Brain’s Left Hemisphere Helps Us Hear Through the Noise

by VR Sreeraman on Nov 15 2007 7:30 PM

A new study has found that the brain's left hemisphere is the reason why we are so good at picking up speech even in a noisy room.

The study, conducted by Hidehiko Okamoto and colleagues of the Institute for Biomagnetism and Biosignal analysis, Muenster, Germany, and colleagues in Japan and Canada, made the investigations using neuroimaging technique known as Magnetoencephalography (MEG).

The team used the technique to follow the underlying neural mechanisms and hemispheric differences related to simultaneous masking as volunteers listened to different combinations of test and background sounds.

In the study, test sounds were played either to the left or to the right ear, while the competing noise was presented either to the same or to the opposite ear.

By monitoring the brain's response to the different sound combinations, the researchers witnessed that the left hemisphere was the site of most neural activity associated with processing sounds in a noisy environment.

In daily lives, a person is exposed to many different sounds from multiple sources at the same time, from traffic noise to background chatter.

These noisy signals interact and compete with each other when they are being processed by the brain, a process called simultaneous masking.

The brain's response to masking stimuli brings about the 'cocktail-party effect' so that we are able to hear a particular sound, even in presence of a competing sound or background noise.

The study is published in the journal BMC Biology.