10-Hz tACS up-regulates a visual attention network and down-regulates the rich club

Abstract

Abstract Synchronization of oscillatory brain activity may play a critical role in linking distributed neuronal populations into transient functional networks, with up-regulation of engaged networks during task performance accompanied by down-regulation of less salient networks. Can tACS be used to elicit network-specific changes in brain function, given that the distributed nodes of a network may experience varying amplitudes of exogenous current flow? We utilized MEG to characterize brain dynamics following bilateral parietal 10-Hz tACS during a visual attention task (8 healthy adults; 1 mA, verum/sham 20 min/30 s). Regions of interest included a cortico-cerebellar sensory processing network (SP: frontal, parietal, temporal cortex, hippocampus, cerebellum) and the Rich Club (bilateral superior parietal and frontal cortex, precuneus, hippocampus). Persistent changes in local oscillatory dynamics were seen in the SP network across a broad spectrum of frequency bands. Changes in alpha-band activity extended before, during, and after presentation of global/local letter images, consistent with a tonic influence of the 10-Hz tACS on alpha-band dynamics. Up-regulation of alpha and down-regulation of theta throughout the SP network was consistent with results seen in previous working memory studies. Moreover, increases in alpha were accompanied by increased gamma-band activity, consistent with a cross-frequency relationship between these rhythms. In contrast, down-regulation of alpha was characteristic of regions in Rich Club, with the exception of up-regulation in superior parietal cortex. Interestingly, despite a lack of consistency of a reciprocal relationship between alpha and theta in the Rich Club, the stimulation also reduced both theta and gamma-band activity, suggesting a role for theta-gamma coupling in the Rich Club. Our results suggest that tACS may provide a method for identifying and up-/down- regulating individual brain networks. Importantly, identifying tACS parameters that maximize changes to specific networks may be critical to increase efficacy and reduce potential negative side-effects of tACS. Research Category and Technology and Methods Basic Research: 8. Transcranial Alternating Current Stimulation (tACS) Keywords: tACS, MEG, Network, Visual Attention