Neural Mechanisms Underlying Selective Attention at a Cocktail Party

Our ability to selectively attend to a particular conversation amidst competing input streams (e.g. other speakers) epitomized by the ‘Cocktail Party’ problem, is remarkable. How this demanding perceptual feat is achieved from a neural systems perspective remains unclear and controversial. In this talk I will present data from both invasive and non-invasive electrophysiological recordings in humans, investigating the manner in which selective attention governs the brain’s representation of attended and ignored speech streams using a simulated ‘Cocktail Party’ Paradigm. Results indicate that brain activity dynamically tracks speech streams using both low frequency phase and high frequency amplitude fluctuations, and that optimal encoding likely combines the two. In and near low level auditory cortices, attention ‘modulates’ the representation by enhancing cortical tracking of attended speech streams, but ignored speech remains represented. In higher order regions, the representation appears to become more ‘selective’. Furthermore, when to-be-ignored input has a predictable rhythmic structure, there is even evidence for active suppression of responses to these stimuli, making attention more effective. Viewing the facial movements of the speaker movements of a speech further enhances the selectivity of the neural response. Together, these findings are a testament to the proactive and flexible nature of the neural system which dynamically shapes its internal activity according to environmental and contextual demands.