How Memories Persist Even After Synapse Loss
- Researchers at the Okinawa Institute of Science and Technology Graduate University and the University of Tsukuba published a study in Science demonstrating that mice can retain long-term memories...
- Neuroscientists have long held that learning physically alters the brain by strengthening and enlarging connections among involved neurons.
- While hibernation is a biological specialty observed in wild animals like squirrels, hamsters, and bears, the underlying neural circuit remains conserved across broader mammalian species, including those that...
Researchers at the Okinawa Institute of Science and Technology Graduate University and the University of Tsukuba published a study in Science demonstrating that mice can retain long-term memories despite an artificial hibernation state erasing more than half of their synaptic connections.
Challenging Long-Standing Models of Synaptic Plasticity
Neuroscientists have long held that learning physically alters the brain by strengthening and enlarging connections among involved neurons. This network of connections constitutes the physical substrate of memory. However, these synaptic arrangements exhibit high volatility under normal biological conditions, shifting significantly across intervals of just a few days.
As Kazumasa Tanaka—a neuroscientist at the Okinawa Institute of Science and Technology Graduate University in Japan—points out, contrasting the layout of these connections between day one and days four or five reveals that “it’s very, very different.” To investigate how stable memories persist atop such shifting hardware, Tanaka and his research team subjected test subjects to a dramatic physiological shift.
Inducing Hibernation on Demand in Laboratory Mice
While hibernation is a biological specialty observed in wild animals like squirrels, hamsters, and bears, the underlying neural circuit remains conserved across broader mammalian species, including those that do not hibernate naturally. An experimental procedure to artificially turn on this inactive hibernation pathway was created in June 2020 by a team of scientists headed by Takeshi Sakurai, who is a neuroscientist at the University of Tsukuba and also worked with Tanaka on his study.
The method involves targeting and activating a specific population of cells known as Q neurons located within the hypothalamus region of the brain. By triggering this neural population, the researchers successfully induced a hibernation-like state in laboratory mice for the recent study published in Science. This induced state wiped out the structural state of more than half of the animals’ synapses, yet subsequent observation revealed that the mice retained their prior memories.
