A genetic defect in the inner ear has been linked to hyperactivity, according to a study published last week in Science, leading researchers to believe that the condition, in some cases, can have a neurobiological root. Scientists removed a gene from young mice that caused inner-ear defects, including a loss of hearing, and found that the gene removal coincided with higher levels of two proteins in an area of the brain that regulates motor functions, resulting in hyperactive behavior.

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