Hibernation in mice causes significant loss of synapses
Researchers at the Okinawa Institute of Science and Technology observed that a hibernation-like state in mice erases over half of their synapses. Despite this, the mice appear to retain their memories.
Scientists at the Okinawa Institute of Science and Technology (OIST) in Japan have discovered a significant loss of synapses, the connections between neurons, in mice induced into a hibernation-like state. The study, published in Science, challenges existing theories on how memories are stored and maintained.
The prevailing hypothesis for memory storage suggests that connections between neurons strengthen and physically grow when learning occurs. However, these connections are plastic and change continually. Kazumasa Tanaka, a neuroscientist at OIST, notes that the arrangement of these connections can differ drastically even within a few days.
Tanaka's research team aimed to understand how memories lasting for years could reside in neural hardware that shifts so frequently. They induced a hibernation-like state in mice, resulting in the erasure of over half of their synapses' structure. Paradoxically, the mice seemed to have retained their memories despite this extensive synaptic loss.
The research utilized a technique developed by Takeshi Sakurai, a neuroscientist at the University of Tsukuba and a collaborator on the study. This method artificially activates a population of Q neurons in the hypothalamus, triggering the hibernation state. This neural circuit is conserved across mammals, even in species that do not naturally hibernate.
These findings raise new questions about memory persistence in the absence of previously assumed physical synaptic structures and offer novel insights into the neurobiology of memory.