Sleep and the unconscious brain

Our brain is the seat of consciousness, the organ that makes us self aware – cogito ergo sum!   But in fact, of the 80-100 billion neurons in the brain, it is only a small fraction that is accessible to our conscious awareness.  Much of what happens in this organ is below the surface where conscious awareness does not penetrate.   We are unconscious of the brain activities that control our heart or intestines or our breathing.  Likewise, we are also unconscious of the brain processes that control routine and well-learned activities like walking, riding a bicycle or driving – which is why we can perform such tasks even as our conscious mind is engaged doing something else, like speaking to someone.  But what may come as a surprise is how much of an influence unconscious brain function has on things that we regard as conscious decisions like choosing a flavour of ice-cream or choosing who we will marry!

Benjamin Libet in 1983 published the paper showing that the brain impulse that controlled a finger movement occurred hundred of milliseconds before conscious awareness of the decision to move the finger set in.   The will to act seemed to originate in the unconscious.  In subsequent behavioural experiments, psychologists have shown that subliminal cues (for which there is no conscious awareness) can reliably influence subsequent actions. For example, when subjects entered an office, seeing the picture of a library on a wall induced them to speak more softly or when there was a faint smell of a cleaning agent in the air they cleaned their desk more often.  It is becoming clear that the unconscious brain has a more significant effect on our behaviours than we realise.

Our sense organs continuously feed information in quantities that can quickly overwhelm the brain if all of it had to be consciously processed – the eyes alone feed in about 10 million bits of information per second.  Evolution has ensured that information not requiring our attention gets processed at an unconscious level and the appropriate action is triggered.  For this to happen the brain stores matches between incoming information and the corresponding actions  – in effect the unconscious brain operates like a heuristics engine.  Every now and then novel situational occurrences can disturb the equation between input and action.  For example, a bike rider unexpectedly encountering oncoming traffic must know to take appropriate evasive action.  How does the conscious brain take over from the unconscious brain in response to such atypical situations?

The prefrontal cortex is where executive decision making, planning, control of impulsivity etc. takes place – in some senses, it is a master regulator of actions triggered in the brain.  In the awake state, the prefrontal cortex is continuously monitoring sensory inputs and triggers the conscious brain to take over from the unconscious brain when required – as in the example with the bike rider above.  When we fall asleep, the prefrontal cortex becomes less active.  In the absence of the monitoring/censoring role of the prefrontal cortex, the unconscious is less restrained in the directions that it can take and every now and then this release from censorship takes the form of fantastic dreams.

The unconscious brain has evolved to be extremely efficient as a heuristics engine that can quickly form associations by matching sensory inputs to actions based on prior experience.  During sleep, in the absence of data pressure from sensory inputs, the heuristics engine is free to form novel associations.  Is it possible then that many of the creative insights that occur during sleep are a result of the unconscious brain acting independently to form novel associations?  This is a plausible hypothesis.  A similar process may also account for the fact that creative insights into problems during the awake state usually happen when the conscious brain is quietened, during tasks that are less demanding, e.g. having a bath or taking a walk or sitting in the back of a taxi.  Thus, William Hazlitt may have been on to something when he said  – “The definition of genius is that it acts unconsciously!”  Ramanajun, the Indian mathematician is famously known to have attributed his mathematical inspirations to dreams when he slept.  This is the subject of a small section titled “REM and Ramanujan” in my book Mastering Sleep.





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