The brain may forget in order to save energy, a new study suggests.
So, our brains contain mechanisms that help us erase unnecessary learning.
Now scientists have uncovered how this may happen at the cellular level.
The results come from a strange finding about how we learn.
You may know the story of Pavlov’s dogs, who were taught to salivate at the ringing of a bell because they associated it with being fed.
Similarly, both humans and animals can learn to link a certain tone with a puff of air to the eyes.
This, of course, causes people to blink — it’s an automatic response.
However, you can remove the actual puff of air to the eyes and people will blink at just the sound of the tone.
They have learned to link the tone to the puff of air so they blink — even when there’s no puff.
Here’s the kink in the story, though.
When you add the puff of air back in, paradoxically people’s learning gets worse.
It’s like the extra stimulus is actually causing forgetting.
Professor Germund Hesslow, who led the new research said:
“Two stimuli therfore achieve worse results than just one.
It seems contrary to common sense, but we believe that the reason for it is that the brain wants to save energy.”
What seems to be happening is that when we’ve successfully learned a link, a neuronal braking mechanism activates.
Professor Hesslow continued:
“You could say that the part of the brain that learned the association (a part of the brain called the cerebellum) is telling its ‘teacher’: ‘I know this now, please be quiet’.
When the brain has learnt two associations, the brake becomes much more powerful.
That is why it results in forgetting, usually only temporarily, however.”
The new research describes how the nerve cells learn and forget.
Professor Hesslow said:
“Obviously, it should be important for teachers to know the mechanisms by which the brain erases the things it considers unnecessary.
You do not want to accidentally activate these mechanisms.”
The study was published in the journal PNAS (Rasmussen et al., 2015).
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