“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, Ph.D., an associate professor in the department of psychiatry at the University of California, San Diego and secretary/treasurer of the Sleep Research Society.
“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.”
A research team led by Drummond and co-principal investigator Matthew Walker, Ph.D., studied 25 people with primary insomnia and 25 good sleepers. While most often insomnia occurs with another disorder, such as depression or chronic pain, primary insomnia is defined as a difficulty falling asleep or staying asleep in the absence of another condition, the researchers explain.
The study participants, who had an average age of 32, underwent a functional magnetic resonance imaging scan while performing a working memory task.
The study’s findings, published in the journal Sleep, show that participants with insomnia did not differ from good sleepers in objective cognitive performance on the task.
However, the MRI scans revealed that people with insomnia could not modulate activity in brain regions typically used to perform the task, according to the researchers.
As the task got harder, good sleepers used more resources within the working memory network of the brain, especially the dorsolateral prefrontal cortex, the study found. Those with insomnia, however, were unable to recruit more resources in these brain regions.
As the task got harder, those with insomnia did not dial down the “default mode” regions of the brain that are normally only active when our minds are wandering, the researchers noted.
“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.”