Sleep deprivation would increase the activity of inhibitory neurons in the hippocampus, an area of the brain essential for navigation, as well as for processing and storing new memories.
- There is a sensitive window of time, a few hours after learning, during which sleep allows a memory to be fully consolidated.
- Activity in the dentate gyrus, the first region where memories begin to form, located in the hippocampus, is disrupted by lack of sleep.
Before an exam, students sometimes sleep all night to revise and hope to be as prepared as possible. This would be counterproductive and a good night’s sleep might be more helpful to them. Depriving yourself of a night’s sleep would increase the activity of inhibitory neurons in the hippocampus, an area of the brain essential for navigation, as well as for processing and storing new memories. This is the conclusion of a study which has just been published in the PNAS.
A sensitive time window after learning
This study highlights the importance of sleep to better mobilize one’s memory. Previous studies have shown that there is a sensitive window of time, a few hours after learning, during which sleep allows a memory to be fully consolidated. During this period, neuronal activity should remain intact in the hippocampus, and transcription and translation of RNA in neurons should occur normally.
Researchers studied the interplay between sleep and wakefulness, the activity of hippocampal neurons, and the activity-induced phosphorylation of S6, a component of ribosomes, tiny organelles that translate mRNA into protein . This phosphorylation event affects mRNAs which are translated into proteins as neurons become more active. This regulation may be important in adapting to the ever-changing metabolic demands of neurons.
Disturbed hippocampal activity
For the study, the researchers gave the mice a fear stimulus. When the mice were allowed to sleep freely after the stimulus, he found that S6 phosphorylation increased in a part of the hippocampus called the dentate gyrus, the first region where memories begin to form. But when the mice were deprived of sleep, they observed that phosphorylation decreased throughout the hippocampus. This disrupted the mice’s memories that would otherwise have been formed in response to the fear stimulus.
“In disorders such as Alzheimer’s disease, where sleep disturbances are common, there may be a relationship between the physiological mechanism described in this study and memory loss.says Sara Aton, co-lead author of the study. But there could be a protective function of neurons, or an adaptive psychological reaction against stressful memories..”
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