Abstract
Accumulating evidence has shown that frontal regions exert top-down control over the visual system to successfully prioritize processing of visual information. The communication-through-coherence theory (Fries, 2005) suggests that effective communication between anatomically distinct brain regions depends on the extent to which their oscillatory activity is synchronized. Indeed, it was shown that synchronization of alpha oscillations mediates frontal-occipital communication during attention allocation. However, how these distant regions communicate to determine visual performance had not been causally tested. Therefore, the goal of the current study was to causally test whether enhancing frontal-occipital synchronization of alpha oscillations would facilitate visual performance. To actively enhance frontal-occipital synchronization, we deployed a novel technique that combines electroencephalography (EEG) and non-invasive transcranial magnetic stimulation (TMS), (Zrenner et al., 2018). In a closed-loop procedure, TMS was delivered over the right frontal eye field (FEF) according to the phase of occipital alpha oscillations, measured in real time with scalp EEG. To evaluate the effect of stimulation, subjects underwent a classical visual detection-attention task, known to require the engagement of frontal and occipital regions, before and after the closed-loop procedure. In the task, subjects were required to detect a peripheral low contrast target that appeared after the onset of either a valid or neutral cue. Participants in a control condition completed the same task, without a closed-loop stimulation procedure. Preliminary results show that frontal-occipital closed-loop EEG-TMS enhanced visual sensitivity in the neutral condition relative to the control condition. Consistently, closed-loop stimulation over the right FEF induced greater right occipital alpha power suppression during the neutral cue condition. Furthermore, the magnitude of visual improvements was correlated with the accuracy of the occipital alpha phase estimation used to initiate the closed-loop stimulations. These results point to a causal relation between real-time modulation of frontal-occipital communication and enhanced visual perception.