Adcock et al [1] used the same tasks as D'Esposito et al [39] and found no specific prefrontal areas during the execution of the dual-task paradigm.…”

“…For example, the study by Adcock et al [1] used the same tasks as D'Esposito et al [39] and found no specific prefrontal areas during the execution of the dual-task paradigm. Although the reason for these discrepancies is not really clear, one explanation proposed by Klingberg [65] is that activation of the dorsolateral prefrontal and cingulate cortex found by D'Esposito et al [39] are not specific to dual-task performance and could be due to an increase in working memory demand caused by the simultaneous performance of two non working-memory tasks. For example, it cannot be excluded that the stimulus processing or response in one task is delayed while the other task is given priority, thus inducing a working memory requirement that does not exist in the single task condition.…”

Task-order coordination in dual-task performance and the lateral prefrontal cortex: an event-related fMRI study

“…The findings of these previous imaging studies suggested a specific role of the lateral prefrontal cortex (LPFC) for dual-task processing (D'Esposito, Detre, Alsop, Shin, Atlas, & Grossman, 1995;Goldberg et al, 1998;Schubert & Szameitat, 2003; but see Jiang, Saxe, & Kanwisher, 2004). Specifically, these studies compared the fMRI activation in dual-task blocks with the activation when participants performed the component tasks in single-task blocks, thereby employing the method of cognitive subtraction (Friston, Price, Fletcher, Moore, Frackowiak, & Dolan, 1996).…”