Cold Enough to Start Shivering?

The brain wiring that tells your body when to start shivering is different from the pathways that let you consciously decide when you're cold, according to new research from the Oregon Health and Science University (OHSU).

By studying lab rats, researchers Kazuhiro Nakamura and Shaun Morrison were able to follow the sensory path leading from the skin to specialized cells in the brain. Those cells, located in the lateral parabrachial nucleus, send information to another portion of the brain -- the preoptic area -- that decides whether it's time for the body to start shivering.

"One fascinating aspect of this study is that it shows the sensory pathway for shivering, which can be thought of as brain wiring, is parallel to but not the same as the sensory pathway for conscious cold detection," said Nakamura, an OHSU Fellow for Research Abroad from the Japan Society for the Promotion of Science. "In other words, your body is both consciously and subconsciously detecting the cold at the same time using two different but related sensory systems."

Shivering is an automatic response set off by the brain as a way to help keep the body warm when it's very cold outside. The subconscious response is one of many automatic -- or homeostatic -- functions controlled by the brain. Other such functions, which are essential to our survival but not under our conscious control, include regulation of breathing rates, blood pressure and heart rates.

"Shivering, which is actually heat production in skeletal muscles, requires quite a bit of energy and is usually the last strategy the body uses to maintain its internal temperature to survive in a severe cold environment," Nakamura said. "Other strategies to defend against the cold, such as reducing heat loss to the environment by restricting blood flow to the skin, also appear to be controlled by the sensory mechanism that we found."