Turn down the noise!

Hearing relies on a complex set of circuits within the brain to process information from the ear. As we age, it becomes harder for humans to understand speech when we’re in a noisy environment – say, at a party.

Hearing researcher Brett Schofield, Ph.D., professor of anatomy and neurobiology, is on a mission to discover why, and a multi-million-dollar grant from the National Institutes of Health will allow him to use state-of-the-art technology to advance understanding.

Dr. Schofield explains that cholinergic circuits, formed by brain cells that use acetylcholine to communicate with other brain cells, play a key role in many aspects of hearing, including selective attention, learning, and understanding speech in a noisy environment. Cholinergic circuits help the brain adapt during development, during aging and in response to damage of the ear or the brain.

However, scientists’ understanding is hindered by several key gaps in knowledge about cholinergic circuits, says Dr. Schofield. The National Institute on Deafness and Other Communication Disorders/NIH will provide him $619,000 for the first year of a new award to study hearing circuits in the brains of rodents. The total expected amount of funding for the five-year project, “Modulatory Circuits in the Auditory System,” is nearly $3 million.

Dr. Schofield lays out the steps he’ll take:

1. Identify the brain cells that give rise to specific cholinergic circuits that are associated with hearing.
2. Identify the extent to which those brain cells have nerve fibers that branch so that they can affect multiple brain regions simultaneously. Such branching may be key for efficient processing of sounds.
3. Identify the types of molecules that the cholinergic circuits activate in the brain cells they target. This is essential for understanding their function and identifying potential sites for therapy.
4. Identify the cholinergic circuits that higher brain centers use to modulate sound processing by brainstem circuits. “This aspect appears to be especially important for understanding speech in a noisy environment, a task that becomes increasingly difficult for many of us as we get older,” says Dr. Schofield.

Overall, he adds, ”Our results will provide fundamental information about brainstem cholinergic circuits, their targets within the brain, and the extent to which they may be activated by projections from higher brain centers. We hope that our results help show the way toward the prevention and treatment of hearing problems.”