Four Stages Of Sleep

They are 4 separate stages that the brain goes through in sleep.

The first stage starts with closing our eyes and relaxing. This involves reduced activity of our brain waves (such as beta waves that appear on charts as are a series of short, tightly-spaced teeth - like serrated edges of a bread knife). The peaks of activity become slightly larger, more regular and more spaced out compared with when we are awake; this involves going from

"...alert wakefulness into a gentler, more rhythmic sequence of pulsed activity, like the hum of distant machinery. This is a shift from beta to alpha wave activity..."

Robert Winston, 2003

Still part of the first stage of sleep is the theta wave formation

"...Theta waves are less regular, more like handwriting on the paper roll of the EEG (electro-cardiographic) machine. We can be easily aroused from this stage of sleep and may not even be aware that we are asleep. While this is going on, we may see vivid images before our eyes - sometimes a version of what we may see in the room as if we were awake. We may experience sudden jolts in our arms and legs - which sometimes wake us with the sensation that we have fallen to the earth with a sudden bump..."

Robert Winston, 2003

During the second stage of real sleep, breathing becomes more regular and we are harder to wake. Theta wave activity is still present with occasional bursts of activity, called "sleep spindles" and "k-complexes"

The last two stages of sleep are associated with delta wave activity (high and low patterns with regular peaks and troughs). We are increasingly oblivious to our surroundings, and if woken suddenly, feel startled and disorientated. On the other hand, we are still receptive to particular sounds, such as a parent being instantly aroused when she/he hears a child crying.

After around 90 minutes of sleep, the cycle goes into reverse, ie rapidly going back to stages 3 and 2, and then 1. Then we move into the rapid eye movement sleep (REM) or paradoxical sleep as there is a contrast between our sleeping body and our alert mind. In fact, some areas of the brain, such as the brain stem, are more active during this stage than in our normal waking state. If woken during this REM sleep, most people will say they have been dreaming; while if woken during non-REM sleep, fewer people will claim to have been dreaming. Furthermore, the types of dreams are different, ie

"...non-REM dreams have a procedural nature - for example, performing dull, day-to-day activities, like typing, or dialling numbers of the telephone. REM dreams, by contrast, are a more fantastical mixture of reality and the outright bizarre. They can involve intense emotions, illogical events and a suspension of the normal rules of time and space. Familiar people may turn into strangers, and vice versa......the sleep cycle repeats itself throughout the night (or whenever we are sleeping) - becoming shorter as we move towards the appointed hour of the alarm clock. As the cycle shortens, more time is spent in REM sleep. We may pass through this cycle to the point of actually waking up several times a night, but if our brain is healthy and there is an absence of distracting stimuli, we will go back to sleep and not remember these intervals..."

Robert Winston, 2003

NB The most refreshing form of sleep occurs when lying horizontal

It is estimated we sleep for around 24 years during our lifetime. If he went straight into deep sleep with increased our waking hours by 13 years. Researchers are investigating how to launch the brain directly into deep sleep by using transcranial magnetic stimulation. "...a recent survey in Silicon Valley found 15% of CEOs were using the kind of smart pills that are largely banned to help them outperform their competitors..."

Chris Sanderson as quoted by Patrick Durkin 2016d

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