Continuing on from the previous blog, there, quite typically at this point, occurs evidence of change, different to anything witnessed hitherto. The EEG pattern returns to small and rapid oscillations; the EMG line also flattens out, whereas the EOG now begins to record quite distinct movement of the eyes, known as Rapid Eye Movement (REM) sleep. This is the dreaming stage (although it is known that dreaming can and does occur sometimes outwith REM sleep).

What I have just described may be defined as one complete “cycle” of night sleep, i.e. stages 1, 2, 3 and 4, followed by REM sleep and in which, slow wave or Delta sleep has – at least in the earlier part of the night – featured prominently, with a much smaller proportion of overall time being devoted to REM sleep and dreaming. An entire night’s sleep is likely to consist of around five such complete cycles. However, as the night progresses, the predominance of slow wave sleep and sparsity of dreaming (witnessed at the beginning) increasingly changes to a point of reversal, i.e. toward the end of the night, slow wave sleep is only very occasionally in evidence, with predominance being given to REM sleep.

In terms of what we experience when we sleep, we might say that every night we enter a very mild state of hibernation: body temperature drops a whole degree, breathing and heart rate is slowed and many bodily processes are placed on a kind of ‘back burner’. Levels of the stress hormone cortisol, are also reduced although the converse is true of growth hormone. Increasing REM sleep and dreaming toward the end of the night prepares the body for waking i.e. temperature rises, breathing, heart rate, cortisol levels etc., return to normal, all heralding an approaching end to sleep.

Let me make it abundantly clear at this point in the letter that I possess no  actual ‘hands-on’ experience in sleep research. Indeed, the closest I have ever been to it was during a solitary visit to a “sleep laboratory”, while attending meetings on the Continent, which also afforded a valuable opportunity to converse with one of its foremost researchers. Merely am I briefly reporting what (I hope to show) is so beneficial for each one of us to know of what others have painstakingly and systematically ‘garnered’ while working in the “sleep research” field. And I do so because I consider it to be so very important to possess an understanding of sleep, at least to the point where we can better and more successfully manage, i.e. cope with, both our waking and sleeping states.

I shall therefore conclude this blog with a brief account of what we have come to learn about the manner in which our brains’ manage and regulate sleep, in the interests of survival and continuing good health. This, I trust, will be both interesting and enlightening and pave the way for a further blog that I intend to write on sleep, providing simple but practical suggestions of a, hopefully, supportive and beneficial kind, in order to improve, possibly the quantity and certainly, the quality of night sleep. Questions like, “What is sleep for?” “Why do we dream?” “Why and how do substances such as drugs or alcohol or (as we shall see in the next blog) certain foods affect sleep?” all testify to the key role played by the brain. However, in pre-scientific days, the brain was generally regarded to be playing only a marginal role. Lucritius, a poet from Roman times maintained that sleep was an entirely passive process, a corollary one might say of the working state. The one time eminent Professor of Surgery and Physiology named Philipp Franz von Walther, expressed a different view. He claimed that sleep represents “A surrendering of the egotistical being to the…natural spirit” and “A flowing together of the individual human soul with the universal soul of nature”.

This view of the brain’s passive role in sleep prevailed until the 1930s. Walter Hess, working in Zurich (and later, a Nobel prize-winner in medicine) found that by implanting tiny electrodes into the brains of cats (the brain is not sensitive to pain) he could induce sleep for long periods of time). Any detailed account of this work lies well outwith the scope of these blogs. Sufficient is it to say that Hess and other contemporaries laid to rest for all time the notion that the brain is passive in sleep. Thus the view of complexly integrated brain function in sleep was established; i.e. a ‘waking’ brain and a ‘sleeping’ brain, not as two organs but as two functional states within the one organ. These Hess named the “ergotropic” state (from the Greek meaning “tending toward work”) and the “trophotropic” state (Greek for “nourishing and replenishing”).

Reference has already been made to the manner in which the body and brain functions via a complex and potentially ever-active series of electrochemical impulses. Thus – and as things transpired – it was and is the chemical component which proved to be decisive in distinguishing between the ‘working’ and ‘sleeping’ brain (since there appears to be no single locus or site within the brain relating exclusively to sleeping or waking). Most nerve cells within the brain fully maintain their potential for activity whether the subject is asleep or awake. However, what is different in these two latter states is the pattern of “firing”. Messages passing throughout the brain and body are relayed by electrical charges across a tiny gap existing between two nerve cells (known as a synapse)· and the nature of that message is determined by the composition of the chemical (neurotransmitter) substance released into that gap at the precise moment of firing.

The manner in which pharmacological and biochemical research ‘took off’ – at times at breath-taking speed – is also a subject matter well beyond the scope of this present work. Sufficient is it here to state that sleep appears to be regulated according to the balance between these chemical (neurotransmitter) substances and how they interpret their function. Chief among them is serotonin, along with other building materials of protein molecules and even endogenous sleep substances. (The latter are on-board substances, i.e. produced naturally within the brain and body) and we shall return to say a further word about serotonin in my next blog. In the meantime, you will, I am sure, be relieved to know that we have come to the end of this particular posting, although in all truth, it attempts to no more than simply describe something about what must surely be the commonest experience known to man, i.e. sleep. In my next, I shall consider ways in which how, in our day-by-day lives, we might use the understanding implicit in the above to more adequately respond to our need for sleep. This we shall do via the adoption of simple strategies and practices aimed at enhancing its overall input to well-being and quality of life. (C) SB.