This column appeared as “The Strange Riddle of Sleep” in the 25 October 2011 edition of The Beaver, the newspaper of the London School of Economics Student Union.
Understanding consciousness looms large in neuroscience as the holy grail. And indeed, comprehending how we are aware that we are aware has a certain audible allure to it. Francis Crick, who along with James Watson proposed the double helix structure of DNA, devoted most of his late life to neuroscience, seduced by its mystery and potential. Consciousness is deeply intertwined with both learning and memory, and together these topics form the trinity of popular inquiry in neuroscience. Yet for all the labor put into the endeavor, it’s often overlooked that we spend more than a third of our lives unconscious – that is, sleeping.
Despite the modern emphasis on consciousness, fascination with sleep has long cultural roots that extend through ancient Greece, more than 2,700 years ago. The Greeks, including Homer, fashioned sleep as deeply tied to death. The god of sleep (Hypnos) was known in mythology as a brother to Death and a son of the goddess Night. Socrates drew upon this relationship in claiming not to be afraid when the Athenians condemned him to death, saying that in the worst-case scenario, it would only be a deep, restful sleep. Another theme in ancient thought was to view sleep as a divine time, where gods and humans intermingled in the form of dreams. Robert Kennedy was fond of quoting the Greek tragedian Aeschylus in saying, “even in our sleep, pain that cannot forget falls drip by drip upon the soul, until…by the awful grace of God, comes wisdom”.
While sleep may seem odd in the abstract, it becomes downright bizarre when viewed through an evolutionary lens. How does sleeping possibly aid us in the eternal goal of avoiding predators and passing on our genes? It would seem to almost accomplish the exact opposite: a state of great vulnerability and no chance to reproduce. Yet sleep is widespread in the natural world – even fruit flies sleep. Despite this, researchers still haven’t figured out the purpose of this peculiar state that quantitatively dominates life moreso than any other activity. That the basic function of sleep remains a mystery is surprising given the colossal achievements of modern science – we have created a plausible theory about the origins of the universe, traced life back to its most primordial days on earth, synthesized the genome of a living organism, and with the advent of the Large Hadron Collider, are now smashing particles into each other at 99.999999 percent of the speed of light.
Yet despite its relative lack of glamour when compared with subatomic slugfests in Switzerland, sleep is science’s girl next door: easy to overlook at first, but more and more interesting over time. It has resisted easy answers – each theory proposed only begs more questions, both scientific and philosophical.
Established research has found that sleep is deeply tied to the body’s defense mechanisms, the immune system. Sleep patterns change during infection in order to help promote fevers. While fevers may feel bad, they are actually indicative of the body marshalling its forces to defeat invaders by preventing them from replicating easily (imagine trying to reproduce in a pot of boiling water and you’ll understand). This has led some to propose that immune function is the core necessity of sleep. Other research has found that sleep helps organize experiences and memories obtained while awake. In this way, sleep can be seen as a sort of biological housekeeping – we gluttonously eat up data about the world around us during the day, and only during sleep can we take a moment to cut out the unimportant and efficiently package things.
However, these experimentally valid results don’t answer the most basic question: Why do these processes need to occur during sleep? Sleep would seem to be a state of high vulnerability, so why didn’t the immune system and neural clean-up mechanisms evolve to accomplish their functions while we were conscious?
Another novel view is that sleep doesn’t actually really occur only on the level of the entire organism – you and I don’t sleep, parts of our brain do. For years, scientists thought that sleep was governed by certain brain structures that, like a totalitarian regime, forced the entire brain into sleep. But recent evidence makes sleep seem like more of a free market. Specific brain structures can sleep independently, and they produce the entire state we call sleep as a byproduct, or an “emergent property”. This puts sleep in a similar category to consciousness, which most neuroscientists think results somehow from billions of brain cells communicating with each other. According to this line of reasoning, after a particular set of cells is overworked, it tends to enter a sleep-like state. Doing this can slightly nudge other groups close to it to enter a sleep-like state as well.
One major question that emerges from this research is the identity of the actual sleeping unit. A couple years ago, researchers thought the answer was the cortical column, or large stretches of thousands of neurons in the cortex (the mysterious part of the brain that is likely responsible for human cognition). Recent evidence, however, shows that even individual neurons might sleep. As fascinating as this recent evidence is, it still raises the question of why sleep at the entire organism occurs at all, and why it evolved.
Perhaps the most provocative view is that propounded by Jerome Siegel of UCLA, which relies on concepts best known to basic economics: cost and benefit. Siegel changes some fundamental assumptions, “seeing the glass as half full rather than half empty”, as he told me in an email. Instead of emphasizing the lack of consciousness during sleep, Siegel highlights how much more quickly response times occur during sleep as compared to hibernation. He also challenges the view that sleep is a vulnerable state – perhaps, Siegel says, since scavenging for food is dangerous, sleep prevents us from doing this when the costs outweigh the benefits. The underlying thesis of Siegel’s theory, “adaptive inactivity”, is that sleep prevents inefficient behavior – when the costs of mating and finding food are higher than the benefits, sleep is a way to conserve energy and prevent needless action. While innovative, this theory is questioned by some in the scientific community, who, in Siegel’s words, “have been brought up on the idea of sleep as a mystery concept”.
Despite the difficulty of these queries, sleep research has a bright future, driven principally by NeuroVigil, a California-based company founded by Philip Low during graduate school at the Salk Institute in La Jolla. Dr. Low, a mathematician-turned-neuroscientist, overturned previously accepted wisdom in a 2007 paper that found human-like sleep rhythms in birds – significant given that researchers had previously thought the complexity of mammalian sleep was due to the neocortex, which is absent in birds. With NeuroVigil, Low extended his reach into the realm of brain monitoring, which is crucial to future breakthroughs in both sleep research and neuroscience in general. Traditional studies of sleep take place in a hospital, where patients have to spend the night hooked up to a cumbersome cap with many wired electrodes resembling a high-tech Medusa. Low’s revolutionary SPEARS algorithm made it possible to immediately analyze brain waves from just one electrode. The algorithm made it possible for his team to create the “iBrain”, a non-invasive wireless device that fits inside a tic-tac box and analyzes brain waves much more effectively than state of the art devices that are much bulkier. In fact, the data obtained by the iBrain/SPEARS duo is so good that researchers previously thought this sort of high-resolution data was only possible using electrodes that physically sat on the brain surface – meaning they had to be under the skull.
I interviewed Low, who was excited about the potential of his device to unearth the treasure trove of brain activity during sleep to make fundamental breakthroughs in neuroscience, including presymptomatic detection of diseases like Alzheimer’s, Depression, Epilepsy, Parkinson’sand Schizophrenia (among others), which have been shown to produce different patterns during sleep than the normal brain. Low has grand ambitions for the company, and many seem persuaded: he holds dual appointments at Stanford and MIT, and the company has won awards from the likes of the Washington Post and Fast Company, in addition to garnering a seed valuation for NeuroVigil more than double that of Facebook and Google combined.
Thus, the fascinating scientific queries on sleep may be primed for breakthroughs in the near future. Yet the philosophy of sleep poses questions that may resist easy answers. Why does one regain consciousness after a night of sleep, and why are they the same person when they wake up? Are they the same person? Is there even one “consciousness” that can be said to have continuity in the first place?
Researchers are working around the clock to dust off the cobwebs of our evolutionary past and unearth why this bizarre yet overwhelmingly common practice came to be. In the mean time, we’ll continue our daily lives, acting in each of our individual dramas, dealing with the strange realities of 21st century life. And every night we’ll retire, with only a vague trust that when it’s over -when the requisite mental machinations are finished, whatever they may be – we’ll wake up on the other side.
