Inner-ear problems could be a cause of hyperactive behavior, research suggests. A study on mice, published in Science, said 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 study says.
Although the study's findings were "intriguing" they 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 behavioural problems.
However, no causal link has been found. The researchers in this study suggest inner-ear disorders lead to problems in the brain which then also affect behavior.
Another factor that could have some input is Gene mutation. 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.
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.
Prof Jean Hebert, the lead scientist, said: "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."
Anita Thapar, professor of child and adolescent psychiatry at Cardiff University's Institute of Psychological Medicine and Clinical Neurosciences, said it was an "intriguing study and set of findings".