Mystery of 'cocktail party' hearing solved

By Tanya Lewis, LiveScience 
The mystery of how the brain hones in on a single speaker in a noisy room may be solved, a new study shows. 

Studying the infamous " cocktail party problem," researchers found that brain waves are shaped to allow the brain to track the sounds it's interested in while ignoring competing sounds. The findings could be used to aid people with problems hearing or focusing on sounds, linked to  attention deficit hyperactivity disorder (ADHD), autism and aging, researchers reported March 6 in the journal Neuron.

Humans don't have a way of closing their minds to sounds, and so the brain "hears" everything that reaches a person's ears. The new study confirmed this.

"We also provide the first clear evidence that there may be brain locations in which there is exclusive representation of an attended speech segment, with ignored conversations apparently filtered out," senior author Charles Schroeder, a neuroscientist at Columbia University, said in a statement.

In the study, the researchers recorded the brain activity of epilepsy patients, who had recently undergone surgery, as they listened to natural spoken sentences. In order to figure out how the brain ignored or focused on various sounds, the researchersshowed the patients two side-by-side videos of people talking, and told them to pay attention to one of the speakers.

In the brain's auditory cortex, which processes incoming sound signals, the brain activity represented both the speech being attended to and that being ignored, but the attended speech had stronger signals.[ 10 Odd Facts About the Brain ]

In higher-level processing regions responsible for things like language and attention control, only the attended speech had a detectable, clear representation, the results showed. That representation became more refined as a sentence progressed, suggesting as a cocktail-party conversation continues, the brain focuses more and more only on those sentences while tuning out others.

Previous studies of the cocktail party problem have used simplified, unnatural sounds such as beeps or brief phrases, Schroeder said, whereas this study used natural speech.

The ability to study widespread patterns of brain activity in surgical epilepsy patients provides a link between work on a "brain activity map" in animals and uniquely human abilities like language and music, the researchers say.

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Comment author avatarJohn Schulienvia Facebook

Vision seems to work that way too. There is a window behind our TV couch, so when I am watching TV, I can see the reflection of the window on the screen. I've noticed that when I pay attention to the television program, the window disappears. When I deliberately notice the window, I can no longer perceive the television program.

    Reply#1 - Tue Mar 12, 2013 2:19 PM EDT
    Comment author avatartim maguire

    This is interesting news to me--because I can't filter out background noises. It all smushes together much the way different smells hit the nose. This works out well when one sound dominates. For instance, in movie theaters, I often can't hear those teenagers who are driving everyone else nuts. But if I am in a setting where there are several conversations going, I can't follow any of them and wind up a wallflower quietly trying not to look boring. In the car, I have to consciously listen to the radio and if I don't I may forget that it's on, it becomes part of the engine noise. Even if I'm listening to the music, I still don't hear the words unless actively trying (I hear the voice as an instrument, the words merely notes or musical phrases).

    My brother has the same problem so there appears to be a genetic element.

      Reply#2 - Tue Mar 12, 2013 4:56 PM EDT
      Comment author avatarFlounder sending Fan Mail

      This is not a new discovery. Selective auditory perception was proved back in early 1960s. Jerome Bruner testified to Congress about it in 1962. Robert Galambos, who discovered echolocation in bats, did seminal experiments on the subject. Here is is paper from 1975.

        Reply#3 - Tue Mar 12, 2013 8:12 PM EDT
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