Enhancing visual motion discrimination by desynchronizing bifocal oscillatory activity

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 degrees lag), (2) individualized Anti-Phase V1(alpha)-V5(alpha)tACS (180 degrees 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.

Automated summary

This study investigated the effects of individualized multisite transcranial alternating current stimulation on visual motion discrimination. The results indicated that Anti-Phase stimulation led to better improvement in motion discrimination compared to In-Phase stimulation, possibly due to a decrease in bottom-up alpha-V1 gamma-V5 phase-amplitude coupling.