Pillow talk

Exam tomorrow? Hit the sack early tonight

over time the one thing that has remained common amongst all animals is sleep. Even the evolutionary forces decided to leave this basic physiological need untouched. The various theories behind what makes sleep tick range from conservation of energy to a time for cell repair. Now experiments on the sleeping mechanism of the fruit fly, Drosophila, make obvious a known but unheeded fact: sleep gives the nervous system time to rejuvenate. A good night's sleep leads to an active brain.

Giorgio Gilestro with colleagues from the department of psychiatry, University of Wisconsin, usa, used various techniques to discover that sleep helps in reducing the levels of bruchpilot (the presence of which indicates a healthy synapse) and four other synaptic proteins in Drosophila.Synapse is the junction through which nerves communicate (via protein neurotransmitters) with various parts of the body.

The protein levels built up while the flies were awake but dropped 30 to 40 per cent during sleep, thus helping in renormalizing the synapses. Once the flies awoke the levels picked up. To further confirm that it is sleep and not any other parameter that causes this reduction, the team kept one batch of sleep-deprived flies awake and the rest were allowed to sleep. The batch that was awake continued producing high levels of synaptic proteins.

In a second study, Jeffrey Donlea and his team from the department of anatomy and neurobiology, Washington University, usa, examined specific neurons controlling sleep patterns in the fruit fly. "We have identified 16 neurons that are required for an increase in sleep," said Paul Shaw, from the Washington University and a member of the study team.

The studies, published in the April 3 issue of Science, also found the longer the flies were awake, the more hours of sleep they needed. "Different experiences induce different needs for sleep," added Shaw. In simpler terms, an overworked brain needs more sleep.