Rules Of Memory 'beautifully' Rewritten
Rules of memory 'perfectly' rewritten
What really happens when we make and store memories has been unravelled in a discovery that surprised even the scientists who made it.
The US and Japanese team found that the brain "doubles up" by simultaneously making two memories of events.
One is for the here-and-now and the other for a lifetime, they found.
It had been plotting that all memories start as a small-term memory and are then slowly converted into a long-term one.
Experts said the findings were surprising, but also fantastic and convincing.
Two parts of the brain are heavily involved in remembering our personal experiences.
The hippocampus is the place for small-term memories even as the cortex is home to long-term memories.
This thought became well-known after the case of Henry Molaison in the 1950s.
His hippocampus was hurt all through epilepsy surgery and he was no longer able to make new memories, but his ones from before the surgical course of action were still there.
So the prevailing thought was that memories are formed in the hippocampus and then went to the cortex where they are "banked".
The team at the Riken-MIT Center for Neural Circuit Genetics have done something mind-bogglingly advanced to show this is not the case.
The experiments had to be performed on mice, but are plotting to apply to human brains too.
They involved watching specific memories form as a cluster of connected brain cells in reaction to a shock.
Researchers then used light beamed into the brain to control the endeavor of individual neurons – they may possibly literally switch memories on or off.
The consequences, published in the journal Science, showed that memories were formed simultaneously in the hippocampus and the cortex.
Prof Susumu Tonegawa, the director of the research centre, said: "This was surprising."
He told the BBC News website: "This is contrary to the well loved hypothesis that has been held for decades.
"This is a significant advance compared to previous knowledge, it's a huge shift."
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 small-term memory in the hippocampus.
Though, they may possibly then make the mice remember by manually switching the long-term memory on (so it was certainly there).
"It is immature or silent for the first several days after formation," Prof Tonegawa said.
The researchers also showed the long-term memory by no means 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.
Dr Amy Milton, who researches memory at Cambridge University, described the study as "fantastic, elegant and extremely impressive".
She told the BBC News website: "I'm quite surprised.
"The thought you need the cortex for memories I'm comfortable with, but the fact it's so early is a surprise.
"This is [just] one study, but I reflect they've got a strong case, I reflect it's convincing and I reflect this will tell us about how memories are stored in humans as well."
For now, this is simply a cut of fundamental science that clarifies how our bodies work.
But Prof Tonegawa says it may illuminate what goes on in some diseases of memory counting dementia.
One of his previous studies showed mice with Alzheimer's were still forming memories but were not able to retrieve them.
"Understanding how this happens may be significant in brain disease patients," he said.
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