Inner-Ear Disorders Could Be Cause of Hyperactivity

Disorders like ADHD have traditionally been thought to originate exclusively in the brain, but new findings suggest that may not be the whole story. Scientists have observed that children and teens with inner-ear problems often have behavioral problems as well; however, no causal link has been established. New research from the Albert Einstein College of Medicine of Yeshiva University in New York may have uncovered an explanation for this co-occurrence of ear trouble and hyperactivity. Their findings indicate that inner-ear disorders are related to a genetic mutation that spurs hyperactive behavior. This could lead to new treatments for ADHD and more.

The research began when scientists noticed that some of their lab mice were unusually active—active to the point of chasing their tails. Further investigation into these hyperactive mice showed that they all had hearing disorders (deafness, inner-ear, or cochlear problems). The hyperactive mice also exhibited a mutation in the Slc12a2 gene, a gene also present in humans. To confirm that the gene was causing the hyperactivity, the researchers blocked the gene’s activity in a group of healthy mice. This resulted in increased activity in the formerly normal group.

The mutated gene was also linked with atypically high levels of two proteins, pERK and pCREB. To treat the problem, the researchers administered injections of haloperidol, a drug used to treat movement tics in humans, to the mice. The haloperidol counteracted the high protein levels and the mice’s activity levels normalized. These findings suggest a possible course of action for treating hyperactivity in humans, but more research is needed to be certain.

Lead scientist Professor Jean Hebert explained, “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. It certainly raises the issue that we ought to critically consider what contributes to the links between sensory impairments and specific behavior disorders.”

This research is published in the journal Science.

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