The Causal Role of Alpha Oscillations in Selection

Abstract

Alpha oscillations, or brain waves with a frequency between 8-12 Hz, are a neural correlate of attentional selection. Correlational studies show increases and decreases in alpha-band activity are associated with the suppression of irrelevant information and processing of relevant information respectively, but it is unclear how alpha oscillations relate specifically to these distractor suppression and target enhancement mechanisms. We manipulated alpha levels in the posterior parietal cortex with transcranial alternating current stimulation (tACS) while participants completed a color change detection task with a variable number of distractors and targets. Our results showed that alpha tACS enhanced working memory capacity in a distractor-absent condition while having no effect in distractor-present conditions. Alpha tACS also had no effect on modulating distractor filtering ability. This contributes causal evidence that alpha supports target enhancement, not distractor suppression, in the debate about alpha’s role in attention.