Research Hit: Sleep Deprivation Impairs Memory Formation
New research shows impaired replay after sleep deprivation blocking memory formation
We know sleep helps to form memories, isn’t this old news?
Yes, I have reported multiple times on sleep and particularly how it helps with memories. For example:
I also reported on how the brain seems to play through future scenarios during sleep here:
However, a lot of the research is not neuroscience research, and this particular research I am reporting on identified some of the precise mechanisms of what happens in the brain during sleep and memory formation and how precisely sleep deprivation can block and impair this process.
Ok, and what is happening then? Isn’t our brain rewiring?
Rewiring is one process but this normally refers to building stronger connections between adjacent neurons and not building new connections across the brain (which basically doesn’t happen in us adults).
Two new studies from the University of Michigan explored the process of sleep in rats brains and specifically in activation of neurons in the Hippocampus, a region deep in the brain (that is named after a seahorse, by the way), that is a key and critical hub for memory formation and processing.
Rewiring, per se, is not what they found.
What did they find then?
They found evidence that reactivation of neurons during sleep is what helps form and stabilise new memories.
How?
This was through being able to image brain of rats and specific neurons precisely in a maze. Rats in a maze might sound like an old cliché and a weird thing to do but is incredibly useful. As rats navigate a new maze, specific neurons in the hippcaompus and neighbouring regions activate to each location, these are known as “place neurons”.
With new technologies we can now see this activation as they are navigating and also whether these are reactivated during sleep But not only single neurons, also activation patterns across neurons and the subsequent brain waves associated with this.
And did these reactivate during sleep?
Yes, these neurons associated with memories did reactivate during sleep and they could also see whether these memories drifted or not and then subsequently how this affected memories when going through the maze again.
So, sleep allow neurons to replay and this activity strengthens memories?
Precisely. But then the next question was how does sleep deprivation impact this reactivation and subsequent memory. We know from plenty of other studies that sleep impairs memory but this shows the precise reasons.
And…?
For that we have to go back to something called sharp-wave ripples that I also reported on previously:
These are basically strongly coordinated patterns, and waves of activity, that come from the hippocampus. They discovered that the sharp-wave ripples were similar in sleep and sleep deprivation which might seem disappointing until we look closer.
These waves sharp-wave ripples were of lower amplitude and lower power - basically a lot weaker during sleep deprivation. What’s more the reactivation of the maze experience during these sharp-wave ripples was absent in about half of the cases.
So, the experiences seem to be lower during sleep and sleep deprivation stops replay for about half the population!
Exactly.
But does catching up on sleep help recover his?
Well, you can’t recover some thing that hasn’t been remembered in the first place. But they did research precisely this - what happens after regaining their sleep deprivation - catching up on sleep?
Sharp-wave ripples rebounded but not back to normal but impaired replay was not recovered.
So, in summary sleep deprivation blocks memory formation!
Yes, it’s that simple.
So, get a good night’s sleep regularly, especially after studying or an important day at work.
References
Kourosh Maboudi, Bapun Giri, Hiroyuki Miyawaki, Caleb Kemere, Kamran Diba.
Retuning of hippocampal representations during sleep.
Nature, 2024; 629 (8012): 630
DOI: 10.1038/s41586-024-07397-x
Bapun Giri, Nathaniel Kinsky, Utku Kaya, Kourosh Maboudi, Ted Abel, Kamran Diba.
Sleep loss diminishes hippocampal reactivation and replay.
Nature, 2024
DOI: 10.1038/s41586-024-07538-2