Slow Wave sleep affects Memory Accuracy and Strength

Amy Taylor April 16, 2014

The sense of smell is one of the first things to fail in neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, and schizophrenia. In the new study, researchers from NYU Langone Medical Centre have found that memory of specific odours depends on the ability of the brain to learn, process and recall accurately and effectively during slow-wave sleep—a deep sleep characterised by slow brain waves.

They believe that a better understanding of how the brain processes odour information could lead to novel therapies that target specific neurons in the brain, perhaps enhancing memory consolidation and memory accuracy.

In their experiment on mice, odour memory was strengthened when odours sensed the previous day were replayed during sleep. Memories deepened more when odour reinforcement occurred during sleep than when rats were awake.

When the memory of a specific odour learned when the rats were awake was replayed during slow-wave sleep, they achieved a stronger memory for that odour the next day, compared to rats that received no replay, or only received replay when they were awake.

But when the rats were exposed to replay of an odour pattern during sleep that they had not previously learned, the rats had false memories to many different odours. When the research team pharmacologically prevented neurons from communicating to each other during slow-wave sleep, the accuracy of memory of the odour was also impaired.

The rats were initially trained to recognize odours through conditioning. Using electrodes in the olfactory bulb, a part of the brain responsible for perceiving smells, the researchers stimulated different smell perceptions, according to precise patterns of electrical stimulation. Then, they tested the effects of slow-wave sleep manipulation by replaying the patterns electrically.

"Our findings confirm the importance of brain activity during sleep for both memory strength and accuracy," says Dr. Wilson, the study’s senior author. "What we think is happening is that during slow-wave sleep, neurons in the brain communicate with each other, and in doing so, strengthen their connections, permitting storage of specific information."

According to Dr Wilson, these findings are the first to demonstrate that memory accuracy, not just memory strength, is altered during short-wave sleep. In future studies, they hope to examine how sleep disorders affect memory and perception.

Their findings were published in the Journal of Neuroscience.

Source of this article:

Slow-Wave Sleep-Imposed Replay Modulates Both Strength and Precision of Memory