Stages of sleep have distinct influence on process of learning and memory

February 25, 2009,

Research on the sleeping brain has revealed some fascinating stage-dependent interactions between areas involved in formation and storage of long term memories. The study, published by Cell Press in the February 26th issue of the journal Neuron, may also provide a framework for further understanding the role of sleep in memory.

Mammalian sleep occurs in two discrete stages, slow wave sleep (SWS) and rapid eye movement (REM) sleep. One of the many ways in which SWS and REM sleep differ is in the level of synchronous firing in the hippocampus. Previous research has suggested that coordinated activity between the hippocampus (a brain area critical for memory formation) and the neocortex (where long-term memories are stored) may be critical for memory formation.

"Given the importance of synchrony and spike timing in synaptic plasticity, and given the putative role of sleep in learning and memory, a key question is whether consistent spike timing relationships exist across cortico-hippocampal circuits during sleep, and whether these differ in SWS versus REM sleep," explains senior study author, Dr. Athanassios G. Siapas from the California Institute of Technology. Dr. Siapas and colleagues used sophisticated recording and computational techniques to examine the activity of neurons in the hippocampus and prefrontal cortex in sleeping rats.

The researchers observed highly consistent directional interactions between the hippocampus and neocortex during SWS, but only during discrete bursts of activity in the hippocampus known as "ripples", suggesting that these bursts may represent a basic unit of information transfer. There was a non-linear relationship between the magnitude of hippocampal signals and the patterning of prefrontal responses, suggesting that variations in the strength of hippocampal bursts may lead to qualitatively different cortical responses.

Interestingly, the coupling between the hippocampus and prefrontal cortex was greatly reduced during REM sleep. Previous computational models of memory consolidation have supported a need for gradual transfer of memory traces from the hippocampus to the neocortex and for a reorganization of memory traces without external input. The current findings suggest that transfer and reorganization may be met by SWS and REM sleep, respectively.

The researchers went on to speculate that the disconnection between the hippocampus and prefrontal cortex during REM sleep may explain some of the persistent mysteries associated with REM sleep. "It's possible that the scarcity of coordinated cortico-hippocampal spiking during REM sleep may explain why the awake-like neural activity in the prefrontal cortex during REM does not interact strongly with the hippocampus and therefore why dreams are, on the whole, forgotten," offers Casimir Wierzynski, a graduate student in Dr. Siapas's lab and lead author of the paper.

Source: Cell Press

Explore further: With wrist-worn gadget, researchers capture real-life sleep for the first time

Related Stories

With wrist-worn gadget, researchers capture real-life sleep for the first time

December 28, 2017
To measure a person's sleep, researchers have always relied on costly and time-consuming approaches that could only be used in a sleep lab. But now researchers reporting in Current Biology on December 28 have found a way ...

Researchers use optogenetics to trigger REM sleep in mice

December 30, 2014
Getting enough of the right kind of sleep is crucial for keeping both body and mind healthy. Now a team of researchers at MIT has moved a step closer to being able to produce natural sleep patterns.

New insights into REM sleep crack an enduring mystery

October 22, 2015
REM sleep—the phase of night-time mammalian sleep physiology where dreams occur—has long fascinated scientists, clinicians, philosophers, and artists alike, but the identity of the neurons that control REM sleep, and ...

Poor REM sleep may be linked to higher risk for anxiety, depression

February 9, 2016
(HealthDay)—REM (rapid eye movement) sleep is the phase when dreams are made, and a lack of good REM sleep has long been associated with chronic insomnia.

New role of adenosine in the regulation of REM sleep discovered

September 1, 2016
The regulation and function of sleep is one of the biggest black boxes of today's brain science. A new paper published online on August 2 in the journal Brain Structure & Function finds that rapid eye movement (REM) sleep ...

REM sleep critical for young brain development; medication interferes

July 3, 2015
Rapid eye movement or REM sleep actively converts waking experiences into lasting memories and abilities in young brains reports a new study from Washington State University Spokane.

Recommended for you

Study looks at how newly discovered gene helps grow blood vessels

February 19, 2018
A new study published today found that a newly discovered gene helps grow blood vessels when it senses inadequate blood flow to tissues.

Scientists produce human intestinal lining that re-creates living tissue inside organ-chip

February 16, 2018
Investigators have demonstrated how cells of a human intestinal lining created outside an individual's body mirror living tissue when placed inside microengineered Intestine-Chips, opening the door to personalized testing ...

Data wave hits health care

February 16, 2018
Technology used by Facebook, Google and Amazon to turn spoken language into text, recognize faces and target advertising could help doctors fight one of the deadliest infections in American hospitals.

Researcher explains how statistics, neuroscience improve anesthesiology

February 16, 2018
It's intuitive that anesthesia operates in the brain, but the standard protocol among anesthesiologists when monitoring and dosing patients during surgery is to rely on indirect signs of arousal like movement, and changes ...

Team reports progress in pursuit of sickle cell cure

February 16, 2018
Scientists have successfully used gene editing to repair 20 to 40 percent of stem and progenitor cells taken from the peripheral blood of patients with sickle cell disease, according to Rice University bioengineer Gang Bao.

Appetite-controlling molecule could prevent 'rebound' weight gain after dieting

February 15, 2018
Scientists have revealed how mice control their appetite when under stress such as cold temperatures and starvation, according to a new study by Monash University and St Vincent's Institute in Melbourne. The results shed ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.