Wake up with the fly behind the ear

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In a study of the fruit fly, the researchers have identified a “thermometer” circuit that relays information about external cold temperature from the fly antenna to the higher brain. They show how, through this circuit, seasonally cold and dark conditions can inhibit neurons within the fly brain that promote activity and wakefulness, particularly in the morning.This helps explains why it is so hard to wake up in the morning in winter.By studying behaviors in a fruit fly, we can better understand how and why temperature is so critical to regulating sleep.The paper describes for the first time “absolute cold” receptors residing in the fly antenna, which respond to temperature only below the flies comfort zone.Having identified those neurons, the researchers followed them all the way to their targets within the brain.They found the main recipients of this information are a small group of brain neurons that are part of a larger network that controls rhythms of activity and sleep.Drosophila is a classic model system for circadian biology, the area in which researchers study the mechanisms controlling our 24-hour cycle of rest and activity.Part of the reason humans seek optimal temperatures is that core and brain temperatures are intimately tied to the induction and maintenance of sleep.The principles we are finding in the fly brain, the logic and organization,may be the same all the way to humans. Whether fly or human, the sensory systems have to solve the same problems, so they often do it in the same ways.The ramifications of impaired sleep are numerous:fatigue, reduced concentration, poor learning and alteration of a myriad of health parameters;yet we still do not fully understand how sleep is produced and regulated within the brain and how changes in external conditions may impact sleep drive and quality.