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Last Updated: Saturday, 18 March 2006, 00:22 GMT
Sleep loss 'harms route memory'
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Spatial memory works in a similar way in rats and humans
Losing sleep can interfere with the part of the brain responsible for finding your way round, a study says.

US researchers found rats that were deprived of sleep had difficulty navigating a maze.

Restricting sleep interfered with the rats' spatial memory - responsible for recording information about the surrounding environment, the team said.

But UK experts were divided over the findings published in the Journal of Neurophysiology.

Spatial memory is essential for rats and humans to remember familiar environments, people use it to find their way round a city, while it is used by rats in hunting for food.

I don't believe spatial learning is harmed by sleep deprivation. Research has suggested that it depends what task people are asked to do
Professor Jim Horne, of the Loughborough Sleep Research Centre

The team took two groups of rats, putting one in a water maze where they could not see or smell the exit.

The rats were repeatedly put in the maze again once they had slept with some being allowed to sleep for six hours longer than others.

Researchers found the rats which had more sleep produced more cells in the hippocampus part of the brain, which is responsible for spatial learning as it is in humans, and were better at finding their way out.

The second group were also put in a maze, but were allowed to see and smell the exit - the door was scented with citrus - which was moved every fourth trial.

Senses

In this group, the sleep deprived rats performed better. The researchers said this was unexpected and suggested the sleep deprived rats were quicker to use their senses because their spatial learning was impaired.

Lead researcher Ilana Hairston said as well as proving sleep deprivation affected spatial memory, the suggestion was that sleep did not affect senses.

"This may be significant in human learning as well and implies that it may be possible to optimise the way information ins presented to rested versus fatigued individuals to take advantage of the specific neural substrates that are unaffected by sleep loss."

She added this could specifically help medical and military training and further research could be carried out to see if sleep loss affected other brain and memory functions in a similar way.

But UK experts remained mixed over whether sleep affected spatial learning.

Professor Jim Horne, director of the Loughborough Sleep Research Centre, said it would be wrong to assume rats and humans would react in similar ways.

And he added: "I don't believe spatial learning is harmed by sleep deprivation. Research has suggested that it depends what task people are asked to do. If it is boring, sleepy people just switch off, but don't do the same for exciting tasks."

However, Dr Neil Stanley, of the University of Surrey, said sleep loss harmed spatial learning, although the brain could rise to the "spatial learning" challenge in the short-term it would struggle eventually.




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