Inner-ear problems may be a cause of hyperactivity behavior, according to a report released Thursday.
A study on mice, published in Science claimed that such problems caused changes in the brain that led to hyperactivity. It could lead to the development of new targets for behavior disorder treatments, the US team of researchers said. A UK expert said the study's findings were "intriguing" and should be investigated further.
Behavioral problems such as ADHD are usually thought to originate in the brain but scientists have observed that children and teenagers with inner-ear disorders - especially those that affect hearing and balance - often have behavioral problems as well. However, no causal link has been found.
The researchers suggest inner-ear disorders lead to problems in the brain which then also affect behavior. The team from the Albert Einstein College of Medicine of Yeshiva University in New York noticed some mice in the lab were particularly active - constantly chasing their tails.
They were found to be profoundly deaf and have disorders of the inner ear - of both the cochlea, which is responsible for hearing, and the vestibular system, which is responsible for balance. The researchers found a mutation in the Slc12a2 gene, also found in humans. Blocking the gene's activity in the inner ears of healthy mice caused them to become increasingly active.
The researchers then examined the striatum, an area in the center of the brain area that controls movement. They found higher-than-normal levels of two proteins, pERK and pCREB. Mice with the gene flaw were given injections of haloperidol, a medicine already used to treat tics - uncontrollable movement - in humans.
It was seen to counteract the high protein levels, and mouse activity patterns returned to normal. The researchers suggest the same process could be targeted in people, and that medications could be developed to help manage hyperactivity in children with inner-ear disorders.
