In what is the largest study of its kind on insomnia, a research
group led by Daniel Buysse M.D., professor of psychiatry and clinical
and translational science, and the UPMC Professor of Sleep Medicine,
University of Pittsburgh School of Medicine, identified differences in
brain activity between states of sleep and wakefulness in 44 patients
diagnosed with insomnia and 40 good sleepers.
“While patients with insomnia often have their symptoms trivialized
by friends, families and even physicians, the findings in this study
add strong evidence to the emerging view that insomnia is a condition
with neurobiological as well as psychological causes,” said Dr. Buysse,
who is the senior author on the study. The study also shows that brain
activity during sleep is more nuanced than previously thought, with
different brain regions experiencing varying ‘depths’ of sleep.
The findings may help improve current treatments for insomnia such
as transcranial magnetic stimulation, and increase understanding of why
treatments such as mindfulness meditation are effective in some
patients.
Researchers used positron emission tomography (PET) scans during
which participants were injected with a solution of glucose molecules
tagged with a ‘tracer.’ Brain regions with higher activity took up a
proportionally higher amount of the radioactively tagged glucose and
were more metabolically active on the PET scans.
Data from the scans revealed relative activity differences in
specific brain regions between states of sleep and wakefulness in
patients with insomnia and good sleepers. The differences can be
attributed to either decreased activity during wakefulness or heightened
activity during sleep, the researchers report.
Dysfunction in the brain regions identified in the study may
correlate to specific symptoms in patients with insomnia, including
impairments in self-awareness and mood, memory deficits and rumination,
according to the authors.
Though the study design did not allow authors to discern whether
brain activity changes were the cause or consequence of insomnia, the
results do indicate that sleep is not uniform across different parts of
the brain, contradicting the prevailing view that the entire brain is
‘on’ while awake and ‘off’ while asleep. The study also refines results
from an earlier, similar study by researchers at the University of Pittsburgh Sleep Medicine Institute that had fewer participants.