How your brain stays focused on conversations in a noisy room
The brain processes voices differently depending on the volume of the speaker and if the listener is focused on them
By Jason Arunn Murugesu
6 June 2023
Mechanisms in the brain help us pick out speech in a crowd
Zuckerman Institute, Columbia University (2023)
We now have a good explanation for how our brain keeps track of a conversation while we are in a loud, crowded room, a discovery that could improve hearing aids.
The general idea for speech perception is that only the voice of the person you are paying attention to gets processed by the brain, says Vinay Raghavan at Columbia University in New York. “But my issue with that idea is that when someone shouts in a crowded place, we don’t ignore it because we’re focused on the person we’re talking to, we still pick it up.”
To better understand how we process multiple voices, Raghavan and his colleagues implanted electrodes into the brains of seven people to monitor the organ’s activity while they underwent surgery for epilepsy. The participants, who were awake throughout the surgery, listened to a 30-minute audio clip of two voices.
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During the half-hour period, the participants were repeatedly asked to change their focus between the two voices, one of which belonged to a man and the other to a woman. The voices spoke over each other and were largely the same volume, but, at various points in the clip, one was louder than the other, mimicking the changing volumes of background conversations in a crowded space.
The team then used this brain activity data to produce a model that predicted how the brain processes the quieter and louder voices and how that might differ depending on which voice the participant was asked to focus on.
The researchers found that the louder of the two voices was encoded by both the primary auditory cortex, which is thought to be responsible for the conscious perception of sound, and the secondary auditory cortex, responsible for more complex sound processing, even if the participant was told not to focus on the louder voice.
