November 29, 2021

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PNAS: Why does memory worsen after staying up late?

PNAS: Why does memory worsen after staying up late?

PNAS: Why does memory worsen after staying up late?



 

PNAS: Why does memory worsen after staying up late?

 

In today’s society, staying up late has become the “ new normal ” for many young people . Do you also play with your cell phone bored in the early hours of a certain night, regretting that you shouldn’t have milk tea or supper just now, and feeling that it’s another day of insomnia? ? Or staying up late for the next day’s exam, PPT to report, etc.

 

We all know that staying up late is very harmful. In addition to making people feel sick the next day, it also damages the skin and liver, and even increases the risk of heart disease and cancer.

 

August 2021, researchers at the University of Michigan in the United States, ” the US Academy of Sciences ” (PNAS) published a report entitled: at Sleep Loss Drives acetylcholine- and Somatostatin gating of hippocampal interneuron-mediated INHIBIT Memory Consolidation Activity to research papers.

 

The study found that when staying up late leads to lack of sleep, the activity of inhibitory neurons in the hippocampus that navigate and process and store new memories in the brain increases .

These inhibitory neurons will limit the activity of neurons around them, making normal neuronal activity in the hippocampus unable to gather, thereby destroying memory consolidation.

 

PNAS: Why does memory worsen after staying up late?

 

Previous studies have shown that after a few hours of learning, there is a sensitive time window during which you must sleep to fully consolidate the memories generated by previous learning.

At this time, the neuronal activity in the hippocampus must remain undisturbed, and the neurons must remain undisturbed. The RNA transcription and protein translation must proceed normally.

 

First, the research team studied the interaction between sleep and wakefulness, hippocampal neuronal activity and activity-driven phosphorylation of ribosomal S6 protein, which is a component of ribosomes responsible for protein translation. This phosphorylation can affect which mRNAs are translated into proteins as neurons become more active. This regulation is important for adapting to the changing metabolic demands of neurons.

 

The research team gave the mice a fear stimulus. When the mice were allowed to sleep freely after being stimulated, they found that the phosphorylation of the ribosomal S6 protein in the dentate gyrus of the hippocampus increased, which is the first area where memories begin to form.

 

But when these mice were deprived of sleep, their phosphorylation levels throughout the hippocampus decreased. This disrupted the mice’s memories, which were originally formed in response to previous fear stimuli.

 

Next, the research team tried to investigate whether this activity-driven reduction in ribosomal S6 protein phosphorylation would have a similar effect on all neurons after lack of sleep.

The research team used bioinformatics to compare the mRNA abundance associated with phosphorylated S6 protein-containing ribosomes, and also examined the mRNA expression profile of previous sleep or non-sleep conditions.

 

The research team observed that after sleep deprivation, the abundance of one type of RNA transcripts, known to be exclusively present in interneurons that express the neuropeptide somatostatin and the inhibitory neurotransmitter GABA, increased significantly .

This indicates that greater activity between somatostatin-containing interneurons inhibits peripheral neurons, thereby inhibiting overall ribosomal S6 phosphorylation in the hippocampus, acting as a gate to slow down its firing.

 

Then, the research team conducted further studies on mice, and they found that when mimicking this inhibitory gating mechanism in free-sleeping mice, it can disrupt hippocampal activity and memory consolidation. On the contrary, inhibiting the activity of somatostatin-expressing interneurons after learning will increase the activity of neurons in the dentate gyrus, and is conducive to memory consolidation.

 

PNAS: Why does memory worsen after staying up late?

 

This research opens new doors for further research on how manipulating the relative balance between excitatory and inhibitory neuronal activity affects memory and sleep.

 

This study also reminds us that proper rest or sleep after studying for a period of time can better consolidate memory. Those who stay up late before the exam are obviously not a good idea. In fact, a good night’s sleep may be more helpful.

 

Paper link:

https://www.pnas.org/content/118/32/e2019318118

 

(source:internet, reference only)


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