14 DAY TRIAL // An international team of researchers, composed of experts from the Rutgers University, in Newark, the US, and the College de France, in Paris, has determined for the first time the nature of the mechanisms that take place in the human brain during sleep, which cause learning and memory to form. The scientific proof comes after almost a century of studies, in which researchers have hypothesized that sleep plays an important role in memory and learning, but have never been able to prove this conclusively.
The father of psychoanalysis himself, Sigmund Freud, believed that, whatever information and experiences the mind encountered during the day, the brain rehearsed during the night. In previous researches on the theme, it was proposed that a link had to exist between the brain region known as the hippocampus and the process of memory consolidation, but the exact mechanism through which this link became important was not understood.
Experts from the team were finally able to determine that in charge of converting short-term memories to long-term ones were transient brain events known as “sharp wave ripples.” These ripples essentially consolidate memory, and help transfer memory from the hippocampus, where it is temporarily stored, to a permanent location, inside the neocortex. A full study detailing the finds appears in the online September 11th issue of the famous scientific journal Nature Neuroscience.
In charge of the investigation was RU Center for Molecular and Behavioral Neuroscience Professor Gyorgy Buzsaki. Other investigators included College de France researchers Gabrielle Girardeau, Karim Benchenane, Sidney I. Wiener, and Michael B. Zugaro. They reveal that the intense, compressed oscillations that form the sharp wave ripples only occur during stage 3 and stage 4 of sleep, which is the deepest type of sleep a person can be in, with the exception of coma and death.
“It's as if many instruments and members of the orchestra come together to generate a loud sound, a sound so loud that it is heard by wide areas of the neocortex. These sharp, 'loud' transient events occur hundreds to thousands of times during sleep and 'teach' the neocortex to form a long-term form of the memory, a process referred to as memory consolidation,” Buzsaki says of what goes on during sleep.
“This is the first example that if a well-defined pattern of activity in the brain is reliably and selectively eliminated, it results in memory deficit; a demonstration that this specific brain pattern is the cause behind long-term memory formation,” the expert concludes.