How Your Brain Hears
London scientists are studying how the brain hears and hoping to use
this information to improve cochlear implants. Here's the press release.
~~~~~~~~~~~~~~~~~
Scientists at University College London and Imperial College London
have shown how the brain makes sense of speech in a noisy environment,
such as a pub or in a crowd. The research suggests that various regions
of the brain work together to make sense of what it hears, but that when
the speech is completely incomprehensible, the brain appears to give up
trying. The study was intended to simulate the everyday experience of
people who rely on cochlear implants, a surgically-implanted electronic
device that can help provide a sense of sound to a person who is
profoundly deaf or who has severe hearing problems.
Using MRI scans of the brain, the researchers, funded by the Wellcome
Trust and the Medical Research Council, identified the importance of one
particular region, the angular gyrus, in decoding distorted sentences.
The findings are published in the Journal of Neuroscience.
In an ordinary setting, where background noise is minimal and a
person's speech is clear, it is mainly the left and right temporal lobes
that are involved in interpreting speech. However, the researchers have
found that when hearing is impaired by background noise, other regions
of the brain are engaged, such as the angular gyrus, the area of the
brain also responsible for verbal working memory - but only when the
sentence is predictable.
"In a noisy environment, when we hear speech that appears to be
predictable, it seems that more regions of the brain are engaged,"
explains Dr Jonas Obleser, who did the research whilst based at the
Institute of Cognitive Neuroscience (ICN), UCL. "We believe this is
because the brain stores the sentence in short-term memory. Here it
juggles the different interpretations of what it has heard until the
result fits in with the context of the conversation."
The researchers hope that by understanding how the brain interprets
distorted speech, they will be able to improve the experience of people
with cochlear implants, which can distort speech and have a high level
of background noise.
"The idea behind the study was to simulate the experience of
having a cochlear implant, where speech can sound like a very distorted,
harsh whisper," says Professor Sophie Scott, a Wellcome Trust
Senior Research Fellow at the ICN. "Further down the line, we hope
to study variation in the hearing of people with implants - why is it
that some people do better at understanding speech than others. We hope
that this will help inform speech and hearing therapy in the
future."
