Sleep, the ally of the brain, helps certain brain functions like energy restoration for brain cells and memory consolidation. The sleep is regulated mainly by circadian rhythms and homeostasis. The interactions between the circadian rhythms and homeostatic mechanisms influence the timing, duration and quality of sleep and wakefulness. The circadian rhythms regulate the timing of sleep. Homeostasis ensures that the body acquires over time the necessary amount of sleep. It prompts a person to sleep when he or she has not slept enough, and also wakes people after enough sleep.

The researchers are not sure about the molecular mechanism of sleep or why one benefits from sleep or why one feels tired due to lack of sleep. If one understands the regulatory mechanism of sleep, this could lead to interventions to alleviate pathologies associated with sleep disturbance. Learning more about the genetics of sleep in model animals can possibly lead us to better understand human sleep, and how sleep loss affects the human condition.

The researchers at the University of Leicester say that the fruit-fly Drosophila melanogaster shares striking similarities with mammalian sleep. “For example, sleep in the fruit fly can be modulated by chemicals such as caffeine, and is characterised by a reduced arousal following sleep deprivation. In older flies sleep becomes shorter and fragmented.”

A study by scientists at North Carolina State University found that, on average, male fruit flies sleep longer than females; males sleep more during the day than females; and males are more active when awake than females. Females, in turn, tend to have more frequent bouts of sleep, and thus are disrupted more from sleep. Another observation of their study was that a group of genes appear to act together to affect some portion of sleep. In this study minute-by-minute activity of the fruit fly was monitored using infrared sensors. If at least five minutes passed without any fly activity, it was calculated as sleep. The study conducted at the University of Kentucky identified changes in the brain that lead to the increased desire and need for sleep during time spent awake.

Zebra fish is known to have similar sleep related behaviour as in humans. Harvard scientists observed that many of the pathways found in humans are conserved in fish. Researchers developed a screening tool that tests the effects of thousands of compounds on zebra fish behaviour in an effort to discover new pathways that govern sleep. The outcome of this research may result in new drugs to treat insomnia and other sleep-related disorders.

Scientists at the University of California at San Francisco have discovered gene involved in regulating the optimal length of human sleep. “Short-term and chronic disruptions in the length of optimal sleep can have serious consequences on cognition, mood and physical health, including cancer and endocrine function,” say researchers. The researchers identified a mutation in a gene (hDEC2), which regulates circadian rhythms. Based on this information, the scientists engineered mice to express the mutated gene. The engineered mice slept less. Further studies on the impact of sleep deprivation revealed that the engineered mice were less affected by the loss of sleep than its normal counterpart. This observation can possibly explain why some of us are unaffected by shorter sleep.

The writer is a biotechnologist and ED, Birla Institute of Scientific Research, Jaipur