Why sleep improves memory Bashny.Net

To short-term memory became long-term, in the brain to form new neuronal contacts, and the formation of such contacts happens best during sleep the activity of the nerve cells.

Turning short term memory into long term is called consolidation of memory, and neuroscientists are trying hard to figure out how and why this happens. Quite some time found out that memory consolidation is very good during sleep. That is, to memorize before the exam read the textbook, need to sleep, then the information, that is, settles in the head, that is, go into long-term storage. Evidence of a link between sleep and memory quite a lot. For example, researchers from the University of California in riverside found that sleep drugs not only normalize sleep, but also improve memory. And their colleagues from the University of California at Los Angeles was able to describe information processes in the brain that are associated with memory consolidation during sleep.





The fact that this important process occurs during sleep, is not surprising because for a long time already all know that sleep is just another form of brain activity. It is believed that specific neural impulses, "sleepy" brain waves associated with the fact that our nervous system is responsible for sorting the received information until the external signals do not interfere. But what are neurons, what cellular and molecular mechanisms involved here, biologists for a long time to figure out worked.

To find out what happens to neurons during memory consolidation, Wen-Biao Gan (Wen-Biao Gan), and the staff of new York University has created a genetically modified mouse whose neurons of the motor cortex were synthesized green fluorescent protein. With its help it was possible to observe changes in the nerve cells, for example, where and when are formed dendritic spines, special outgrowths on the dendritic processes of nerve cells. The appearance of the spine suggests that the neuron is ready to create contact with another neuron, in other words, the spine precedes the synapse. Thanks to the synapses are formed the neural pathways required for memorizing information. When we, for example, learning to ride a bike, we have in the brain develop new neural circuits that have emerged in response to the need for a new way to coordinate muscular efforts. Then, when we sit on the bike, these neural circuits are re-enabled unless they for some reason have not broken up, if the synapses between neurons have not disappeared. Returning to dendritic spines, we can say that they are evidence of the response of the neuron to new information and readiness to remember.

In fact, the mice in the experiment also set a something like a bike: animals had to maintain balance on the revolving stick that was rotated faster and faster. Over time, the mouse remembered what to do, and not fall with her. While the neurons of the motor cortex there is the very dendritic outgrowths of the cells understood that the new incentive are important for the body and was preparing to form a new chain. Then the researchers changed the conditions of the experiment: mice were trained on a turning stick one hour, but then some animals were sent to bed at seven o'clock, and the other had the same time to stay awake. It turned out that those mice who were allowed to sleep, dendritic spines were growing more active. In other words, the sleep helped nerve cells tune in to the memorizing of new information.

Moreover, the nature of the appearance of dendritic spines were dependent on what exercise had to do. For example, if the mouse had to go on rotating the stick in one direction, the spines appeared on the same dendrites, but if I had to go to the other side, the spines appeared on other dendrites. That is, the cellular morphology of neural processes depend on that information need to be processed.





Finally, neuroscientists were able to show that the cells of the motor cortex, from which depended the exercise, are active during slow-wave sleep phase. This activation during sleep was critical to the formation of the infamous spines: if the "sleepy" activity of the cells is suppressed, then the spines were not formed. It is as if the brain is again replayed for himself what he was supposed to perform while awake is replayed to better remember.

The result was such a scheme: neurons during wakefulness get some incentive or perform some procedure, and then during sleep, these cells are reactivated, and that reactivation stimulates cellular restructuring, promoting long-term retention incentive. The fact that all this is happening, neuroscientists have assumed for a long time, but now managed to get experimental confirmation, and not any Drosophila, and the mammalian brain. Although, of course, now scientists need to figure out what molecular processes are involved, what genes and proteins control the increase in dendritic spines during sleep which signaling pathways work here, etc.

Speaking of fruit flies: a few years ago, researchers from Washington University in St. Louis and the University of Wisconsin in Madison staged similar experiments with fruit flies, and then the results told the same thing – that sleep is necessary for memory consolidation. However, neuroscientists have observed clearing of the brain of Drosophila from the synapses, that is, there is something like edition of nerve circuits, purification of neurons from unnecessary connections that would have taken resources away from necessary contacts. Most likely, this elimination of unnecessary synapses is not a specific process peculiar to mere insects (or arthropods, or invertebrates), and in the brain of higher animals at the time of "sleepy" consolidation of memory along with the formation of new synapses occurs and the severance of old – you only have to see it in the experiment.



Source: nkj.ru