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Response to external stimulus

Let’s look at things from a different perspective.  We are exposed all the time to external stimulus (even when we sleep our subconscious is still keeping a watch that our external environment is safe).  This is shown in the simplified human brain diagram below.

emotional response

Physical reflexes

Sensory input is received through eyes, ears, skin, etc.  It is fed to the brain stem and cerebellum (the reptilian brain), and quickly passed on via the thalamus and amygdala in the Limbic brain to the sensory cortex where the thinking brain can consider and react accordingly.  Generally the stimulus gets to the thinking brain, but there are emergency bypasses set up.  We have some 38 automatic physical reflexes.  When I was 3 years old I put my hand on the hot plate on the stove when it was hot.  I remember going to do it, and I remember my hand being bandaged afterwards; but I have no memory of the event.  It never got to my thinking brain as the protective reflexes came in to play.

Emotional reflexes

Similarly, there are some emergency overrides that the limbic brain uses.  The amygdala checks with some memorised scenarios in the hippocampus, and can initiate emergency action usually resulting in a fight or flight response.  This is useful if the recognition is a poisonous snake or crouching lion, but examples were also cited earlier where the amygdala hijack can take effect when a man get dumped by his girlfriend, for example, and he goes into a frenzy and stabs her 216 times with a pair of scissors.  Buried deep inside the limbic brain is the need to procreate, and loss of ones mate threatens this basic human desire.  Being buried deep inside the unconscious Limbic brain it is hard to reprogram this tendency, and fortunately is doesn’t happen in many individuals.

Back to the more usual emotional responses, external stimuli arrive at the sensory cortex and Default Mode Network in the thinking brain (frontal cortex), and it will already have an emotional colouring from its passage through the emotional brain.  The order of standard emotional responses are:

  1. surpriseSurprise – we are constantly looking out for changes in our environment, and the first emotional response is likely to be surprise when some aspect is different.  If you recall the discussion on emotions this causes us to back away and be cautious.  Surprise activates Dopamine and Norepinethrine which readies the body for action.  Surprise can lead on to the emotion of Anticipation, which reverses the back-off approach and results in us moving forwards.  Anticipation is all about Dopamine, and there are many activities that feed off this drug acting on the reward centre.  Sex, gambling, hunting, even listening to music (good music have melodies and lyrics that play on the mind anticipating what is coming next) are based on anticipation and the hormone Dopamine.
  2. fear.pngAnger/Fear – in emergency situations, surprise can be quickly superseded with the fight/flight/freeze response.  These are very powerful emotions, and are opposites of each other.  Fear releases adrenaline and cortisol into the body, whereas Anger releases Norepinethrine, testosterone, and reduces cortisol.  These hormones have a powerful effect on the body and we can react quickly and quite violently at times.
  3. Disgust – another protective basic emotion that causes us back away.  What disgusts one person can be very different from another person, and it all depends on how we have programmed our basic moral emotions.  Disgust causes the heart rate to slow and can result in a feeling of nausea and impact our digestive system.  The hormone progesterone appears to be linked to how likely something will disgust us.
  4. joy.pngJoy/Sadness – another two strong emotions.  These are opposites and are linked to the hormone Serotonin.  A reduction in our serotonin levels results in a feeling of sadness (pausing, stopping, doing less) and can lead to depression.  Elevated levels of serotonin results in us feeling happy and contented.  We are fortunate when the external stimuli results in us feeling happy.
  5. Another effect of external stimuli can be stress.  Stress resulting in physical or emotional pain can lead to the body producing endorphins, which are powerful chemical opioids that reduce our sensitivity to the pain.  Physical exercise can release endorphins, and being a powerful drug, we can get addicted to endorphins and the external events that cause their release.  Some teenagers suffering severe emotional or mental anguish will engage in self-harm, self-induced pain that leads to the release of endorphins that helps to counter both the physical and emotional pain; and it can become an addiction.

A positive effect of exercise on the body is to reduce the levels of cortisol, which is useful as prolonged periods of cortisol (from stress) suppresses the immune system making us more vulnerable to disease.  A bit of exercise is a good way of recovering from a bout of anger or fear.

These are the basic emotions that typically result from our interaction with the world through normal activities.  As these basic emotions interact with our thinking brains, the imagination of the DMN and our ego, a wide range of emotional responses result.

Higher-brain responses

It takes a good deal of self-control and personal development to engage the higher brain (Central Executive Network) functions, with a more considered and calculated emotional response.  In rare emergency situations, the salience network can bypass the lower thinking brain and directly engage the higher brain functions.  An example of this is the way we perceive time to slow down during a car accident.  This type of event doesn’t require an automatic physical or emotional response; instead all the energy of the brain is directed to cool, calculated thinking to help you survive – remove your seatbelt at the right time, move the head to avoid the looming impact, jump out just at the right time.

In normal situations, we need to be still and calm to reduce the impact of the ego, and invoke the higher brain functions.  Our subsequent reaction to external events can be delayed (seconds, instead of sub-second) as greater consideration is required.  This allows us to respond with emotions such as:

  • Trust – an emotion associated with the hormone oxytocin.  I have classified this as a higher emotion because it does require more calculated consideration of the persons or situation and usually a check with our moral emotions.
  • Compassion – empathy and compassion for other people seem to be centred in the supramarginal gyrus in the brain cortex.  No hormones involved here, just plenty of nerve connections through this brain area.
  • Self-sacrifice – often deeply thought out, but again the salience bypass can sometime come into affect during emergency situations, where a Mother may calmly sacrifice herself in order to save the life of her child.  This is the CEN in action.
  • Humility – absence of the ego, ie DMN is in the background.
  • Contentment – associated with elevated levels of serotonin.
  • Tolerance – may be associated with balanced levels of another neurotransmitter, GABA.
  • Non-attachment – this relates to having control over the reward system and the dopamine addiction pathways in the limbic brain.
  • Dispassion – whilst this can sometimes be viewed negatively, as in a person being cold and unfriendly, in the spiritual sense a dispassionate person is one who is free from personal feelings, biases and judgements.  Again, it is the ego and DMN taking a back seat to the CEN.

The point of this discussion is to show how we are likely to respond to the stimulus in the environment around us, and how we need to plan and be aware to ensure we are responding in the best possible way to assist our self-development.  Once again, getting our ego out of the way and getting the stimuli up to our higher brains, the CEN, for consideration and appropriate action is generally the best course.


As a side note, check out ASMR stimuli as it has recently become topical.