Finding The Hot Seat Of The Brain

Scientists in Japan have identified specific parts of the brain that are responsible for sensing changes in the temperature of the environment.

AsianScientist (Aug. 11, 2017) – Researchers at the Department of Integrative Physiology at Nagoya University Graduate School of Medicine in Japan have identified the brain regions involved in maintaining body temperature. Their findings are published in the journal Scientific Reports.

To maintain the body at an appropriate temperature despite changes in the environment—a process known as thermoregulation—there are a number of physiological and behavioral responses that can be adopted, such as shivering or moving into or out of direct sunlight. Although these responses are well understood, there is still a lack of understanding of the nerve and brain pathways that control them.

In this study, a team of scientists led by Professor Kazuhiro Nakamura at Nagoya University, Japan, built on earlier studies suggesting that two sensory pathways in the brain—the spinothalamocortical (STC) pathway and the lateral parabrachial nucleus-hypothalamus preoptic area (LPB-POA) pathway—affect thermoregulation. They injected toxic substances into parts of the brain involved in each of these pathways to disable them, and investigated how this influenced the ‘sensing’ of temperature changes and the responses to such changes.

“We tested the thermal responses of rats using an arrangement with two floor plates of different temperatures,” said Dr. Takaki Yahiro of Nagoya University. “Under control conditions, the rats preferred to stay on the 28°C plate rather than the 15°C or 38°C ones.”

“When we injected a toxin into part of the brain involved in the STC pathway, surprisingly, we found that the rats still showed this temperature preference, even though they had lost their ability to ‘feel’ temperature in the primary somatosensory cortex.”

However, when part of the LPB pathway was instead disabled by injecting another toxin, the rats no longer tried to avoid the hot and cold plates. Measuring their body temperature also revealed that their brains had warmed up to a hyperthermic state when they had been on a warm plate, showing that the body’s ability to regulate its core temperature had been damaged.

“These findings show the different functions of these two pathways in ‘sensing’ external temperature changes and in actually responding to these changes behaviorally,” said Nakamura. “We can now pursue a much better understanding of the circuits that control thermal comfort and how these help maintain the temperature of the body.”

The team hopes to build on this work by obtaining detailed findings on the specific groups of neurons involved in the pathways, also studying the involvement of emotion-related parts of the brain in thermoregulation and the behavior of seeking thermal comfort.

The article can be found at: Yahiro et al. (2017) The Lateral Parabrachial Nucleus, but Not the Thalamus, Mediates Thermosensory Pathways for Behavioral Thermoregulation.


Source: Nagoya University; Photo: Shutterstock.
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