Entrainment of Task-Relevant Brain Oscillations in Visual Symmetry Detection and Contour Integration: Review and Ongoing Experimental Project

Visual perception relies on coordination of many distributed cortical regions that transform sensory data into coherent percepts. Among these regions, the parietal and occipital cortices are key in segregating target objects from background visual field and integrating their features into unified percepts. Oscillatory activity in the beta frequency range (~18 Hz) has been implicated in mediation of these two processes. The present study investigates the causal role of beta-band oscillations in visual segregation and integration via the use of transcranial alternating current stimulation (tACS) over bilateral parieto-occipital regions during contour integration and symmetry discrimination tasks. In a counterbalanced, within-subjects design, 18 Hz tACS is applied and resting-state EEG collected before and after stimulation. We hypothesise that 18 Hz tACS enhances performance during contour integration, but not during symmetry discrimination, with these effects relying on changes in resting-state beta power. The project is ongoing, and the current study analyses the preliminary results of the first nine participants, discussing their possible implications as well as theorising on possible discoveries when the data completion is completed. The project is useful in that it provides a framework for understanding how neural synchronisation supports perceptual organisation. It further demonstrates how non-invasive brain stimulation can test mechanistic hypotheses about cortical communication, bridging fundamental neuroscience and cognitive psychology.