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By: Kent Caylor, RPSGT on April 26th, 2018

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The Changing Face of Sleep Technology: Part I

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.

In the rest of this article from the Q1 2018 issue of A2Zzz, Kent Caylor, RPSGT, goes into the milestones of sleep history, discusses the history of REM sleep and touches on early sleep labs. 

This article  is one of four designated CEC articles in this issue of A2Zzz. AAST members who read A2Zzz and claim their credits online by the deadline can earn 2.00 AAST Continuing Education Credits (CECs) per issue – for up to 8.00 AAST CECs per year. AAST CECs are accepted by the Board of Registered Polysomnographic Technologists (BRPT) and the American Board of Sleep Medicine (ABSM).


To earn AAST CECs, carefully read the four designated CEC articles and claim your credits online. You must go online to claim your credits by the deadline of June 8, 2018.

After the successful completion of this educational activity, your certificates will be available in the My CEC Portal acknowledging the credits earned.

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