Scientists at the University of California at Lon Angeles and the University of Tel Aviv (Israel) improved the memory of sleeping people by synchronously stimulating certain regions of their brain. This is proof of the dominant theory about how brain rhythms influence the formation of memories. The results of the study are reported in an article published in the journal Nature Neuroscience.

Sleep is known to play an important role in the transition of memories from short-term to long-term, a process known as memory consolidation. The initial phase of the formation of declarative memories, that is, available for conscious recall (facts and events), depends on the hippocampus, but over time, this function falls on the neocortex. Embedding new information in the neocortex occurs due to the reactivation of memories by the hippocampus during deep sleep, while “ripples” occur in this area of the brain - short neural pulsations with a frequency of 80-120 Hertz.

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The experiment involved 18 people aged 19-47 suffering from severe epilepsy resistant to drug therapy. For the treatment of such patients, electrodes are used, which, during a complex surgical operation, are implanted directly into the brain, which makes it possible to track the focus of seizures for several days. Scientists have developed a protocol for deep stimulation of the prefrontal cortex during restful sleep to enhance communication between the neocortex and the hippocampus.

Scientists synchronized stimulation of the prefrontal cortex with slow waves with a frequency of less than four hertz. Slow waves reflect the alternations between the burst of activity of neurons and their resting state and are believed to serve as a time frame for synchronization between the "ripples" in the neocortex and thalamocorcal sleep spindles - rhythms with a frequency of 9-16 hertz that occur during sleep in the thalamus and associated with it. areas of the cerebral cortex. This synchronization is considered to be critical for memory consolidation.

Before going to bed, volunteers were shown couples photographs of famous people and animals. When they were shown the images the next morning, those participants who received synchronized electrical stimulation while they were sleeping were better able to remember which images they had seen the night before.

The results of the study confirm the current dominant model of long-term memory consolidation, according to which the synchronization of rhythms in different areas of the brain provides a finely tuned connection between the human hippocampus and the human neocortex during sleep. Conversely, stimulation of the neocortex that was out of sync with the slow waves of the temporal brain worsened this connection.