Enhancing visual motion discrimination by desynchronizing bifocal oscillatory activity
AUTHORS: Salamanca-Giron RF, Raffin E, Zandvliet SB, Seeber M, Michel C, Sauseng P, Huxlin KR, Hummel FC
NeuroImage, 240: 118299, October 2021
Visual motion discrimination involves reciprocal interactions in the alpha band between the primary visual cortex (V1) and mediotemporal areas (V5/MT). We investigated whether modulating alpha phase synchronization using individualized multisite transcranial alternating current stimulation (tACS) over V5 and V1 regions would improve motion discrimination. We tested 3 groups of healthy subjects with the following conditions: (1) individualized In-Phase V1 alpha -V5 alpha tACS (0°lag), (2 ) individualized Anti-Phase V1 alpha -V5 alpha tACS (180°lag) and (3) sham tACS. Motion discrimination and EEG activity were recorded before, during and after tACS. Performance significantly improved in the Anti-Phase group compared to the In-Phase group 10 and 30 min after stimulation. This result was explained by decreases in bottom-up alpha-V1 gamma-V5 phase-amplitude coupling. One possible explanation of these results is that Anti-Phase V1 alpha -V5 alpha tACS might impose an optimal phase lag between stimulation sites due to the inherent speed of wave propagation, hereby supporting optimized neuronal communication.