So say Stanford University neurologists, who have actually seen memories under a microscope – and watched them vanish:
Now Mark Schnitzer, an associate professor of biology and of applied physics, has leveraged microscopy tools developed in his lab and for the first time was able to monitor the connections, called synapses, between hippocampal neurons and confirm what neuroscientists thought might be happening. In the mice he and his team studied, the connections between neurons lasted about 30 days, roughly the duration over which episodic memories are believed to stay in the mouse hippocampus. The work was published on June 22 in Nature.
…
When mice experience a new episode or learn a new task that requires spatial navigation, the memory is stored for about a month in a structure at the center of the brain called the hippocampus (it is stored slightly longer in people). If mice have hippocampus-disrupting surgery within a month of forming a memory – a memory of meeting a new cage-mate or navigating a maze – that memory is lost.
If the disruption occurs after more than a month, then the mouse still retains the memory of a new friend or location of food. That’s because the memory had been relocated to a different region of the brain, the neocortex, and is no longer susceptible to disruption in the hippocampus.
“The thought is that memories are gradually moved around the brain,” said Schnitzer, who is also a member of Stanford Bio-X and the Stanford Neurosciences Institute.