A new study has found that normal human brain temperatures fluctuate much more than we thought, and this may be a sign of healthy brain function. In healthy men and women, where the oral temperature usually does not exceed 37°C, the average brain temperature is 38.5°C, while in deeper areas of the brain it often exceeds 40°C, especially in women during the daytime.
Previous studies of human brain temperature have relied on data from traumatic brain injury patients in intensive care, where direct brain monitoring is often required. More recently, a brain-scanning technique called magnetic resonance spectroscopy (MRS) has allowed researchers to measure brain temperatures noninvasively in healthy people. So far, however, MRS has not been used to study how brain temperature changes during the day, or to consider how this is affected by a person’s body clock.
A new study led by scientists at the Medical Research Council’s (MRC) Molecular Biology Laboratory in Cambridge, UK, has created the first four-dimensional map of healthy brain temperature. This map overturns several previous assumptions and reveals the astonishing extent to which brain temperature varies across brain regions, age, gender, and time of day. Importantly, these results also refute the widely held belief that the temperature of the human brain and body is the same.
The study, published in the journal Brain, also included an analysis of data from patients with traumatic brain injuries, showing that the presence of diurnal brain temperature cycles was strongly correlated with survival. These results can be used to improve the understanding, prognosis, and treatment of traumatic brain injury.
Human brain temperature was measured in healthy adults at three time points during the day (9am, 4pm and 11pm). This video uses research data to simulate the change in brain temperature in men and women after ovulation at an interval of one hour (two days of data are simulated).
To study healthy brains, the researchers recruited 40 volunteers aged 20-40 who were scanned in the morning, afternoon and late evening over the course of one day at the Edinburgh Imaging Center of the Edinburgh Royal Infirmary.