During sleep, some resting brain neurons not only replay, but even rehearse. This discovery is an insight proposed by a team from Rice University and the University of Michigan in a study on sleep and learning. According to recent reports from the journal Nature and the official website of Rice University in the United States, scientists are studying individual neurons in the brain from an unprecedented perspective. Almost everyone who has experience preparing for exams knows that "reviewing before bedtime is twice the result with half the effort". This is because sleep helps to turn new experiences into stable memories. Years ago, research found that if animals explore new environments before resting, the neurons in their brains will discharge in a way that replicates the trajectory of the animal's exploration process. The spatial representation of many special neurons in the hippocampus is also stable during sleep. But is the brain's ability during rest limited to this? Scientists have tracked "spiky ripples," a neuronal activation pattern that plays a role in consolidating new memories by marking which parts of new experiences will be stored as memories. Fortunately, scientists have observed for the first time how these individual neurons maintain stable spatial representations during rest periods. They demonstrated what they called a 'drill' by measuring memory test performance after a nap (not after a period of wakefulness or lack of sleep). Scientists first trained mice to run back and forth on a track, with "rewards" at both ends of the track. They observed how individual neurons in the animal hippocampus' discharge 'during this process. By calculating the average discharge rate of multiple rounds back and forth, it is possible to estimate the position field of a neuron or the environmental area that a specific neuron is most concerned about. Scientists have used a statistical machine learning method that can use neurons to draw estimates of the location of animal dreams. Next, using these dream locations, estimate the spatial tuning process of each neuron in the dataset. It may sound complicated, but this method can confirm that for most neurons, the spatial representations formed during the experience of a new environment remain stable for several hours after the experience. Surprisingly, what these neurons do during sleep is not just stabilizing experiential memory - when scientists put the animal back into the environment for the second time, the changes in neurons do reflect what the animal learned during sleep, even as if the second contact space actually occurred while the animal was sleeping, and the real 'second time' turned into a 'replay'. In the past, almost all plasticity studies (mechanisms that allow neurons to reconnect and form new representations) focused on what happens during animal wakefulness and when stimuli appear. Now, what people observe is the miraculous changes during sleep when there are no relevant stimuli. This observation constitutes direct evidence of neural plasticity that occurs during sleep. (New Society)