Memory may not work how we thought, study of mice in artificial hibernation finds

Recent research on mice in artificial hibernation suggests that long-term memories may not be maintained through individual, strong connections between neurons, as previously thought. Instead, the study found that memories are better preserved through a topological architecture within the brain's broader network. Co-author Kazumasa Tanaka, head of the Memory Research Unit at the Okinawa Institute of Science and Technology, stated that it is this network's structure, rather than individual, sturdy connections, that plays a more significant role in memory retention.

The findings, published in the journal Science, may challenge the traditional understanding of memory retention. Prior studies have shown that during hibernation, animals' brains shrink and lose cell-to-cell connections. However, these animals still retain their pre-hibernation memories, such as recognizing conspecifics or remembering food locations.

To investigate this phenomenon, the researchers focused on the hippocampus, a crucial memory processing center in the brain, and studied episodic memories related to specific events and experiences. In their experiments, mice learned to associate a specific setting with a mild shock or locate sugar pellets within a maze. Upon placing these mice in artificial hibernation, their brains rapidly underwent significant changes, losing more than half of their synapses within 24 hours.

Despite this dramatic synaptic loss, the mice retained their learned behaviors upon waking from hibernation. The study compared these hibernating mice to others subjected to long-term anesthesia and a molecule blocking synapse strengthening. While both groups experienced synapse loss, only the hibernating mice retained their memories.

The researchers discovered that certain synapse clusters within the hibernating mice appeared to be resilient during the culling process, which may explain how memories are preserved even when many connections disappear.