Frequency-specific Transcranial Modulation of Oscillatory Dynamics in Visuospatial Attention Networks

Abstract

The ability to deploy neural resources to discrete stimulus features or groupings of features within the visual space is important to normative cognitive function. Population-level neural oscillatory activity across multiple frequencies and spatial locations has been linked to attentional deployment, but the inherent temporal dynamics of these neural oscillations have stymied efforts to image these responses in humans. Further, the impact of modulating neural activity in these networks on attentional performance remains unknown. Herein, we apply 2.0 mA transcranial direct current stimulation (tDCS) for 20 minutes over key nodes of the visual attention network (i.e., the visual and prefrontal cortices) using two opposite polarity current configurations, as well as a sham condition. Participants then performed an offline visuospatial discrimination task during concurrent recording with magnetoencephalography (MEG). Recordings were decomposed into time-frequency space and significant changes from baseline were identified and imaged. Time-series were then extracted from peak voxels for subsequent analysis, including functional connectivity analyses. Stimulation significantly altered behavioral performance in the attention task and basal activity in a polarity specific way, such that cathodal and anodal stimulation each affected the dynamics of attention circuits at distinct frequencies. Interestingly, the magnitudes of oscillatory neural responses at these frequencies were not significantly different between stimulation conditions, meaning that the tDCS-induced shifts in basal activity (i.e., baseline) carried through to the absolute amplitude of neural responses during attentional deployment. These findings shed light on the multi-spectral effects of tDCS on human neural circuits, particularly within and between prototypical attention network hubs.