Who never had woken up at night, rattled, with heart pounding due to a vivid memory of a scary dream?
We all had it. All those hazy imagery of the elaborate things you wouldn't think your mind's capable of creating. But where do they actually came from?
A new study led by György Buzsáki of New York University utilized rats in hopes of finally knowing such source of nightmares.
Rats have mental maps of the environment they're into thanks to their hippocampi or the two curved structures in the brain. Different places have their own distinct groups of neurons that processes the information. All of which activate together when, say, they have to "solve" a maze.
When their brain activity were later on measured, researchers found that such sequences actually reflects in their sleep. That is, they could be dreaming of the same routes they'd taken during wake time. Researchers believe this strengthens their memories that could eventually be stored in the long term storage.
To see if such memory replay also includes emotions, they puffed the rats' face with air from a keyboard cleaner at certain parts of the maze. That way, they're able to give them unpleasant but harmless experience.
Results showed that, indeed, rats learned to be afraid of such location. “They slow down before the location of the air puff, then run superfast away from it,” says Buzsáki’s colleague, Gabrielle Girardeau. “If you do it in the face of a human, they don’t like it either.”
They also found that such frightening experience had been replayed while the rats are sleeping. The fear centers in their brains re-activated at the moment they're into the same frightening spot. “This is the first [replay] study to bring in the emotional system,” says Dan Bendor of University College London. “That’s really important because our memories are not just information – we remember all the emotional context.”
However, whether they felt the same emotions or not during sleep is still unknown. “We can’t ask them,” Buzsáki’s says. But he does believe that if this reflects to humans' processes, this might be an explanation as to how certain nightmares develop. “It has been fairly well documented that trauma leads to bad dreams,” he says. “People are scared to go to sleep.”
But James Bisby of University College London begs to differ. “It seems to be more of a memory strengthening process. The memory would be more likely to be retrieved because it’s stabilised.”
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