The drug -- rapamycin -- reversed brain dysfunction caused by a genetic disease called tuberous sclerosis complex, or TSC. Because half of TSC patients also suffer from autism, the findings offer new hope for addressing learning disorders due to autism.

The University of California-Los Angeles researchers studied mice bred with TSC and verified the animals suffered from the same severe learning difficulties as human patients -- half of whom also suffer from autism. The researchers traced the learning problems to biochemical changes sparking abnormal function in the brain structure -- the hippocampus -- that plays a role in memory. After three days of treatment, TSC mice learned as quickly as healthy mice.

"These findings challenge the theory that abnormal brain development is to blame for mental impairment in tuberous sclerosis," first author Dan Ehninger said in a statement. "Our research shows that the disease's learning problems are caused by reversible changes in brain function -- not by permanent damage to the developing brain."

The study is published in the Nature Medicine online.