Say you’re at a cocktail party with a friend, and the room is bustling with the bouncy noise of various conversations. Somehow your brain can siphon all that into a constant din and focus solely on what your friend is saying. “Not even the most sophisticated computer is capable of that,” said UO psychologist Mike Wehr.
“Our brain has some special hardware dedicated to that task. And we think we have discovered a small part of it.”
Wehr’s research team recently discovered that sound is processed by two different neuron channels in the brain: one for processing when a sound appears and the other for when it goes silent. In other words, there are neurons in the brain solely designated for registering the disappearance of sound, a specialization of neuron labor that scientists hadn’t previously known existed. “This is particularly important in understanding speech, because finding the beginning and ends of sounds is vital in chopping what’s said into meaningful components,” Wehr said.
Wehr believes the brain developed separate channels to more precisely differentiate the words in a conversation, which involves short sounds strung together with very brief pauses. It’s probably less necessary for dual channels like these to process, say, an opera singer holding a long, high note.
Wehr and two undergraduates made the discovery by monitoring the activity of the neurons and synapses in the brains of rats, which they bombarded with millisecond bursts of digitally created tones. Outside stimulation can excite neurons and make them “fire,” as Wehr puts it, or it can inhibit the neurons from reacting. When Wehr noticed certain neurons involved with hearing were only doing one or the other, it made him think there might be separate channels.
After a year of collecting data from the rats, he concluded that sound enters the ear, separates along two channels in the brain and then meets up at the auditory cortex, where the sound’s meaning is deciphered.
“The next step will be to test different parts of the pathway that sound takes through the brain, closer to the auditory cortex,” he said. “Down the road, I could foresee this line of research improving hearing aids that would accentuate discrete sounds with digital technology.”
These improved aids would sharpen the “edge” of sounds, the visual equivalent of drawing thick outlines around the shapes of a fuzzy image.
— Marc Dadigan
Mike Wehr will be among dozens of UO researchers whose labs will be located in the new Lewis Integrative Science Building, slated for completion in 2012. The facility will be home to a wide spectrum of brain research initiatives as well as green nanotechnology and solar energy. Visit iSci.uoregon.edu for more details.
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