Sleep Loss and Circadian Clock Have Different Effects on Brain Regions

New research has emerged that maps the effects the circadian clock has on different regions of the brain.  The new study shows:

  • How the brain can keep up performance throughout the day
  • Why there is so much waxing and waning of symptoms in psychiatric and neurodegenerative diseases
  • Why it is necessary that we avoid negotiations that lead long into the night
  • Peak activity assessed on brain imaging varies by region in the brain, and those regions are affected differently depending on sleep loss and time of day (circadian rhythm)
  • Implications for understanding how our internal time of day and circadian rhythms affect the brain

Results help scientists understand why shift work and people who work long hours have a hard time concentrating and paying attention on the job, especially in the early morning hours.

What happens inside the brain when you are awake for 36-48 hours before you can get some shut-eye?  A new study, which was published in Science, looked at the scans of 33 brains over a 2-day period of sleep deprivation, which was then followed by recovery sleep.  This research was done out of the University of Liege and University of Surrey.  Several brain regions were identified with activity on the scans, especially in the subcortical areas.  All of these regions followed a 24-hour pattern of rhythm with a timing that varied across each of the regions.

Other areas of the brain, such as the frontal brain region, had less activity with awake time after a return to pre-deprivation levels following the sleep recovery.  Some of the regions showed a combination between a decline linked to wakefulness and a rhythmic pattern.

Additionally, researchers found that the sleep-loss associated brain activity effects were more widespread and broad when participants performed simple tasks like reaction time, instead of harder memory-reliant tasks.

There were 13 brain scans obtained in each participant.  Twelve scans were taken during sleep deprived periods and one was taken during sleep recovery.  The data were compared to the melatonin rhythm, which is the human brain’s circadian pacer.

These findings, including the prominent circadian rhythm component of the brain responses, gives scientists greater understanding of the complex mechanisms of the brain’s function and activity as a result of sleep loss.  Researchers also note that they have found that the time of day the scans were taken made a big difference in the pictures they get as well.

It has long been suggested that wakefulness duration and internal time of day (circadian rhythm) affects the brain’s function.  Performance does not linearly deteriorate during periods of sleep deprived states when compared to functioning while awake.  Performance is a constant throughout the day, rapidly deteriorating during the internal nighttime, but improving slightly upon waking.

These two processes can be seen on functional MRI, which is an imaging study that can measure brain activity.  Furthermore, these findings indicate that the contribution of sleep deprivation and effects of internal time vary in different brain regions.

Researchers note that it is interesting to see that the circadian rhythm and sleep deprivation have such a profound impact on the brain’s function, which can be seen and monitored on imaging studies.  This may help researchers in understanding how brain performance is maintained throughout the day, why psychiatric and neurodegenerative symptoms seem to wax and wane, and why it is so hard to stay focused in the morning after a night without sleep.

These findings will highlight the complicated communication and link between the awake time and our biological clocks on a more widespread regional brain level.


 Rachael Herman is a professional writer with an extensive background in medical writing, research, and language development. Her hobbies include hiking in the Rockies, cooking, and reading.


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