The Hibernating Brain


Photo source: Laura Pontiggia/flickr


Several animal species choose to pass the harsh winter by entering a state called hibernation, or a period of inactivity. During this time, an organism undergoes profound reductions in metabolism, oxygen consumption, and heart rate. In some mammals, the core body temperature can drop to as low as 27º F. Due to these reductions, hibernation serves as a way to conserve energy during times of scarce resources, such as the winter months.

The arctic ground squirrel has emerged as a model species to study hibernation. Each year in September, they begin a seven-month period during which several dramatic biological changes occur. Research into the biological basis of hibernation has found that energy consumption switches from relying on carbohydrates to stored fats. Different environmental cues, such as light and temperatures, can trigger the enzymes that control metabolic activity, ensuring that energy-rich fats are utilized during hibernation.

Besides a simple reduction in metabolic activity, scientists have also discovered that while the squirrel hibernates, its brain undergoes several changes. In one study, researchers found that the squirrel’s neurons shrink. More recent research has also shown that hibernation induces modification of tau proteins, a process known to be associated with Alzheimer’s disease in humans. Interestingly, when squirrels rewarm, these modifications reverse. Given that the squirrels emerge from hibernation completely healthy, this may yield critical insights into how the brain repairs and renews itself.

Hibernation can vary across species but it serves a common purpose: to optimize survival during unforgiving conditions. While scientists continue to explore this behavior and the biology supporting it, the current data suggest that we may be able to use this information to better understand the brain and to uncover possible clinical applications for targeting neurodegenerative diseases like Alzheimer’s.



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