Abstract
Working memory (WM) is one of the most studied cognitive constructs. Although many neuroimaging studies have identified brain networks involved in WM, the time course of these networks remains unclear. In this paper we use dense-array electroencephalography (dEEG) to capture neural signals during performance of a standard WM task, the n-back task, and a blend of principal components analysis and independent components analysis (PCA/ICA) to statistically identify networks of WM and their time courses. Results reveal a visual cortex centric network, that also includes the posterior cingulate cortex, that is active prior to stimulus onset and that appears to reflect anticipatory, attention-related processes. After stimulus onset, the ventromedial prefrontal cortex, lateral prefrontal prefrontal cortex, and temporal poles become associated with the prestimulus network. This second network appears to reflect executive control processes. Following activation of the second network, the cortices of the temporo-parietal junction with the temporal lobe structures seen in the first and second networks re-engage. This third network appears to reflect activity of the ventral attention network involved in control of attentional reorientation. The results point to important temporal features of network dynamics that integrate multiple subsystems of the ventral attention network with the default mode network in the performance of working memory tasks.
Highlights
An essential capacity for cognition and human performance is working memory (WM), the ability to hold information in store as it is manipulated through various cognitive transformations
Results from fMRI research are consistent with this interpretation that there is local priming of visual cortex when the representation of a visual stimulus is held in a perceptual store
Consistent with the interpretation that a greater priming negativity (SPN) reflects greater anticipatory attention, the amplitude of Component 1 (C1) in the present study varied with response time (RT), with larger C1s and faster responses for the low load vs. high load, and for the location vs. color conditions
Summary
An essential capacity for cognition and human performance is working memory (WM), the ability to hold information in store as it is manipulated through various cognitive transformations. The n-back task, which has been in use at least since 1958 (Kirchner, 1958), can accommodate working load manipulations and different stimulus features. This property allowed it to be used to study WM across various sensory modalities, and a number of early fMRI studies used n-back tasks to isolate and compare the neural mechanisms for maintaining and manipulating items in WM. Not developed to isolate component processes of WM (see Jaeggi et al, 2010), the body of evidence that has developed through the use of the n-back task is impressive, in the sheer number of published studies and in what it has revealed about brain regions and networks responsible for WM. Nothing is known about the time course(s) of these brain regions and networks in WM
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