fMRI Study Deciphers Insomnia’s Wandering Mind

It’s well known that people with insomnia can have trouble concentrating during the day. A new brain imaging study may help explain why.

“We found that insomnia subjects did not properly turn on brain regions critical to a working memory task and did not turn off ‘mind-wandering’ brain regions irrelevant to the task,” said Sean P.A. Drummond, PhD, lead author. “Based on these results, it is not surprising that someone with insomnia would feel like they are working harder to do the same job as a healthy sleeper.”

The researchers studied 25 people suffering from primary insomnia and 25 normal sleepers, with the average age of 32 years. The study subjects underwent a functional magnetic resonance imaging (fMRI) scan at the same time as performing a working memory task.

Dorsolateral Prefrontal Cortex Differences

The results show that participants with insomnia had no difference from the good sleepers in objective cognitive performance on the working memory task. Yet the MRI scans showed that people with insomnia could not adjust activity in brain regions typically used to perform the task.

As their task grew harder, good sleepers employed more resources in the brain’s working memory network, especially the dorsolateral prefrontal cortex. Insomnia subjects, however, were unable to conscript more resources in these brain regions. Additionally, as the task got harder, participants with insomnia did not dampen the “default mode” regions of the brain that are usually only active when our minds are wandering.

Daytime Problems

“The data help us understand that people with insomnia not only have trouble sleeping at night, but their brains are not functioning as efficiently during the day,” said Drummond. “Some aspects of insomnia are as much of a daytime problem as a nighttime problem. These daytime problems are associated with organic, measurable abnormalities of brain activity, giving us a biological marker for treatment success.”

This study, According to the authors, is the biggest to look at cerebral activation with fMRI during cognitive performance in people with primary insomnia, in comparison to well-matched good sleepers. It is the first also, to describe functional MRI differences in working memory in people with primary insomnia.

Around 10 to 15 percent of adults have an insomnia disorder with distress or daytime impairment, says The American Academy of Sleep Medicine. Usually insomnia occurs with another problem like depression or chronic pain, or is caused by a medication or substance. Fewer people suffering from insomnia are considered to have primary insomnia, defined as a difficulty falling asleep or maintaining sleep in the absence of a coexisting condition.

Reference:

Drummond SPA; Walker M; Almklov E; Campos M; Anderson DE; Straus LD.
Neural correlates of working memory performance in primary insomnia..
SLEEP, 2013;36(9):1307-1316