Behavioral problems are often blamed on the brain, but the inner ear could play a vital role.
Researchers found inner-ear dysfunction could be linked to hyperactivity, an Albert Einstein College of Medicine at Yeshiva University press release reported.
Scientists have noticed that children with inner-ear problems, especially ones affecting hearing and balance, are more prone to hyperactivity.
Inner-ear disorders are usually genetic, but can be caused by certain types of injuries.
"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 leader Jane M. Hébert, professor at the Dominick P. Purpura Department of Neuroscience and of Genetics at the Albert Einstein College of Medicine, said.
The idea was born when Michelle W. Antoine, a Ph.D. student at Einstein, noticed some mice were hyperactive to the point where they almost never stopped moving. Upon investigation, researchers discovered all of the unusually hyper mice were deaf, and had cochlear (the part of the ear responsible for hearing) and vestibular (responsible for balance) defects.
"We then realized that these mice provided a good opportunity to study the relationship between inner-ear dysfunction and behavior," Dr. Hébert, said.
The researchers were also able to find the root of the mice's problems, a mutation in a gene called Slc12a2, which "ediates the transport of sodium, potassium, and chloride molecules in various tissues, including the inner ear and central nervous system (CNS)," the press release reported.
Scientists "deleted" the gene from the part of the brain responsible for movement control, the mice in this part of the study were healthy.
"To our surprise, it was only when we deleted the gene from the inner ear that we observed increased locomotor activity," Dr. Hébert, said.
The research team concluded that the ear defects caused abnormalities in the central brain area responsible for movement called the striatum.
The research suggests children suffering from inner-ear-related hyperactivity could one day control their condition with medications.
"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," Dr. Hébert, said. "This is an area that has not been well studied."
