We all do it.  We don't always do it well, or as much as we should, or on any sort of regular schedule, and humans do it differently than some other creatures. Not even all humans do it the same way, yet we still don't really understand its function, or why it's so critically important.

It's sleep, of course.  Despite the fact that it's been a universal of human experience for our entire existence as a species, it remains one of science's greatest mysteries.  What is its purpose?  Why did it evolve to claim a third of each person's lifetime?  What effect does its disruption or loss have on our health and well-being?

Penn Medicine is one of the world's premier research institutions exploring these questions.  It's doing so through a broad range of imaginative approaches, using research models ranging from round worms to humans, studying the enigma of sleep from nearly every conceivable angle. Penn researchers are focusing not only on the basic hows and whys of sleep, but also examining its relationship to other biological functions, finding intricate connections to eating and metabolism, cognitive functioning, fertility, and the development of neurodegenerative disorders.  Though we don't yet fully understand the reasons, it's clear that sleep is far from a luxury:  it's essential for life.


We tend of think of sleep as something done only by humans and other mammals: dogs, cats, humans. But although creatures with more primitive nervous systems don't sleep quite the same way as more complex animals, they do in fact display regular sleeping behaviors. Those behaviors – being studied by David Raizen, MD, PhD, assistant professor of Neurology, can provide important insights into the entire phenomenon of sleep in all animals. Read more.


One of the most exciting biological discoveries of recent years is the revelation of the many natural clocks that govern our lives. Rather than just a single "master clock" in the brain that controls our circadian rhythms of sleeping and waking, there are many other molecular clocks in the body's organs and even in some individual cell types that govern metabolism and other bodily cycles. Amita Sehgal, PhD, the John Herr Musser Professor of Neuroscience, discovered that the master sleep-wake cycle is intimately tied into these other rhythms, and when those rhythms fall out of sync the physiological dissonance created can have far-reaching consequences. Read more.


Losing sleep doesn't just make us feel sluggish, tired, and punchy. It also causes profound changes in the body that can lead to major health problems. Nirinjini Naidoo, PhD, research associate professor in the Division of Sleep Medicine, has shown that sleep deprivation can result in the unfolding and misfolding of proteins in the brain and in the cells of the pancreas, particularly as we grow older and normal repair functions such as the UPR (unfolded protein response) begin to break down. Read more.


We may not realize it because we're asleep at the time, but even during those nightly hours of unconsciousness, the brain is still at work. It repairs important neuronal connections, synthesizes vital proteins, performs cellular housekeeping, and prepares itself for another hard day of conscious functioning in a complex world. Studying the brain's night-time activity such as that in the lab of Marcos Frank, PhD¸ associate professor of Neuroscience, provides even more insights into the function and importance of sleep. Read more.


Is there a difference between going to sleep in your bed at the end of a long day and going to sleep under general anesthesia in the hospital? One is a natural process, while the other involves the administration of highly specialized, precisely measured and administered drugs. Do natural sleep and anesthesia operate through the same mechanisms? Do they have the same effects upon the body? Do different anesthetic drugs work in different ways? These are all questions that Max Kelz, MD, PhD, associate professor of Anesthesiology and Critical Care, is attempting to answer. The differences and similarities between these two states of consciousness can provide important clues into each. Read more.

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