For the first time, researchers pinpoint brain activity in the hippocampus responsible for long-term memory
A Rutgers University, Newark and Coll-ge de France, Paris research team has pinpointed for the first time the mechanism that takes place during sleep that causes learning and memory formation to occur.
It's been known for more than a century that sleep somehow is important for learning and memory. Sigmund Freud further suspected that what we learned during the day was "rehearsed" by the brain during dreaming, allowing memories to form. And while much recent research has focused on the correlative links between the hippocampus and memory consolidation, what had not been identified was the specific processes that cause long-term memories to form.
As posted online September 11, 2009 by Nature Neuroscience, Gy-rgy Buzsaki, professor at the Center for Molecular and Behavioral Neuroscience at Rutgers University, Newark, and his co-researchers, Gabrielle Girardeau, Karim Benchenane, Sidney I. Wiener and Micha-l B. Zugaro of the Coll-ge de France, have determined that short transient brain events, called "sharp wave ripples," are responsible for consolidating memory and transferring the learned information from the hippocampus to the neocortex, where long-term memories are stored. www.nature.com/neuro/journal/vaop/ncurrent/abs/nn.2384.html
Sharp wave ripples are intense, compressed oscillations that occur in the hippocampus when the hippocampus is working "off-line," most often during stage four sleep, which, along with stage three, is the deepest level of sleep.
During stage four sleep, Buzsaki explains, "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." The intensity and multiple occurrence of those ripples also explain why certain events may only take place once in the waking state and yet can be remembered for a lifetime, adds Buzsaki.