New research has shown that normal human brain temperature varies much more than we thought, and this could be a sign of healthy brain function. In healthy men and women, where oral temperature is typically less than 37°C, average brain temperature is 38.5°C, with deeper brain regions often exceeding 40°C, particularly in women during the daytime.
Previously, human brain temperature studies have relied upon data capture from brain-injured patients in intensive care, where direct brain monitoring is often needed. More recently, a brain scanning technique, called magnetic resonance spectroscopy (MRS), has enabled researchers to measure brain temperature non-invasively in healthy people. Until now, however, MRS had not been used to explore how brain temperature varies throughout the day, or to consider how an individual’s ‘body clock’ influences this.
The new study, led by researchers at the Medical Research Council (MRC) Laboratory for Molecular Biology, in Cambridge, UK, has produced the first 4D map of healthy human brain temperature. This map overturns several previous assumptions and shows the remarkable extent to which brain temperature varies by brain region, age, sex, and time of day. Importantly, these findings also challenge a widely held belief that human brain and body temperature are the same.
The research, published in the journal Brain, also included analysis of data from patients with traumatic brain injury, showing that the presence of daily brain temperature cycles strongly correlates with survival. These findings could be used to improve understanding, prognosis, and treatment of brain injury.
Striking brain temperature variation in health
To study the healthy brain, the researchers recruited 40 volunteers, aged 20-40 years, to be scanned in the morning, afternoon, and late evening over one day, at the Edinburgh Imaging Facility, Royal Infirmary of Edinburgh.
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