This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: For most mammals, cold suppresses neural activity and diminishes the sense of touch. But the thirteen-lined ground squirrel can detect touch in conditions as low as 4°C (39°F), about as cold as the inside of a refrigerator, finds a new Yale study published in Current Biology.
For many mammals, including humans, prolonged exposure to cold can permanently damage nerves. But a team of Yale School of Medicine researchers found that ground squirrel mechanosensory neurons—the nerve cells that convert touch sensation into electrical signals—are adapted to survive at low temperatures and retain their signaling capabilities. "This was the first time we've demonstrated that any mammalian species can detect touch at this low a temperature," says Elena Gracheva, Ph.D., professor of neuroscience and cellular and molecular physiology and the study's co-principal investigator.
Gracheva and Slav Bagriantsev, Ph.D., professor of cellular and molecular physiology, have been investigating how sensory systems differ across species. In 2017, they discovered that thirteen-lined ground squirrels, as well as some other hibernating animals, don't perceive cold in the same way as other mammals. This is due to an adaptation in which the nerve cells that detect cold are less sensitive to low temperatures.
In the latest study, the researchers turned their attention from cold receptors to mechanoreceptors. These specialized nerve cells have long protrusions that penetrate the skin; if something comes in contact with those protrusions, they generate an electrical signal that informs the brain of physical contact. The team investigated whether mechanosensory neurons found in thirteen-lined ground squirrels had adaptations that enabled them to operate in the cold.
After incubating the neurons at 10°C, the scientists stimulated them and measured the electrical signals the cells produced in response. Exposure to this temperature would typically permanently damage or kill mechanosensory neurons from other mammals. But the researchers observed that the nerve cells from squirrels produced a robust response to stimulation.
Based on these findings, the researchers predicted that hibernating squirrels would respond to touch even at low body temperatures. To test this, they gently touched animals hibernating at 4°C (39°F) with a paintbrush. The stimulation was enough to awaken each one.
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