UO neuroscientist glimpses how the brain transforms sound

The UO's Michael Wehr has observed one of the brain’s fundamental transformations of information.

When we hear a sound, the neurons in the lower region of the brain fire in sync with the sound’s rhythm, almost exactly encoding its original structure in the timing of their spikes, says Wehr, an associate professor of psychology in the UO’s Institute of Neuroscience.

“As the information progresses towards the auditory cortex, however, the representation of sound undergoes a transformation,” he said. “There is a gradual shift towards neurons that use an entirely different system for encoding information.”

Wehr and an undergraduate student — Xiang Gao, now a medical student at the Oregon Health & Science University — used a technique known as whole-cell recording in rats to capture the thousands of interactions that take place within a single neuron each time it responds to a sound. The team was able to observe how individual neurons in the rats responded to a steady stream of rhythmic clicks and watch cells communicate with each other.

Their observations provide a glimpse into how circuits deep within the brain give rise to our perception of the world. Neuroscientists previously had speculated that the translation of information in the brain might explain the perceptual boundary experienced between rhythm and pitch. Slow clicks sound rhythmic, Wehr said, but when they get fast enough, they sound like a buzzy tone. It could be that these different experiences of sound are produced by two different kinds of neurons in the brain, he said.

“The auditory system translates information into the same form used by the visual system,” Wehr said. “In the upper cortex of the brain, neurons use the same language to encode information.”

Neuroscientists theorize that a shared language among neurons in the upper cortex could support multisensory integration, helping us make decisions by putting together what we see and what we hear.

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— By Andrew Stiefel, Office of the Vice President for Research and Innovation