Inner ear problems may not just cause hearing issues but also fuel hyperactivity in children, researchers have found.

The study, conducted by the researchers at the Albert Einstein College of Medicine at Yeshiva University in New York City, found that inner-ear disorders can drive neurological changes characteristic to the behavioural abnormalities.

While behavioral problem, such as hyperactivity, is common among children and adolescents with severe inner-ea, the reason for association was not known until now.

“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,” study’s lead researcher Jean M. Hébert, professor in the Dominick P. Purpura Department of Neuroscience and of genetics at Einstein.

The study
For the purpose of the study, researchers took healthy mice and deleted Slc12a2, a gene responsible for mediating the transport of sodium, potassium, and chloride molecules in tissues, including the inner ear and central nervous system (CNS).

“To our surprise, it was only when we deleted the gene from the inner ear that we observed increased locomotor activity,” said Dr. Hébert.

Researchers concluded that inner-ear defects triggered abnormal functioning of the striatum, a central brain area responsible for controlling movement.

Researchers also found abnormally high levels of two proteins, pERK and pCREB. The two proteins are involved in a signaling pathway that controls the action of neurotransmitters.

To check if increased proteins levels caused the abnormal increase in locomotor activity, gene deficient mice were given injections of SL327, a pERK inhibitor. Researchers observed that these shots helped mice activity patterns to return to normal.

“Our study also raises the intriguing possibility that other sensory impairments not associated with inner-ear defects could cause or contribute to psychiatric or motor disorders that are now considered exclusively of cerebral origin,” said Dr. Hébert. “This is an area that has not been well studied.”

The findings of the study are published today in the online edition of Science.

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