Inside your mind at night

When in stressful, time-pressured situations often the last thing we prioritise is sleep, even if it is the thing we need most. Our innate ‘fight or flight’ response takes over – what was once used to flee from predators keeps us up late into the night reaching for that word count. Yet sleep is integral to health, as much as food and water.

Sleep is a vital opportunity for bodily rejuvenation, reflecting on the past day, processing our emotions and memory formation. Just take a look at Randy Gardner – the world record holder for spending the longest time without sleeping. After staying awake for 11 days and 25 minutes, he was asked to count back from 100 in intervals of seven. Randy stopped at 65; he had forgotten what he was doing.

Let’s assume that you are not Randy, and that you sleep on average eight hours every night of your 100-year life. By the end of it, you would have spent roughly 33 years in an altered state of consciousness that you will have no memory of, at least for the most part.

Now and again, we all have those dreams that we remember as vividly as though we lived them. In fact, some of the finest discoveries in history were elucidated in dreams. From Friedrich Kekulé, who envisioned the hexagonal structure of benzene as a snake chasing its tail, to Christopher Nolan who created his Blockbuster film ‘Inception’ in a lucid state; dreams have been a source of enlightenment for centuries. That should be enough encouragement for you to get your nightly eight hours.

I once read somewhere how odd it was that ‘in order to fall asleep, we pretend to be sleeping’. I mention this because most people do not ‘turn off like a light’, contrary to the popular saying. Normal sleep latency lasts 15-20 minutes and dreams only set in roughly 90 minutes after falling asleep. The time in-between is occupied by non-rapid eye movement (NREM) sleep, which can be broken down into three main stages.

In the first stage of NREM (NREM 1) you are teetering towards the edge of awareness, in a ‘hypnagogic’ state (from the Greek hupnos, meaning ‘sleep’, and agogos, meaning ‘leading’) from which you are very easily disturbed, even by physiological changes in your body. The ‘hypnic jerk’ is a phenomenon commonly experienced during NREM 1 that describes a startled wake from sleep, sometimes enhanced by the sensation of ‘falling in the void’.

Studies report that, on entering the hypnagogic state, your brain misinterprets muscle relaxation and dropping blood pressure as a sign of falling and stimulates muscle contraction in the hope that you can hang onto something. Professors at the University of Colorado proposed that such reflexes may be an evolutionary hangover from our tree-dwelling ancestors. In the past, these would have encouraged an individual to reassess their sleeping position, so they did not actually ‘fall’ asleep. This allegedly archaic response is reported more in those with elevated levels of caffeine, nicotine, anxiety and/or stress.

During NREM 2, most of your senses become detached from the environment whilst your core body temperature, breathing rate and heart rate all fall slightly, in a similar way to hibernating animals, albeit to a lesser extent.

On entering NREM 3, you experience deep, slow brain-wave sleep (SWS) in which your body resets its biological clock and recovers your physical health, in readiness for the next day. The energy reserves in your cells are restored, lactic acid (built up from the day’s work) is removed, tissues are repaired, and growth hormones are released. This may be the closest you ever come to whole body regeneration.

Finally, your brain activity starts to resemble that of someone who is awake. You are now entering rapid eye movement (REM) sleep, which is characterised by rapid brain waves, erratic breathing and heart rate, dreaming and muscle paralysis which prevents you from enacting the contents of those dreams. You cannot even pinch yourself to wake up. The importance of muscle paralysis during REM is well illustrated in people that suffer sleep behaviour disorders in which they violently act out their dreams (and nightmares!).

Once immersed in REM, there is little to no input from the external environment. Indeed, that is why we dream at all - the brain, which is usually packed with external stimuli, tries to make sense of its own activity. It is a type of ‘inception’ after all.

The actual rationale behind dreams remains a cognitive mystery; Freudian theory claims that it is an outlet for suppressed feelings; others claim that it has no biological significance whatsoever. Regardless, we forget as many as 95% of them anyway.

So, sleep well! Just don’t forget to wake up in time for your nine a.m. tomorrow!