“Insomnia is not a nighttime disorder,” said 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.”
The researchers found that the motor cortex in patients with chronic insomnia was more adaptable to change — more plastic — than in a group of people who slept well. They also found more “excitability” among neurons in the same region of the brain in the people with chronic insomnia.
“This adds evidence to the idea that insomniacs are in a constant state of heightened information processing that may interfere with sleep,” said the researchers.
For the study, the researchers used transcranial magnetic stimulation (TMS), which painlessly delivers electromagnetic currents to precise locations in the brain, which temporarily disrupts the function of the targeted area.
According to the researchers, “TMS is approved by the U.S. Food and Drug Administration to treat some patients with depression by stimulating nerve cells in the region of the brain involved in mood control.”
The study included 28 adults, including 18 who suffered from insomnia for a year or more and 10 who reported no trouble sleeping. Each person was outfitted with electrodes on their dominant thumb, as well as an accelerometer to measure the speed and direction of the thumb.
The researchers then gave each person 65 electrical pulses using TMS, stimulating areas of the motor cortex and watching for involuntary thumb movements linked to the stimulation. The researchers then trained each person for 30 minutes, teaching them to move their thumb in the opposite direction of the original involuntary movement. They then gave the electrical pulses again.
The idea was to measure the extent to which their brains could learn to move their thumbs involuntarily in the newly trained direction, the researchers explained. The more the thumb was able to move in the new direction, the more likely their motor cortexes could be identified as more plastic, they noted.
Because lack of sleep at night has been linked to decreased memory and concentration during the day, the researchers suspected that the brains of good sleepers could be more easily retrained. The results, however, were the opposite. They report that they found much more plasticity in the brains of those with chronic insomnia.
“The origins of the increased plasticity in insomniacs is unclear,” said Salas. “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,” she added.
Salas speculated it is possible that many of the problems linked to insomnia, such as increased metabolism, increased cortisol levels, and constant worrying, might be linked to increased plasticity in some way.
The researcher noted that TMS may play a role in diagnosing insomnia, as there is no objective test. Diagnoses are based solely on patient reports.
There also is not a single treatment that works for all people with insomnia, she said, adding that TMS could potentially prove to be a treatment, perhaps through reducing excitability.
The study was published in the journal Sleep.
Source: Johns Hopkins Medicine