The definitive demonstration of the horrors of sleep deprivation appeared in a celebrated paper published by sleep research pioneer Allan Rechtschaffen and his colleagues in Science in 1983. They used rats.
What nobody had managed until then was to design a set-up in which both experimental and control animals received exactly the same conditions but different amounts of sleep. The solution Rechtschaffen and co. came up with is as ingenious as it is disturbing.
They installed a pair of rats in neighbouring cages. In the bottom of each cage was 3cm of water, but by standing on a record-player-like disk shared by both cages the rats were able to stay high and dry. The brains of both animals were wired up to an electroencephalogram (EEG) to record patterns of wake and sleep. Cleverly, the record player was controlled by the brain waves of the experimental rat. As soon as it fell asleep, the disk began to rotate at a leisurely 3.5 rpm.
“Whenever the disk was rotated, both rats had to walk in the direction opposite to the disk rotation to avoid being forced into the water,” wrote Rechtschaffen et al. So the animals were subject to the same environment and rotation, made to walk an average of almost one mile a day, but got very different amounts of sleep. Experimental rats got almost none, whilst control rats were able to grab some rest when the experimental rats were spontaneously awake and the turntable was stationary. “This study is best viewed as a comparison between severe and moderate sleep deprivation,” they wrote.
With time, the severely sleep deprived rats began to deteriorate, showing at least two of several pathological signs, including ungroomed fur, skin lesions, swollen paws, inability to move, loss of balance and significant weakening of the EEG signal. Three of eight experimental rats died, one after just five days. When Rechtschaffen and co. carried out necropsies on the deceased they found evidence of further problems, including collapsed lung, stomach ulcers, internal bleeding, testicular atrophy, severe scrotal damage and swollen bladder. The control rats, by contrast, were in relatively good nick.
The conclusion: “Sleep does serve a vital physiological function.”