How the Brain Dials Up the Volume to Hear Someone in a Crowd

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How the brain dials up the volume to hear someone in a crowd

Our brains have a remarkable ability to pick out one voice from among many. Now, a team of Columbia University neuroengineers has uncovered the steps that take place in the brain to make this feat possible. Today's discovery helps to solve a long-standing scientific question as to how the auditory cortex, the brain's listening center, can decode and amplify one voice over others -- at lightning-fast speeds. This new-found knowledge also stands to spur development of hearing-aid technologies and brain-computer interfaces that more closely resemble the brain.

These findings were reported today in Neuron.

"Our capacity to focus in on the person next to us at a cocktail party while eschewing the surrounding noise is extraordinary, but we understood so little about how it all works," said Nima Mesgarani, PhD, the paper's senior author and a principal investigator at Columbia's Mortimer B. Zuckerman Mind Brain Behavior Institute. "Today's study brings that much-needed understanding, which will prove critical to scientists and innovators working to improve speech and hearing technologies."

The auditory cortex is the brain's listening hub. The inner ear sends this brain region electrical signals that represent a jumble of sound waves from the external world. The auditory cortex must then pick out meaningful sounds from that jumble.

"Studying how the auditory cortex sorts out different sounds is like trying to figure out what is happening on a large lake -- in which every boat, swimmer and fish is moving, and how quickly -- by only having the patterns of ripples in the water as a guide," said Dr. Mesgarani, who is also an associate professor of electrical engineering at Columbia Engineering.

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