Insomnia doesn't feel like a good thing, though. . .

Johns Hopkins researchers report that people with chronic insomnia show more plasticity and activity than good sleepers in the part of the brain that controls movement.

"Insomnia is not a nighttime disorder," says study leader Rachel E. Salas, M.D., an assistant professor of neurology at the Johns Hopkins University School of Medicine. "It's a 24-hour brain condition, like a light switch that is always on. Our research adds information about differences in the brain associated with it."

Because lack of sleep at night has been linked to decreased memory and concentration during the day, Salas and her colleagues suspected that the brains of good sleepers could be more easily retrained. The results, however, were the opposite. The researchers found much more plasticity in the brains of those with chronic insomnia.

Salas says the origins of increased plasticity in insomniacs are unclear, and it is not known whether the increase is the cause of insomnia. It is also unknown whether this increased plasticity is beneficial, the source of the problem or part of a compensatory mechanism to address the consequences of sleep deprivation associated with chronic insomnia. Patients with chronic phantom pain after limb amputation and with dystonia, a neurological movement disorder in which sustained muscle contractions cause twisting and repetitive movements, also have increased brain plasticity in the motor cortex, but to detrimental effect.