Behavioral abnormalities are traditionally thought to originate in the brain. But a new study by researchers at Albert Einstein College of Medicine of Yeshiva University, Bronx, NY, has found that inner-ear dysfunction can directly cause neurological changes that increase hyperactivity. The study, conducted in mice, also implicated two brain proteins in this process, providing potential targets for intervention. The findings were published in the September 6 edition of Science.

For years, scientists have observed that many children and adolescents with severe inner-ear disorders—particularly disorders affecting both hearing and balance—also have behavioral problems, such as hyperactivity. Until now, no one has been able to determine whether the ear disorders and behavioral problems are actually linked.

“Our study provides the first evidence that a sensory impairment, such as inner-ear dysfunction, can induce specific molecular changes in the brain that cause maladaptive behaviors traditionally considered to originate exclusively in the brain,” said study leader Jean M. Hébert, PhD, professor in the Dominick P. Purpura Department of Neuroscience and of genetics at Einstein.

The idea for the study arose when Michelle W. Antoine, a PhD student at Einstein at the time, noticed that some mice in Dr Hébert’s laboratory were unusually active— in a state of near-continual movement, chasing their tails in a circular pattern. Further investigation revealed that the mice had severe cochlear and vestibular defects and were profoundly deaf. The researchers established that the animals’ inner-ear problems were due to a mutation in a gene called Slc12a. This gene is also found in humans.

According to the researchers, the findings suggest that hyperactivity in children with inner-ear disorders might be controllable with medications that target biochemical pathways in a part of the brain called the striatum.

-Content provided by Hearing Review–