Introduction
If you’re like me, you’ve probably made the joke
“I need to stick my head in the freezer”
Personally, I usually make this joke when I feel like I have a lot on my mind or am overwhelmingly busy. However, have you ever wondered what temperature your brain is truly at? Today, let’s take a deep dive into what brain temperature is, its importance, and issues that can arise with an abnormal brain temperature.
What is brain temperature?
The brain has a vital role in regulating body temperature. Particularly, a structure in the brain known as the hypothalamus is involved in temperature regulation (Shahid, 2024). But, the brain itself has been found to produce high amounts of heat. This especially happens due to neural activities, such as restoring equilibrium after action potentials occur and regulating the function of other neural and tissue cells (Kiyatkin, 2019). Additionally, the brain receives lots of blood flow from the heart; as much as “20% of total cardiac output” (Kiyatkin, 2019). This blood flow assists the brain by supplying crucial nutrients and oxygen required for healthy brain function and removes heat generated from neural activity (Kiyatkin, 2019).
Healthy men and women have an average brain temperature of 38.5°C (UK Research and Innovation, 2022). This temperature tends to vary as much as 4°C lower and 4°C higher (Kiyatkin, 2019). Brain temperature also tends to change depending on heat exchange between brain tissue and “between the brain and the rest of the body” (Kiyatkin, 2019).
Still, brain temperature generally varies from person to person, depending on many variables. Some of these variables include “time of day, brain region, sex, and age” (UK Research and Innovation, 2022). For example, deeper within the brain, temperatures often exceed 40°C. According to a study by Rzechorzek et al., temperature is typically highest in the afternoon and lower towards the evening (2022). Moreover, brain temperature also tends to be higher in women and increases with age (UK Research and Innovation, 2022). Activities that arouse blood flow to the brain have also been found to prolong higher-than-average brain temperatures (Kiyatkin, 2019). Additionally, certain brain regions, such as the hypothalamus, can also exhibit lower temperatures (Yulug et al., 2023).
Now, I’m sure you are wondering how researchers can determine one’s brain temperature. Few methods can be used to monitor brain temperature, as it is difficult to avoid using invasive techniques (Yulug et al., 2023). Noninvasive methods like “magnetic resonance imaging and spectroscopy, infrared spectroscopy, microwave radiometry, and ultrasound thermometry” have been used to monitor brain temperature (Yulug et al., 2023).
The Importance of Brain Temperature and its Implications
Brain temperature has many implications for our brain function. To begin, the blood-brain barrier - a crucial membrane between the blood and the brain (Dotiwala, 2024) - permeability is very temperature-dependent (Kiyatkin, 2019).
Brain cells are also sensitive to heat damage. Between 39-40°C, gradual heat damage can begin occurring in active brain cells, the blood-brain barrier, and vascular tissues (Bechtold and Brown, 2003; Sharma and Hoopes, 2003; Kiyatkin and Sharma, 2009). Active neural activity has been seen to stop at 42-43°C (Gahwiler et al., 1972). This can impact brain function, cause “structural damage to neural cells,” and even result in death (Kiyatkin, 2019)
Changes in brain temperature due to the activation of certain proteins in axon terminals can also influence the result of synapses, as neurotransmitter diffusion is temperature-dependent.
Although determined as only correlative, there seems to be a relation between brain temperature and survival. According to the UK Research and Institute's summary of Rzechorzek et al.'s study, which included traumatic brain injury patients, daily brain temperature fluctuations are strongly linked with survival.
More research is needed on brain temperature and its applications, but as more studies emerge, this growing field has promising results for determining the physiology and pathology of different diseases and ailments.
References
Bechtold, D. A., & Brown, I. R. (2003). Induction of Hsp27 and Hsp32 stress proteins and vimentin in glial cells of the rat hippocampus following hyperthermia. Neurochemical Research, 28(8), 1163–1173. https://doi.org/10.1023/a:1024268126310
Dotiwala AK, McCausland C, Samra NS. Anatomy, Head and Neck: Blood Brain Barrier. [Updated 2023 Apr 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519556/
Gahwiler, B. H., Mamoon, A. M., Schlapfer, W. T., & Tobias, C. A. (1972). Effects of temperature on spontaneous bioelectric activity of cultured nerve cells. Brain Research, 40(2), 527–533. https://doi.org/10.1016/0006-8993(72)90157-6
Kiyatkin E. A. (2019). Brain temperature and its role in physiology and pathophysiology: Lessons from 20 years of thermorecording. Temperature (Austin, Tex.), 6(4), 271–333. https://doi.org/10.1080/23328940.2019.1691896
Kiyatkin, E. A., & Sharma, H. S. (2009). Permeability of the blood-brain barrier depends on brain temperature. Neuroscience, 161(3), 926–939. https://doi.org/10.1016/j.neuroscience.2009.04.004
Nina M Rzechorzek, Michael J Thrippleton, Francesca M Chappell, Grant Mair, Ari Ercole, Manuel Cabeleira, The CENTER-TBI High Resolution ICU (HR ICU) Sub-Study Participants and Investigators, Jonathan Rhodes, Ian Marshall, John S O’Neill, A daily temperature rhythm in the human brain predicts survival after brain injury, Brain, Volume 145, Issue 6, June 2022, Pages 2031–2048, https://doi.org/10.1093/brain/awab466
Sharma, H. S., & Hoopes, P. J. (2003). Hyperthermia-induced pathophysiology of the central nervous system. International Journal of Hyperthermia: The Official Journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group, 19(3), 325–354. https://doi.org/10.1080/0265673021000054621
Shahid Z, Asuka E, Singh G. Physiology, Hypothalamus. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535380/
UK Research and Innovation. (2022, June 13). Healthy human brains are hotter than previously thought. Retrieved October 14, 2024, from https://www.ukri.org/news/healthy-human-brains-are-hotter-than-previously-though t/#:~:text=In%20healthy%20men%20and%20women,in%20women%20during%20t he%20daytime.
Yulug, B., Velioglu, H. A., Sayman, D., Cankaya, S., & Hanoglu, L. (2023). Brain temperature in healthy and diseased conditions: A review on the special implications of MRS for monitoring brain temperature. Biomedicine & Pharmacotherapy, 160, 114287. https://doi.org/10.1016/j.biopha.2023.114287
this is so interesting!!