Emergence of neural encoding of auditory objects while listening to competing speakers

TLDR

Auditory scene analysis has been conceptualized similarly to visual object perception, but the neural mechanisms underlying this process remain unclear. The study aimed to investigate how the brain encodes competing auditory objects while subjects selectively listened to one of two speakers. Magnetoencephalography was used to record neural activity as participants listened to two competing speakers of either the same or different sex. The MEG data revealed distinct, phase‑locked neural representations for each speaker, with the attended stream dominating posterior auditory cortex responses around 100 ms and showing intensity‑specific adaptation, demonstrating that overlapping auditory objects are encoded separately and support top‑down attention and bottom‑up adaptation.

Abstract

A visual scene is perceived in terms of visual objects. Similar ideas have been proposed for the analogous case of auditory scene analysis, although their hypothesized neural underpinnings have not yet been established. Here, we address this question by recording from subjects selectively listening to one of two competing speakers, either of different or the same sex, using magnetoencephalography. Individual neural representations are seen for the speech of the two speakers, with each being selectively phase locked to the rhythm of the corresponding speech stream and from which can be exclusively reconstructed the temporal envelope of that speech stream. The neural representation of the attended speech dominates responses (with latency near 100 ms) in posterior auditory cortex. Furthermore, when the intensity of the attended and background speakers is separately varied over an 8-dB range, the neural representation of the attended speech adapts only to the intensity of that speaker but not to the intensity of the background speaker, suggesting an object-level intensity gain control. In summary, these results indicate that concurrent auditory objects, even if spectrotemporally overlapping and not resolvable at the auditory periphery, are neurally encoded individually in auditory cortex and emerge as fundamental representational units for top-down attentional modulation and bottom-up neural adaptation.