Fragmented sleep can lead to memory problems

Interrupted or fragmented sleep may lead to memory problems, a new study suggests.

The study findings may partly explain why conditions such as sleep apnoea, Alzheimer's disease and alcoholism, which also cause sleep disruptions, can lead to memory impairment.

Scientists at Stanford University were able to unravel what specific characteristic of sleeping affected memory. Poor quality sleep, stress, lack of sleep and time spent sleeping have all been linked to memory problems.

Using mice, the researchers used a new technique, known as optogenetics, in which specific cells are genetically engineered to be controlled by pulses of light.

The technique allowed them to target the brain cells that play a key role in switching between being asleep and being awake.

By stimulating the cells with 10 second pulses of light, they could interrupt the animals' sleep without affecting total sleep time or the quality and composition of sleep.

The animals were then placed in a box with two objects: one of which they were already familiar, and another that was new to them.

Mice have a natural tendency to explore new objects, so if they spent more time with the new object, it would suggest that they remembered the other familiar object.

However, the mice in the disrupted sleep group were equally interested in both objects, suggesting that their memory was affected. Mice which had slept normally were more interested in the new object.

In the journal Proceedings of the National Academy of Sciences they wrote: " We conclude that regardless of the total amount of sleep, a minimal unit of uninterrupted sleep is crucial for memory consolidation."

This article was published on Tue 26 July 2011