Reacting to Sound: How the Left and Right Brain Differ
It’s been over 150 years since French physician Paul Broca announced that the left hemisphere of the brain dominates language processing over the right, and researchers still don’t understand why this is. Now, a team of researchers from The City College of New York have started to unravel the mystery.
The scientists, including Professor Hysell Oviedo (CCNY, The Graduate Center), research associate Robert Levy, postdoctoral fellow Tiemo Marquarding, former research associate Ashlan Reid, and former undergrad researcher Christopher Pun, discovered features of certain brain circuits that could explain Broca’s discovery. Besides solving a scientific question, this could also help researchers understand the wiring in the brains of people with disorders such as autism or schizophrenia.
In the study published in Nature Communications, the researchers observed the brains of mice as the mice reacted to different types of sound, using an array of tools like 3D whole-brain imaging and electrophysiology. Differences between the left and right sides began to surface.
“The left auditory cortex emerged as a specialist, wired to detect specific tone sequences,” Oviedo said, “whereas the right auditory cortex is a generalist, wired to detect any tone sequence.”
Now that they’ve uncovered the wiring diagram for auditory communication, Oviedo said, researchers can start to dig into how these circuits develop on a molecular level and figure out what goes wrong in communication disorders.
“Although the causes of communication deficits vary, the underlying pathological mechanism routinely involves miswiring of the connections between neurons in the language centers of the brain,” Oviedo said. A shift from left- to right-hemisphere dominance of language processing is characteristic of autism spectrum disorder, for example. The paper also notes that abnormal specialization of language processing between the left and right is a risk factor for schizophrenia.