Friday, June 26, 2009

Sleep & Memory: “Replay” to Remember

A study published yesterday reports that the role of sleep in memory consolidation has been confirmed.

The study involved mice that ran a maze and then slept. Electrodes monitored their brain activity. While awake the brains of the mice “mapped” the pattern of the maze. Results show that their brains “replayed” this pattern during slow-wave sleep.

"Ours is the first study to demonstrate this link between memory replay and memory consolidation,” study co-author Susumu Tonegawa said in an
MIT statement. “The sleeping brain must replay experiences like video clips before they are transformed from short-term into long-term memories."

The study identified a specific circuit in the brain that is involved in this process - the “trisynaptic pathway.” It is located in the “hippocampus.” This is a complex brain structure that is shaped like a seahorse.

In some of the mice the trisynaptic pathway was blocked. This impaired the replay process during sleep. Only mice with a functioning trisynaptic pathway were able to form long-term memories of the maze.

"We demonstrated that this pathway is crucial for the transformation of a recent memory, formed within a day, to a remote memory that still exists at least six weeks later," Tonegawa said.

Read more about sleep and memory on the Sleep Education Blog. Learn more about the stages of sleep on

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