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By: Kent Caylor, RPSGT on February 19th, 2020

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The Changing Face of Sleep Technology: Part 1

Sleep Technology Trends | Sleep technology | history of sleep technology

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A Brief History of Polysomnography

The earliest recorded theory of sleep is from c450 BC. At that time, a Greek physician by the name of Almaeon described sleep as a loss of consciousness as blood recedes from the surface of the body¹. A few other theories came out regarding sleep. However, all theories encompassed a similar theme: Sleep was seen as a passive state in which the brain was simply “turned off.”

In other words, sleep was something that happened to the brain, as opposed to the brain taking an active part in initiating sleep.

In this article, we’ll take a trip back through time and see how we got from these earliest theories of sleep to the development of polysomnography.

To get a better understanding of polysomnography, it is imperative we look at two branches of research that helped in its development. These two fields encompass both the study of the nervous system and an understanding of electricity. In the following sections, we’ll take a brief look at these two fields as they relate to the growth of polysomnography.

The Study of the Nervous System

Our knowledge of the nervous system evolved through several stages. Early thought was that the nerve itself was like a hollow tube. Early practitioners postulated that it was this hollowness that allowed the “animal spiritus” to flow through it. And it was this flow of the animal spiritus that created movement.

Another thought was that, yes, the nerve was hollow, but it was water, not spirit that flowed through it. Therefore, water pressure caused movement. It wasn’t until scientists began to actually dissect the human cadaver that a clearer understanding of the nervous system came about.

So, although ancient practitioners had a basic understanding of what the nervous system did, they didn’t know how it worked. They also questioned whether nerves originated from the heart or the brain. For instance, Aristotle believed that the heart was the first organ of the body, and therefore the seat of all motion and sensation.²

We now know, however, that the nervous system is a complex communication system. It starts with the brain and has an amazing pathway that would stretch out to 60 miles.

The Study of Electricity

Back in the late 18th century, an Italian biologist by the name of Luigi Galvani made a startling discovery. He was dissecting a frog when his steel scalpel came in  contact with a brass hook. At that very moment, the frog leg twitched. It twitched, he reasoned, because of electric current within the frog muscles. Something he called “animal electricity.”

After that, an Italian physicist by the name of Alessandro Volta replicated the results   of Galvani’s experiments. However, Volta drew a different conclusion. The frog leg twitched, Volta reasoned, not because of some “animal electricity,” but simply because the frog’s leg came into contact with two different metals. And Volta was right in this case.

However, Galvani did eventually prove “animal electricity.” And it was this discovery that living tissue generates an electric charge that paved the way for the discovery of brain waves. Although it wasn’t until the 18th century that physiologists made the connection between electricity and the nervous system.

It is these two scientific fields that form the basis for the study of sleep.

Milestones in Sleep Medicine

1875 – Richard Caton discovered the electrical nature of the brain and studied the electrical activity of animal brains. He also published what is believed to be the first account of brain waves.

1880 – Narcolepsy is recognized. The name is derived from two Greek words: narke, meaning numbness or stupor, and lepsis, meaning attack or to seize.

1907 – Two French physiologists, Legendre and Pieron, experimented on dogs. One of these experiments involved injecting blood serum from sleep-deprived dogs into non- sleep-deprived dogs. They found that the blood serum-induced sleep in the non-sleep- deprived dogs.

1913 – French Scientist Henri Pieron wrote a book titled “Le probleme physiologique du sommeil,” translated “The Physiological Problem of Sleep.” His work is considered the beginning of the modern approach to sleep research.

1925 – Physiologist Nathaniel Kleitman, known as the father of modern sleep medicine, set up the first lab exclusively devoted to the study of sleep.

1929 – German psychiatrist Hans Berger “discovers” electroencephalography, or EEG. Using his 15-year-old son as a test subject, he recorded the first human brain waves. The first waves he witnessed were with his son’s eyes closed, so he called them Alpha waves. He had his son open his eyes, and noticed a different type of signal. Because this was the second type of signal to be observed, he named them Beta waves.

1953 – REM sleep is discovered by Dr. Nathaniel Kleitman and his student Eugene Aserinsky. Up until this time, sleep was seen as a passive state, one in which the brain merely “switched off” for the night. The thought was that the brain needed outside stimulus to maintain wakefulness.  With the lack of outside stimulus to put it to sleep, the brain itself was taking on a passive role. But the discovery of REM sleep changed that perception. We’ll discuss this more in the next section.

1965 – Obstructive Sleep Apnea (OSA) is defined.

1968 – “A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects” is produced by Alan Rechtschaffen and Anthony Kales.

1975 – Dr. William Dement forms the Association of Sleep Disorder Centers (ASDC). The name was later changed to the American Academy of Sleep Medicine (AASM).

1978 – A small group of people gathered in Minnesota and formed the Association of Polysomnographic Technologists (APT). This organization was created with the goal of developing a professional identity, as well as define standards and provide training for polysomnographers. The name of this organization was later changed to the American Association of Sleep Technologists (AAST).

1981 – Continuous positive airway pressure (CPAP) was invented by Dr. Collin Sullivan of Sydney, Australia, as a treatment for sleep apnea. The first CPAP masks were individually molded to the patient and held on with adhesive. Until then, the standard treatment for OSA was a tracheotomy.

More on the Discovery of REM Sleep

“People usually see only what they expect to find, and they do not see what they assume for whatever reason could not exist.” —Dr. William Dement

It turns out that REM sleep was discovered quite by accident. In fact, When Eugene Aserinsky first saw it, he and Dr. Kleitman thought it was artifact. Thus, they actually ignored it for a few nights.

The reason they were so quick to assume these real eye movements were merely artifact is, in part, due to the quality of the equipment they were using at the time. The early Offner Dynograph was notorious for initiating pen movements, even when no patient was hooked up.³

However, they eventually decided to go in and physically observe the eyelids of the test subjects to see if their eyes were, in fact, moving. And of course, it turned out they were. This was a very significant finding. Initially, Aserinsky wanted to call these “jerky eye movements.” Also, when he measured them, they were not only more jerky then wake eyes, they were also slightly slower.

However, the slang meaning of the word “jerk” at the time caused Aserinsky to shy away from using that term. If he hadn’t been so slang sensitive, we’d now be using the phrase jerky eye movements, or JEMs, which, as it turns out, is actually a more accurate term for this type of eye movement.

Another interesting phenomenon that occurred during REM sleep was the activation of the cerebral cortex. In other words, the brain actually looked like it was awake, indicating that sleep was not a passive state after all. This discovery totally revolutionized sleep research. In fact, it was this discovery that turned the study of sleep in to a real science.

However, these REM periods were not initially associated with dreaming. Therefore, the next step was to study them a little closer to see what they meant. Enter William Dement, a student of Dr. Kleitman’s and a self-described aspiring psychoanalyst. When Dr. Dement was told that REM periods might be related to dreaming, he got pretty excited.

The reason for his excitement was due to the influence of Dr. Sigmund Freud’s theory of dream interpretation. In Freud’s own words, dreams represent “the royal road to a knowledge of the part the unconsciousness plays in mental life.” So, unlocking the meaning of dreams was huge. Thus, Dr. Dement was delighted when he was asked to sit up all night and watch people’s eyes move. If people were actually dreaming during REM periods, the implications could be quite significant.

Part of the experiments involved waking people during these REM periods and asking if they were, in fact, dreaming. Through these experiments, it was shown that REM periods were indeed associated with dreaming.

Thus began the study of sleep.


Early Sleep Labs

Sleep studies were initially recorded on analog polygraphs, which used paper and ink. However, these analog polygraphs were actually quite reliable. In fact, a sleep study rarely had to be rescheduled due to equipment failure. For example, a pen or galvanometer, even an amplifier, could be replaced on the fly, and you’d be good to go.

Another nice thing about those old analog polygraphs was the sound of the pen on paper. Each waveform had its own unique intonation. For instance, the sound of a cardiac arrhythmia could alert a technologist whose attention might be on something else at the time.

However, there were many problems that came with these machines. To begin with, they used paper … lots of paper. For example, two sleep studies could use enough paper to require over a cubic foot of storage space. Plus, these studies had to be saved for seven years. Besides that, the polygraphs themselves were huge. They measured 5 to 6 feet in height and weighed a couple hundred pounds. Then there were the paper cuts and ink stains.

We’ve come a long ways in our journey through sleep medicine. But we have a ways to go. In the next article, we'll take a look at where we are now.

This article was originally published in the A2Zzz Quarter 1, 2018


  1. howsleepworks.com/research.htm
  2. http://web.stanford.edu/class/history13/earlysciencelab/body/nervespages/nerves.html
  3. http://www2.semel.ucla.edu/sites/default/files/sleep/pdf/96-rem-discovery-aserinsky.pdf