Our leading hypothesis(假设；假说) for how our memories are stored is that when you learn something, the connections among neurons(神经元) involved get stronger and physically larger, and that constitutes(构成；组成) the memory. The trouble is that these connections significantly change over time—they’re plastic(可塑的；可变的). “If you compare the arrangement(排列；布局) of these connections on day one with the same on day four or five, it's very, very different," says Kazumasa Tanaka, a neuroscientist(神经科学家) at the Okinawa Institute of Science and Technology Graduate University in Japan. To learn how a memory that can last for years can sit on(依赖于；建立在) hardware that shifts(转移；变动) every few days, Tanaka’s team made the shift a bit more dramatic(剧烈的；显著的). In a recent Science study, they induced(诱导；引起) a hibernation-like state(类冬眠状态) in mice, which basically erased(擦除；抹去) the state of more than half of their synapses(突触). And yet the mice apparently(显然地；表面上) have kept their memories.
Hibernation on demand(按需冬眠；可控冬眠)
Hibernation(冬眠) is a specialty(特长；专长) of squirrels(松鼠), hamsters(仓鼠), and bears(熊), but the neural circuit(神经回路) that triggers(触发) it is conserved(保守的；保留的) across mammals(哺乳动物), and is present in species(物种) that never hibernate in the wild(在野外)—like mice. In June 2020, a team of researchers led by Takeshi Sakurai, a neuroscientist at the University of Tsukuba and a collaborator(合作者) on Tanaka’s study, developed a technique to artificially(人工地) activate(激活) this hibernation circuit. This can be done by activating a population(群体；种群) called Q neurons in a region of the hypothalamus(下丘脑).