Abstract
Neuronal activity in sensory and fronto-parietal (FP) areas underlies the representation and attentional control, respectively, of sensory information maintained in visual working memory (VWM). Within these regions, beta/gamma phase-synchronization supports the integration of sensory functions, while synchronization in theta/alpha bands supports the regulation of attentional functions. A key challenge is to understand which mechanisms integrate neuronal processing across these distinct frequencies and thereby the sensory and attentional functions. We investigated whether such integration could be achieved by cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography, we found that CFS was load-dependently enhanced between theta and alpha-gamma and between alpha and beta-gamma oscillations during VWM maintenance among visual, FP, and dorsal attention (DA) systems. CFS also connected the hubs of within-frequency-synchronized networks and its strength predicted individual VWM capacity. We propose that CFS integrates processing among synchronized neuronal networks from theta to gamma frequencies to link sensory and attentional functions.
Highlights
Working memory (WM) has a limited capacity of 3À4 objects (Luck and Vogel, 1997) and is comprised of sensory storage and central executive control for manipulating the stored information and supporting the preparation of a contingent response (Baddeley, 1996; Miller and Cohen, 2001; Sreenivasan et al, 2014)
We assessed here the functional role of cross-frequency phase synchrony (CFS) in visual WM (VWM) by analyzing magneto- and electroencephalography (M/EEG) data acquired during a delayed match-to-sample VWM task (Luck and Vogel, 1997; Palva et al, 2010, 2011), which had earlier revealed concurrent large-scale 1:1 synchronization in a, b, and g-frequency bands (Palva et al, 2010)
We found that CFS was correlated with task demands, predicted individual VWM capacity and connected 1:1-within-frequency synchronization among task-relevant visual and fronto-parietal regions
Summary
Working memory (WM) has a limited capacity of 3À4 objects (Luck and Vogel, 1997) and is comprised of sensory storage and central executive control for manipulating the stored information and supporting the preparation of a contingent response (Baddeley, 1996; Miller and Cohen, 2001; Sreenivasan et al, 2014). During visual WM (VWM) maintenance, these functions are achieved in visual and fronto-parietal (FP) brain areas, which exhibit enhanced neuronal activity levels during memory maintenance in both monkey single- and multi-unit recordings (Buschman et al, 2011; Goldman-Rakic, 1995; Siegel et al, 2009) and functional MRI (fMRI) of humans (Munk et al, 2002; Pessoa et al, 2002; Todd and Marois, 2004). While the visual cortex is responsible for the processing of visual information and its maintenance in VWM (Riggall and Postle, 2012; Emrich et al, 2013; Kravitz et al, 2013), lateral prefrontal cortex (LPFC) is thought to regulate VWM maintenance, represent goals and rules, and govern response selection (Miller and Cohen, 2001; Rowe et al, 2000; Sreenivasan et al, 2014; Markowitz et al, 2015). Macaque cortical recordings have shown that in beta- (b, 15–30 Hz) and gamma- (g, 30À90 Hz) frequency bands, inter-areal PS is enhanced by the maintenance of visual
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