Sleep Science
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This is the Sleepy History of Sleep Science, narrated by Arif Hodzik, written by Ivan Suazo. Humans have been fascinated by the mysterious nature of sleep for millennia. Our curiosity has led to several groundbreaking studies, from the discovery of REM sleep to Stanford University's colony of narcoleptic dogs. However,

Thousands of years before these discoveries, ancient Egyptians built magnificent temples along the Nile River where the restless went to dream. We'll visit one of these temples and then travel to the Age of Enlightenment where touch-me-nots helped to advance the science of circadian rhythms. So just relax and let your mind drift

as we explore the sleepy history of sleep science. Sleep is a vital part of our daily routine. It's essential for the proper functioning of the human body. During sleep, the body undergoes various processes. One is the repair and rejuvenation of tissues. This is important to wake up the following day

feeling refreshed and renewed. Another critical function of slumber is the consolidation of memory during the deep stages of sleep. Our brains are busy storing and organizing information we learned. This is crucial for long-term memory retention and learning. Other benefits of sleep include increased attention span,

improved mood, reduced stress, and a stronger immune system. But when and how did humans start studying sleep in earnest? We know that getting a good night's rest is essential for our health. But have you ever wondered what actually happens when we sleep? Let's travel back 4,000 years to ancient Egypt to answer these questions.

The banks of the Nile River were crucial for settlements, agriculture, and trade in ancient Egypt. The river provided fertile soil for farming, a source of food and water, and transportation on boats made from papyrus and reed. In essence, the Nile River was the very foundation of Egyptian civilization.

with adjacent structures ranging from simple mud brick homes to grand pyramids. Some structures along the river were temples or shrines dedicated to the gods and goddesses of ancient Egypt. They were not only places of worship, but also centers of art, culture, and medicine.

Some of the temples were built specifically for the restless, known as sleep temples or sanatoriums. One of the most famous sleep temples still standing today is the Dendera Temple of Hathor, located on the western banks of the Nile River. The Temple of Hathor is a breathtaking example of ancient Egyptian architecture.

The colossal earthen brown structure has a flat roof, sloping side walls and massive columns with beautifully preserved reliefs or carvings. These carvings can be found throughout the temple walls and in the various chambers and halls where light and shadows create an ethereal atmosphere.

They depict Egyptian gods and goddesses, pharaohs, and members of the ancient nobility in exquisite detail. Some figures wear a nemesis headdress with horizontal stripes in a serpentine style. Other miniature figures sit on their haunches with their heads bowed in reverence and their arms outstretched.

They offer grains, fruits, and vegetables to the gods. Today, visitors can explore the temple complex, which consists of various mud brick structures, chambers, and halls. One of the most visited structures is the Mamisi, or birth house of the Egyptian sky god, Horus.

The Mamisi resembles the main temple. It has the same earthen brown hue, except it is smaller and only partially finished. The Egyptian god Horus is often depicted as a loinclothed man with the head of a falcon. His right eye is the sun, representing power, and his left eye is the moon, representing healing.

However, one of the most commonly found reliefs through the Temple of Hell shows Horus with the face of a man. This relief, which is called the Dendera Light, is arguably the temple's most famous artwork. It shows Horus as a young man sporting a serpentine nemesis.

and holding a light fixture shaped like a tulip. The beam it emits contains a slithering snake. Beneath him, ancient Egyptians celebrate the serpent's emergence from the light, clasping their hands in prayer. Ancient Egyptians viewed serpents as symbols of protection, healing, fertility,

and immortality. Although the reliefs may be fascinating to behold, a sleep scientist would perhaps be most interested in exploring the temple sanatorium known as the sanctuary of Isis. It comprises a separate structure with its own brick perimeter well and imposing entrance to the east.

The sanctuary resembles an ancient Roman ruin and has a maze-like quality with parapets fashioned out of large and thick rectangular mud bricks. The structure pays tribute to Isis, a prominent Egyptian goddess associated with motherhood, fertility, and healing.

The sanatoriums of ancient Egypt were bathhouses where the sick and injured could be treated. They were often located near sacred waters, in Dendera's case, the Nile River. The sanctuary of Isis was a place where people could seek spiritual healing too.

It was staffed by priests who were trained in the art of medicine. It is believed that, in some cases, these spiritual healers observed their overnight patients closely. They recited prayers to induce healing and helped manifest dreams via hypnosis.

They believed these dreams could offer their patients guidance in real life. Still 4,000 years ago, humanity lacked the technology and resources to study sleep in depth. It took thousands of years for sleep science to reach a major milestone since the first sleep sanctuaries of ancient Egypt.

One of the earliest significant studies during the age of enlightenment did not involve human participants whatsoever. Instead in 1729, French physicist observed the curious sleep-wake cycle of the mimosa pudica.

otherwise known as the touch-me-not or shy plant. Touch-me-nots are perennial plants found in tropical regions. They have thin stems and their pink flower heads look like dandelion orbs. They're famous for folding their green leaves inwardly when touched. However,

Demeron noticed that the touch-me-not's leaves would also fold up daily around dusk and then unfurl around dawn. He theorized that the plant's ability to close its leaves wasn't just a defense mechanism against predators, but also a response to changes in life.

he conducted an experiment to test whether the plant exhibited the behavior without any physical stimulus. In the experiment, de Meuron kept a few touch-me-nots in a dark cupboard. Despite daylight's absence, he noticed the plants continued to open and close their leaves on a 24-hour cycle.

The touch-me-nots would open their leaves at dawn and fold them at dusk. It seemed as though the plants had an internal clock telling them when to open and close their leaves. This discovery was a significant contribution to the understanding of circadian rhythms. These 24-hour cycles are found in many living organisms,

including humans. They're crucial for regulating many physiological processes such as sleep wake cycles, hormone production and metabolism. Alone cannot fully explain the complexity of sleep. Other factors such as environment and lifestyle also play a crucial role in

in determining a person's quality quantity of sleep. Even the slightest shift in body temperature can disrupt one's sleep. As British physician, John Davy noted in 1845, John Davy was a doctor and chemist from England's Southwestern region of Cornwall.

He earned his medical degree from Edinburgh University in 1814 and later served as the Inspector General of hospitals for the British government. Throughout his career, Davy conducted numerous experiments. He made important contributions to the fields of chemistry and medicine.

establishing himself as a prominent figure in science. A black and white portrait of Davey available on Wikipedia shows the scientist in his middle age, sporting sideburns and an archaic smile. One notable discovery was Davey's observation that even a slight increase in body temperature

can make it difficult for a person to fall and stay asleep. His 1845 article on the temperature of man addressed this discovery. It was published in the philosophical transactions of the Royal society of London. In the article, Davey expressed his feelings right from the beginning when he wrote,

It has been too generally taken for granted that the temperature of man in health as measured by a thermometer placed under the tongue is a constant one. Self-experimentation was growing in popularity at the time. It was considered an effective way for scientists to learn about the human body. So to prove his point,

Davy conducted a series of self-experiments. He used a 12-inch thermometer whose 1-inch bulb measured his temperature. The bulb was curved so that it faced him every time he took his temperature. When there was low light in his study or carriage, he would hold up a magnifying glass to the bulb to make it easier for him to record the number.

Overall, it was an unusual experiment to test the effects of exercise on body temperature and sleep quality. Davy donned his gentleman's hat, breeches, and waistcoat and speed walked from his home to the nearest church. Once at the church, he would place the thermometer under his tongue and jot down his temperature.

In another experiment, Davey noticed a possible correlation between exposure to cold air without exercise and drowsiness. Despite wearing warm clothes one freezing winter, he noted that he experienced a sensation of disagreeable chilliness. A feeling of drowsiness was also perceived.

Davey wrote in the article. He compared it to the body temperature of a hibernating animal, such as a bear or a groundhog, or to quote Davey again, a prelude to sleep resulting from long exposure to severe cold without exercise. In short, the feeling of drowsiness that Davey described

was similar to what one might experience at the movie theater, cozy in a reclining leather seat. In yet another curious experiment, Davey investigated the effects of excited and sustained attention on bodily temperatures. He found that one's temperature increased and one's pulse accelerated during a period of excitement.

He arrived at this conclusion chiefly by recording his temperature while reading for pleasure versus reading for intellectual stimulation. Davey recorded an average body temperature of 97.92 degrees when reading for pleasure. On the other hand, when reading for intellectual stimulation,

his temperature averaged 98.4 degrees. Given these differences in average temperatures, Davey argued that reading for amusement had a sedative influence on the body rather than an exciting one. In other words, reading for intellectual stimulation kept him awake, whereas reading for fun made him sleepy.

Davey felt drowsy and lethargic consistently in temperatures around 97 degrees Fahrenheit, regardless of whether it was day or night. Interestingly, Davey's experience aligns with current sleep research. It is a commonly known fact that the body temperature drops by about 1.8 degrees during sleep.

almost a century after Davies self-experimentation, another groundbreaking study took place in 1924, a German psychiatrist named Hans Berger became the first to record human brain activity using an electroencephalogram or EEG machine that he himself invented back then.

Dr. Berger looked every bit the scientist in his white double-breasted lab coat, black work boots, and trimmed mustache. His laboratory was located at the University of Jena in central Germany. The university's architecture reflected the classical style of the time.

with half-timbered stone facades and arched multi-paned windows. In his laboratory, Berger recorded the brain's electrical currents, which he called alpha and beta waves, by connecting electrodes to the scalp of his subjects. He used a string galvanometer similar to the needle on a record player

to record the brain waves on a light sensitive plate. First, he measured the brain activity of an alert non-sleeping subject. The parallel images produced on the plate horizontally resembled the jagged peaks and valleys of a mountain range. The peaks and valleys of the uppermost range comprising the beta waves

were invariably more condensed than the alpha waves below. We now know beta waves involve conscious thought and logical thinking in humans. They maintain a higher frequency level in an alert state than alpha waves. By contrast, the undulating alpha waves are associated with a relaxed meditative state

and are characterized by a lower frequency. It stands to reason then that alpha waves would increase in frequency during sleep. However, when measuring the brain activities of sleep subjects, Berger made an exciting discovery. He found that alpha waves vanished completely, further shrouding the science of sleep in mystery.

It would take a few more decades to understand why. And we'll get to that in a moment. Meanwhile, the scientists from across the pond established the world's first sleep laboratory at the university of Chicago. His name was Dr. Nathaniel Kleitman, a Russian emigre whose life's work was devoted to studying sleep.

Kleitman furnished his lab with infirmary-style cots, white bedsheets, and a lab bench. The cots and bedsheets created a suitable sleeping environment for the research subjects, enabling Kleitman to study their sleep patterns.

Various instruments, including electrode machines and other measuring devices he and his students designed, littered the bench. It was in this unusual setup that Kleitman and another scientist, Dr. Eugene Osirinsky, made a groundbreaking discovery that would revolutionize the field of sleep research.

In 1953, Kleitman and Azarinsky discovered rapid eye movement, or REM sleep. To the two scientists, the constant swiveling of the eyeballs during sleep indicated dreaming. They found that individuals who were awakened during periods of REM sleep were able to recall their dreams.

whereas those awakened during non-REM sleep could not. By 1958, Kleitman and another scientist, William C. Demond, had established that the human sleep cycle consists of alternating periods of REM and non-REM sleep. Kleitman and his associates further argued

that most dreaming took place during REM sleep and that a healthy full night's rest occurred in five stages. These stages were then standardized in 1968 in the decay sleep scoring manual, further solidifying a five stage consensus among sleep scientists. Stage one, non-REM,

also known as N1 is the initial stage between wakefulness and sleep. It usually lasts around 10 minutes during this stage, your heart rate breathing, eye movement and muscle relaxation slow considerably. Stage two non-REM also called N2 is a phase of light sleep

that occurs before entering a deeper sleep stage. It typically lasts 20 minutes during stage two, your heart rate and breathing slow, even further. And your brain generates brief bursts of rapid rhythmic brainwave activity, sleep spindles stages, N three and N four,

are the last stages of non REM sleep. During these phases, you experience one of the deepest levels of sleep, which lasts between 20 and 40 minutes, your heart rate and breathing slow to their lowest levels. And your muscles become so relaxed that it might be difficult to wake you up.

These stages and three and four are vital in promoting physical and cognitive restoration, including muscle repair and growth, memory consolidation and learning stage five REM sleep is the final stage before repeating the sleep cycle. It typically occurs 90 minutes after sleep onset,

and is the deepest stage of sleep. It is characterized by rapid eye movements, near complete body paralysis or atonia and a tendency to dream vividly. Humans typically spend 75% of their sleep time in non-rapid eye movement or NREM stages.

A typical night consists of four to five sleep cycles and one cycle takes about 90 to 110 minutes to complete. Today, the science of sleep is a thriving industry with many researchers studying its various aspects. Studies range from sleep disorders and deprivation

to the effects of sleep on mental health. Significant advances in technology such as sleep trackers and magnetic resonance imaging or MRIs have enabled researchers to gain a better understanding of the physiology of sleep. Advanced imaging can even explain the disappearance of Berger's alpha waves

As it turns out, the slow undulating waves Berger recorded alongside the more condensed beta waves are still present in the brain when we sleep. It's just that they're drowned out by the brain's even slower theta and delta waves, which modern EEG machines are able to capture.

These waves are typically recorded during the third and fourth stages of sleep, known as slow wave sleep. So, where beta waves resemble sharp peaks and valleys, like the Himalayan range, theta and delta waves are like the rolling hills of Tuscany, gentle and soothing.

yet still with a sense of movement and energy. Delta waves are the slowest and loudest brain waves with a deep penetrating sound like a drum beat. They're generated in deep meditation and dreamless sleep. This deep restorative sleep stimulates healing and regeneration,

making it essential to the recovery process. In addition to their intentional research efforts to understand what happens when we sleep, some scientists have made accidental discoveries. Take melatonin for example. In 1958, researchers at Yale university

were studying a substance from the pineal gland in the brain to treat skin diseases. Their subjects were not humans, but dairy cows. While extracting the substance from the cow's pineal glands, they found the hormone melatonin. They discovered that the production and release of melatonin increased in the dark

and decreased when exposed to light. This is why it is known as the sleep hormone and is widely used today as a natural sleep aid. 15 years later, a number of sleep studies conducted at Stanford University led to the first successful genetic transmission of narcolepsy. Narcolepsy is a sleep disorder

characterized by excessive daytime sleepiness. It is also marked by sudden and uncontrollable episodes of falling asleep during the day. In some cases, those afflicted with narcolepsy experience a sudden loss of muscle tone known as cataplexy triggered by strong emotions such as laughter or surprise. So,

someone might tell a joke and the narcoleptic person finding it way too funny may doze off shortly after laughing. In 1973, sleep doctor William C. Demond, who helped establish the five stages of sleep alongside Dr. Nathaniel Kleitman, visited veterinarians in more than 50 US cities

He and his associate, Dr. Merrill M. Midler also spoke at many US colleges of veterinary medicine. The researchers were able to identify a small number of animals with narcolepsy from various breeds, including poodles and beagles. Two years later in 1975,

three Dobermans with narcolepsy, two of which were related, were donated to the canine colony so that doctors Demand and Midler could study them further. Breeding the dogs resulted in a litter of affected Dobermans born in Stanford the following year. Afterward, multiple cases of Labradors with narcolepsy were also reported.

Demond and Midler found that the trait was transmitted as a single autosomal recessive gene. In other words, the affected dogs had to inherit a copy of the gene from both parents in order to exhibit the symptoms of narcolepsy. Other animals have inspired sleep research too.

Though not always in controlled environments such as laboratories and clinics, enter Dr. Michael Bruce. At age 31, became one of the youngest fellows to join the American Academy of Sleep Medicine. In 2016, Dr. Bruce observed the sleeping patterns of various animals.

His research enabled him to classify humans into four chronotypes based on their unique sleep wake cycles. While his theory provides a way of thinking about someone's sleep preferences, it hasn't been scientifically proven. A chronotype is a person's natural inclination of when and how they prefer to sleep.

It also hints at the time of day when they are most active within a 24-hour period. The four sleep chronotypes are lions, wolves, dolphins, and bears. According to Dr. Bruce, lions are early risers who feel most productive between 9 a.m. and 2 p.m., a typical in the life of a lion chronotype.

usually involves waking up around dawn and exercising before breakfast. This chronotype also prefers to tackle essential tasks during the morning hours and wrap up the day around 9 p.m. with some leisure activities before 8-10 p.m. bedtime.

Dr. Bruce estimates that roughly 15% of people are lions. The wolf chronotype, however, couldn't be more different. Wolves, like owls, are nocturnal creatures. They enjoy sleeping in whenever possible and have a peak productivity period from 1:00 PM to 5:00 PM or even later.

They tend to experience bursts of creativity at night, painting, writing, or playing an instrument until it's time for bed around midnight. According to Dr. Bruce, another 15% of humans can be classified as wolves. So where do light sleepers fit into these diverse categories?

Let's take a quick dip in the ocean and find out our planets, oceans, and seas house dozens of dolphins species from sleek bottle nosed swimmers to the spotted dolphins of the Caribbean. These intelligent mammals are known for their playful nature, social behavior, and impressive communication skills.

Perhaps a lesser known fact is that dolphins sleep unihemispherically with only half their brain active at a time. The right eye will be closed when the left half of the brain sleeps and vice versa. This enables dolphins to stay alert to potential dangers even while resting. Unfortunately,

This also means dolphins are ultra sensitive to the faintest sounds and disturbances in their environment. Their sleep is irregular with power naps taken sporadically throughout the day. Despite their relatively limited sleep compared to humans, dolphins still managed to complete important tasks effectively.

outsmarting many Marine predators in the process. Dr. Bruce believes about 10% of people are dolphin chronotypes. The remaining 50% of humans fall into the bear chronotype category. This means they have a standard sleep wake cycle with active mornings and a sluggish afternoon period.

They tend to feel most alert and productive in the late morning and typically gain a second wind after lunch. However, their energy levels and cognitive abilities tend to dip in the evening, making it harder for them to stay focused and engaged during nighttime activities. Bedtime for the bear chronotype.

is usually around 11:00 PM. It's clear that the science of sleep has revealed a lot about how humans and animals doze off and why it's essential for good health and wellbeing. Nowadays, the business of sleep has also become a profitable industry. Many companies manufacture sleep related products

such as eye masks lined in silk or satin for extra comfort and mattresses that come in a box. Others produce content to aid the sleep process, including the story you're listening to right now. The spotlight on mental health has impacted the way humans fall asleep with many people turning to meditation, yoga,

and other relaxation techniques to help them sleep better. This is good news. It shows how people are becoming increasingly aware of the importance of sleep. We take steps to improve our sleep quality. We prioritize it so that we awaken the following day feeling refreshed and ready to take on the day's challenges.

While sleep science has come a long way since the dream temples of ancient Egypt, there is still much to learn about the complex processes involved in sleep. Researchers continue to explore the various aspects of this fascinating topic. In time, it's important to do our part by creating a comfortable sleep environment. Ideally,

This is a cozy room where our bodies can sink into plush mattresses and the gentle hum of the fan lulls us into a peaceful slumber. Our brains remain active, pulsing with slow wave sleep. And this final stage, our dreams become vivid, spurring our imagination and transporting us

to other worlds.