Remember when you've pulled an all-nighter to study and prepare for tomorrow's test but when you finally get to take it, all of a sudden you just can't seem to remember the answers?
Well, scientists from the University of Michigan may have a possible explanation why. They have discovered that your brain rhythms or your sleep-associated oscillations in your hippocampus are being interrupted when you lack sleep causing your forgetfulness
Utilizing mice, they recorded the baseline hippocampal activity when they're placed them into a new environment to explore, gave them a mild foot shock, then put them back to their cages to sleep properly. “If you return the mouse to that same structure a day or even a couple months later, they will have this very stereotyped fear response, which is that they freeze,” says Sara Aton, senior author of the study
. “But if you sleep-deprive an animal for a few hours after that context-shock pairing, the mouse won’t remember it the next day.”
This shows that the mices' CA1, the sleep-associated oscillations in the hippocampus, were more robust after learning. So the researchers took a new group of mice, did the same normal sleeping routine, but also gave them a drug to inhibit a small population of parvalbumin-expressing neurons in CA1. Results showed that it seemed to erase normal learning, making the mice forget that there was actually a shock to their routines.
“The dominant oscillatory activity, which is so critical for learning, is controlled by a very small number of the total cell population in the hippocampus. This changes the narrative of what we understand about how networks work. The oscillations that parvalbumin cells control are linked to global network changes, or stability," says graduate student and co-author of the study Nicolette Ognjanovski. "Memories aren’t stored in single cells, but distributed through the network.”
The researchers also compared the neural connections of the two groups of mice. It turns out that the group that have no CA1 blocked had stronger neural connections than the group that have had their sleep-associated oscillations blocked. “It seems like this population of neurons that is generating rhythms in the brain during sleep is providing some informational content for reinforcing memories,” Aton says. “The rhythm itself seems to be the most critical part, and possibly why you need to have sleep in order to form these memories.”
Hence, developing a better sleep cycle
might actually prevent you from forgetting your keys inside the house over and over again. Never too late for a good night's sleep
! Sweet dreams!