Study says brain can track voice in a crowded room
In a crowded room, paying attention to just one speaker's voice can be challenging.
Research in the Cell Press journal Neuron demonstrates how the brain hones in on one speaker to solve this "Cocktail Party Problem." Researchers discovered that brain waves are shaped so that the brain can selectively track the sound patterns from the speaker of interest and at the same time exclude competing sounds from other speakers. The findings could have important implications for helping individuals with a range of deficits such as those associated with attention deficit hyperactivity disorder, autism, and aging.
"In hearing, there is no way to 'close your ear,' so all the sounds in the environment are represented in the brain, at least at the sensory level," explains senior author Dr. Charles Schroeder, of Columbia University's Department of Psychiatry. "While confirming 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." In this way, when concentrating hard on such an "attended" speaker, one is barely, if at all, aware of ignored speakers.
Using direct recording of brain activity in surgical epilepsy patients, who were listening to natural spoken sentences, Dr. Schroeder and Dr. Elana Zion Golumbic, also of Columbia University, and their colleagues from New York University, University of Maryland, and Hillside-Long Island Jewish found two types of effects.
In and near the auditory cortex, brain signals reflect both attended and ignored speech, but attended speech generates higher signal amplitudes. However, in regions of the brain involved in "higher-order processing," such as language and attention, representation of attended speech was clear, while that of ignored speech was not detectable. Remarkably, the selective, higher-order representation is progressively refined as a sentence unfolds.
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