All memories start as a short-term memory and then slowly convert into a long-term memory — or so we thought:
Two parts of the brain are heavily involved in remembering our personal experiences.
The hippocampus is the place for short-term memories while the cortex is home to long-term memories.
This idea became famous after the case of Henry Molaison in the 1950s.
His hippocampus was damaged during epilepsy surgery and he was no longer able to make new memories, but his ones from before the operation were still there.
So the prevailing idea was that memories are formed in the hippocampus and then moved to the cortex where they are “banked”.
The results, published in the journal Science, showed that memories were formed simultaneously in the hippocampus and the cortex.
The mice do not seem to use the cortex’s long-term memory in the first few days after it is formed.
They forgot the shock event when scientists turned off the short-term memory in the hippocampus.
However, they could then make the mice remember by manually switching the long-term memory on (so it was definitely there).
“It is immature or silent for the first several days after formation,” Prof Tonegawa said.
The researchers also showed the long-term memory never matured if the connection between the hippocampus and the cortex was blocked.
So there is still a link between the two parts of the brain, with the balance of power shifting from the hippocampus to the cortex over time.