Ivory Towers: Falling asleep on the job

THE ELEVENTH European Congress on Sleep Research, held last year in Helsinki, has provided some surprising information on why we need sleep.

In their paper The effects of sleep deprivation on divergent thinking and attention processes (Journal of Sleep Research Vol 1, 1992), F Wimmer, R F Hoffmann, R A Bonato and A R Moffitt point out that 'in spite of the fact that research on sleep deprivation has been performed for nearly 100 years . . . surprisingly little has been concluded from such efforts.' Experiments have shown that vigilance and reaction time are impaired by sleep loss, but no definite pattern has emerged for thinking tasks.

The present researchers found a difference between the sleep-deprived subjects and a well-rested control group, not on their initial performance of a task, but on a subsequent re-test. So if you are tired, you can still concentrate well enough to perform a thinking task once, but your performance will subsequently deteriorate. Without sleep deprivation, you will perform better the second time.

If you are a rat, however, you might find it hard to perform at all, especially if your mother was deprived of sleep during her pregnancy. That surprising result is reported by J Velazquez-Moctezuma in his paper REM Sleep deprivation in pregnant rats induce sexual behaviour impairments in offspring (Journal of Sleep Research, Vol 1, 1992, Helsinki supplement). In his experiment, pregnant rats were awoken whenever their eyelids fluttered rapidly.

This Rapid Eye Movement (REM) sleep has long been associated with dreaming in humans, and several experiments have suggested that it is essential for getting 'a good night's sleep'. Humans who are deprived of REM sleep are liable to wake up as tetchy as those who have not slept at all.

With rats, however, the problems are passed on to the next generation. For these experiments showed that male offspring of REM sleep-deprived rats showed a marked impairment in sexual behaviour. Their 'mounting frequency' was higher than normal, but these attempts were marked by a lack of success.

It was concluded that whatever was the precise effect of the mother's REM sleeplessness, it 'affects the ejaculatory mechanisms instead of the motivational aspects of copulation.' Female offspring showed no analogous problems, apart from a lower fertilization rate.