Cortical mechanisms of auditory object detection in listeners with and without hearing loss

Daily life communication requires listeners to parse meaningful auditory stimuli from other ongoing sounds and background noise. This process relies on the ability to detect sounds with regular acoustic features, forming “auditory objects.” Hearing loss impairs auditory object formation, even with hearing assistive technology such as hearing aids or cochlear implants, suggesting that certain brain mechanisms may be at play. To better understand the brain mechanisms underlying auditory object detection, two studies investigated neural and behavioral responses in listeners with and without hearing loss. In these two studies, a tone cloud stimulus was used, composed of multiple tones with a random frequency distribution, constituting the noise. When several of these tones become coherent across the frequency dimension, an “auditory object” will pop out from the background. Participants with different hearing configurations were recruited, including age-typical hearing, cochlear implant users, and hearing aid users. The task required detecting auditory objects, while brain responses were recorded using electroencephalography. Across the two studies, cochlear implant users had the worst detectability of the auditory objects. Brain responses showed that cochlear implant users did not exhibit a “phase-locked” response to object emergence, a phenomenon that requires cortical activity synchrony. However, when looking at “non-phase-locked” responses, all listeners showed oscillatory responses in the alpha and beta frequency bands. The magnitude of these responses did not differ across listeners. Clinically, this work highlights the value of targeting auditory object detection in rehabilitation by designing training protocols that enhance oscillatory responses.