Mechanisms Underlying Selective Neuronal Tracking of Attended Speech at a Cocktail Party

The ability to focus on and understand one talker in a noisy social environment is a critical social-cognitive capacity, whose underlying neuronal mechanisms are unclear. We investigated the manner in which speech streams are represented in brain activity and the way that selective attention governs the brains representation of speech using a Cocktail Party paradigm, coupled with direct recordings from the cortical surface in surgical epilepsy patients. We find 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, in that there is no detectable tracking of ignored speech. This selectivity itself seems to sharpen as a sentence unfolds. º Both low-frequency phase and high-gamma power preferentially track attended speech º Near auditory cortex attention modulates response to attended and ignored speakers º Selective tracking of only the attended talker increases in higher-order regions º Selectivity for the attended speaker increases over time Zion Golumbic et al. use direct brain recordings in surgical epilepsy patients to investigate how people attend one speaker in noisy social environments. Neuronal activity dynamically tracks an attended speaker, with increasing selectivity in higher-order regions, as a sentence unfolds.