How does the brain differentiate hot and cold?

By Viola Spada

Edited by Olivia Ural

Researchers at Waseda University (Tokyo, Japan) studied brain activity when exposed to hot or cold temperatures using a technique called electroencephalography (EEG), which records the electrical activity in the brain by placing small sensors on the scalp. These sensors detect and measure the electrical signals within the brain, which change when different parts of the brain are active. The scientists discovered that processing of both hot and cold sensations activates the same ten areas of the brain, but in different ways. Remarkably, these changing activities affect how we behave. We now have a better understanding of how the brain encodes temperature information because of this research.

The cortex, the outermost layer of the brain, is crucial for temperature detection. It's unclear, though, how it can tell the difference between hot and cold. Thermal comfort is frequently a personal experience; what one person finds comfortable may be too hot or too cold for another. 

Professor Kei Nagashima and Dr. Hironori Watanabe of Waseda University, together with others, employed EEG to monitor brain activity in reaction to temperature changes in order to better understand this phenomenon. A study was conducted where twenty individuals were given either hot (40°C) or cold (24°C) exposures to their right index and middle fingers for 15 seconds. In between these temperature exposures, the temperature was maintained at 32°C for 10 second intervals. A wearable EEG device was used to record brain activity.

The findings showed that while the same 10 brain areas were active in response to hot and cold temperatures, the patterns of activity varied. This variation in brain activity causes distinct reactions and behaviours, helping the brain determine whether a temperature is hot or cold. The right hemisphere of the brain showed the highest concentration of activity. As a result of this work, more impartial methods of evaluating thermal comfort may be developed. Current approaches, which frequently rely on firsthand accounts, can be imprecise, according to Professor Nagashima. With a better grasp on how the brain responds to temperature, we may be able to assess and control interior environments more effectively and lower the health hazards associated with subjective temperature assessments.

Works cited

Waseda University. "Hot or cold? How the brain deciphers thermal sensations." ScienceDaily. ScienceDaily, 22 January 2025. www.sciencedaily.com/releases/2025/01/250122130031.htm.