New research published in Nature Neuroscience looks at how rats’ sleep is affected by an unpleasant experience. This research is helping us understand the link between dreaming and our emotions. Science columnist Torah Kachur explains.
Do rats dream?
No, not in the way we can say that they have a subjective experience during their sleep. They can’t exactly wake up and tell us about their dream of falling into the abyss or their teeth falling out — two very common human dreams.
But, they do share brain structures with humans that are active during sleep in both species — the amygdala and hippocampus. The amygdala is involved in processing emotions and the hippocampus is involved in memory consolidation, especially a type of memory called episodic memory, where you remember all the details of one event. Rats have those structures in the brain. We don’t know if they are working the same way, but we now know that they are both active during sleep, similar, we think, to the way humans dream.
How was this discovered?
Researchers from New York University in the Neuroscience department studied trained rats by looking at their brain waves during sleep before and after a training session. Gabrielle Girardeau is the post-doctoral researcher who was the lead author on this new study.
“The rats are training to run back and forth on a linear track,” says Girardeau.
“They’re getting water rewards… at both ends of the track. And when we start the experiment what we do is we introduce an aversive stimulus. It’s not painful, it’s just unpleasant… it is an air puff. And they learn to fear these precise locations because of the air puff… After we train them on that, we record a bunch of sleep.”
That sleep the researchers recorded revealed that the amygdala and hippocampus were firing together in a more coordinated fashion than if the rats didn’t experience the air puff.
Why is the fact that the amygdala and hippocampus were firing together important?
This is because it indicates that the rats are processing emotional information, this negative experience, in a way that mimics how humans consolidate memories — using the…