Electrical stimulation of alpha oscillations stabilises performance on visual attention tasks
Cohen Kadosh R., Clayton M., Yeung N.
Neural oscillations in the alpha band (7–13 Hz) have long been associated with reductions in attention. However, recent studies have suggested a more nuanced perspective in which alpha oscillations also facilitate processes of cognitive control and perceptual stability. Transcranial alternating current stimulation over occipitoparietal cortex at 10 Hz (alpha-tACS) can selectively enhance EEG alpha power. To assess the contribution of alpha oscillations to attention, we delivered alpha-tACS across four experiments while 178 participants performed sustained attention tasks. Poor performance on all visual tasks was previously associated with increased EEG alpha power. We therefore predicted initially that alpha-tACS would consistently impair visual task performance. However, alpha-tACS was instead found to prevent deteriorations in visual performance that otherwise occurred during sham- and 50 Hz-tACS. This finding was observed in two experiments, using different sustained attention tasks. In a separate experiment, we also found that alpha-tACS limited improvements on a visual task where learning was otherwise observed. Consequently, alpha-tACS appeared to exert a consistently stabilising effect on visual attention. Such effects were not seen in an auditory control task, indicating specificity to the visual domain. We suggest that these results are most consistent with the view that alpha oscillations facilitate processes of top-down control and attentional stability.