Attentional inhibition by alpha power is modulated by faster theta rhythm and audio-visual congruency during natural speech perception

Abstract

AbstractAudio-visual processing is an essential aspect of human communication, however the mechanisms that underlie attention and processing in the auditory and visual domains are still limited. In order to understand how the brain attends to and processes information while ignoring irrelevant information, we employed a complex audio-visual paradigm to understand how the brain monitors and integrates audio-visual information in congruent and incongruent conditions. In three conditions, participants watched a Ted Talk presentation while listening to 1) congruent audio in both ears, 2) congruent audio in one ear and incongruent in the other (attending to congruent) or 3) congruent audio in one ear and incongruent audio in the other (attending to the incongruent). In order to investigate correlates of attention and audio-visual processing, we developed a novel method of detecting audio-visual congruency in the fluctuation rhythms of alpha power during each condition. Employing this method, we found that higher frequency alpha power fluctuation, falling in the delta-theta range, corresponded regionally to the side of attention, suggesting a novel mechanism of processing in that alpha-band activity may act as a temporal filter or attentional mechanism during audio-visual attention.