Cold Memories Trigger Whole-Body Metabolic Changes in Mice

This groundbreaking study reveals how the brain stores temperature experiences as memories that can trigger immediate physiological responses to maintain thermal homeostasis. The research addresses a fundamental question about brain-body interactions and whether memories can directly influence metabolic function.

Researchers trained mice using thermoregulatory Pavlovian conditioning, exposing them to 4°C temperatures in specific contexts while maintaining normal 21°C temperatures in control environments. They combined this behavioral training with advanced neuroscience techniques including engram-labeling technology, optogenetics, and chemogenetics to identify the neural circuits involved.

The key finding was that mice returned to cold-associated environments showed increased oxygen consumption, energy expenditure, and thermogenic gene expression in brown adipose tissue, even when the actual temperature was normal. This response persisted for several hours and was accompanied by increased movement and core body temperature. The effect was specific to cold-paired contexts and not simply due to environmental novelty.

The researchers identified cold-sensitive memory engrams in the hippocampus and hypothalamus that form functional networks during memory retrieval. Artificial reactivation of these neural ensembles could reproduce the physiological responses seen during actual cold exposure, while disrupting these circuits prevented cold memory retrieval.

These findings demonstrate that memory systems can directly control whole-body autonomic and behavioral responses, enabling animals to anticipate thermal challenges based on previous experience. This represents a novel mechanism by which the brain prepares the body for environmental challenges through learned associations, potentially offering insights into adaptive metabolic responses and thermoregulation disorders.