Limbic brain

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The diagram below shows in more detail the components of the limbic brain.  These limbic structures sit above the reptilian brain.  It functions continuously, running the basic functions of the body and internal organs necessary for a healthy body.  Sensory input goes through the thalamus and limbic system before reaching the conscious brain (neocortex).

The olefactory lobes (the nose) is the only sense to go directly into the limbic brain (all the other senses go via the brain stem).  Smells can trigger memories and allergic reactions.  The amygdala is the centre of our emotions, and the hippocampus is where our long term memories are stored.  The limbic brain operates unconsciously – we have very limited ability to control or influence what goes on in this part of the brain.

brain-limbic

Limbic brain structures

A brief summary of the main components of the limbic brain.

Reptilian brainstem

brainstem

The brainstem is not actually part of the Limbic lobe, but it is worth covering the physical aspects of it briefly.  Together with the Limbic lobe, these brain areas are responsible for unconsciously running the entire physical body.  It runs the body for us, so we don’t need to think about it.

  • Medulla oblongata –  a sensory relay, with connectivity for some cranial nerves, and handles some important automatic reflex responses such as vomiting and sneezing.  Some spiritual sources consider the medulla to be the gateway to the superconscious, but it is hard to see where such a structure could be.  It is the gateway for the spinal and vagus nerves, so is the interface between the brain and the rest of the physical body.  Any damage to this important area is immediate death – shooting yourself through the mouth is likely to shatter the spinal cord near the medulla location and end your life immediately.
  • Pons – sensory relay, connectivity for some cranial nerves, and source nuclei for some neurotransmitters.
  • Midbrain – has connectivity for some of the cranial nerves and is the location for source nuclei for a number of important neurotransmitters.  The ventral tegmental area (VTA) is the source for dopamine for the inner brain areas.
  • Thalamus   – the hub through which all sensory input from the reptilian brain passes, and the centre for sleep, alertness and consciousness.
  • Cerebellum – regulates motor functions.  As we learn to move around we build up a library or stored learned procedures which we call upon, eg for walking, picking things up, eating, etc.  This is also the area for unconscious proprioception.

The Ascending Reticular Activation System (ARAS) is located in the brainstem.  This consists of interconnected nuclei that manufacture important neurotransmitters that control basic functions of the body including motor control, sleep/wake, pain, cardiovascular control, and habituation (filtering of irrelevant stimuli).

 

Limbic lobe

Limbic System

The limbic lobe has several important brain structures.  All operations within this lobe are completely unconscious.  That doesn’t mean it is dull or unintelligent – it means we aren’t consciously aware of all the things going on in the limbic brain.

Amygdala – emotional memory and unconscious decision-making (anger/fear).  This tiny structure has a huge influence on our lives.  Most sensory input from the Thalamus is passed by the amygdala for a “quick check”, and sometimes results in an emotional reflex response.  Normally, sensory information continues to the higher brain lobes, and decision-making in the orbifrontal cortex (OFC) provides the “off” switch to suppress mild reactions in the amygdala.  This is how we remain composed when confronted with unreasonable individuals – tolerance and compassion are the traits of spiritual people, who have developed their higher brain faculties to suppress the instinctive responses of the amygdala.

The so-called Amygdala Hijack is an automated reflex where certain extreme situations can trigger the amygdala and result in unconscious actions that bypass our normal rational thinking and decision-making in the conscious brain.  The theory is that it was a survival mechanism in our past, where quick reactions were necessary to save our lives – no time for the slow thinking/reasoning process to take place in the conscious brain.  In the world today there may be a few positive outcomes from this, but more often the result is negative.  A person can abruptly “snap” and react when threatened under stress, eg Zidane head butting Materazzi in the 2006 world soccer cup finals, reacting to taunting comments.  Road rage incidents are also often the result of the amygdala hijack.  Men have been known to “snap” when rejected by their girlfriend and kill her violently.  Once triggered the amygdala hijack state can last for 15 – 20 minutes.  When interviewed after the event the person often reports having no memory of what they just did – this is because it happened unconsciously.  Such a plea does not guarantee to get you off the murder charge!Interestingly, this unconscious “snap” may also be a mechanism for enlightenment in some individuals.

I read a report of a man returning home early one day to find his future wife in bed with another woman.  He said something went “snap” inside his brain, but instead of killing her he went in to a higher conscious state of enlightenment that lasted for several weeks, and was a life-changing event.  Such instances are very rare and almost impossible to study or replicate, but clearly the amygdala is capable of throwing a switch in the brain and using a different set of neural pathways.  Sometimes the shock can be positive, but I don’t recommend you rely on this method for your spiritual enlightenment.

Hippocampus – learning and memory (especially spatial memory and navigation).  This is a hugely important limbic area and how exactly it stores memory is not well understood.  There seems to be an area of intermediate term memory (several hours), then certain memories are filed away in the long-term memory store.  An excellent description of memory processes can be found here.

Cingulate gyrus – comprised of Anterior Cingulate (ACC) and Posterior Cingulate (PCC).  These areas are not well understood, but are involved in awareness, learning, and emotional processing.  The ACC is said to be involved in error detection and correction, as in learning about inappropriate interactions with others and adjusting behaviour accordingly.  The PCC controls our perception of pain and is involved with autobiographical memory.  These unconscious areas of the brain seem to be the seat of the personality we develop.

Pineal and Epithalamus – connects the brain to the endocrine system through the pineal gland which produces melatonin.  This is used by the Thalamus for regulating the sleep/waking cycle (circadian rhythms).   Taking melatonin can help the time zone adjustment and speed the recovery from jet lag.Some people (eg Rene Descartes) believed that the pineal gland was the gateway to enlightenment, but these claims have yet to be substantiated.  The pineal gland becomes less active after puberty and starts to atrophy.  Some believe that keeping the pineal gland active is key to gaining enlightenment.  In my view, a fully functioning endocrine system is but one of many facets necessary for spiritual growth.The mythology around Dracula, Vampires and the dependence on drinking blood is linked to melatonin and the pineal gland.  Melatonin is produced during the hours of darkness, but only seems to be important for regulating sleep patterns.  Garlic is said to cleanse the pineal gland (as well as keeping vampires away).  The naturally occuring drug DMT (dimethyltriptamine) is said to be produced in the pineal gland, and be the “spirit molecule“.  DMT is a powerful hallucinogenic drug, present in magic mushrooms and other shamanic preparations (eg ayahuasca) used for spiritual purposes.  (Paul McCartney said he used it and saw “God”).  It has a similar structure to serotonin and melatonin and binds to the same receptors in the brain.  It may deliver visions and altered states of consciousness, but the effects are short-lived and are not likely to be a path to enlightenment.

Hypothalamus and Pituitary – the hypothalamus connects the Limbic brain to the endocrine system view the Pituitary master endocrine gland, and is involved in the regulation of body temperature, hunger, thirst, fatigue and sleep (body homeostasis), etc.The pituitary gland produces serotonin and is involved in regulating growth, blood pressure, sex organs, thyroids and metabolism, pregnancy, childbirth, lactation, water/salt balance, temperature and pain relief.  There are two sides to the pituitary gland, anterior and posterior.  The depiction of  kings and queens in children’s fairy tales are said to be analogous to the way these glands function.  The King is the pineal gland; initially active but dies (the pineal function reduces after puberty) leaving the wicked queen (sometimes the wicked witch of the west) in the anterior pituitary ruling the kingdom (the body).  Without the intellect or reason provided by the King or the love of her sister (or the good witch of the east – the posterior pituitary gland which excretes the love hormones oxytocin and vasopressin) the wicked queen is cruel and harsh on her subjects (the physical body).  Only if the King awakes (pineal reactivates) or the Queen unites with her sister (both sides of the pituitary come into balance) can there then be peace and happiness in the kingdom.  I don’t know if fairy stories were written with this underlying knowledge, or if the authors are simply expressing what they innately know to be true.

Septal nuclei, nucleus accumbens and Basal Ganglia – the pleasure or reward centre for the brain.  There are many connections to this area from different parts of the brain, leading to positive reinforcement of actions forming habits and addictions.  Nearly everyone has some sort of addiction.  Many activities can lead to the “I like” response – drugs, high fat or sugar food, sex, physical activity, viewing pornographic images, music, etc.  There is a loop involving the higher cortex – basal ganglia – thalamus – nucleus accumbens releasing dopamine and other hormones, and the mechanism is slightly different for individuals that are introverts and those that are extroverts.  The reward path is significantly short for extroverts; for introverts the loop is longer and thinking processes can get involved.  It is much easier for introverts to free themselves from the trappings of the reward centre, and thus be able to meditate and focus on spiritual practices.

Perception of time – we all have quite an accurate clock in our subconscious brain.  This ability seems to be spread between a number of centres which record the passage of time with different levels of granularity.  There doesn’t seem to be a particular spot in the brain which is the clock but cells of the suprachiasmatic nucleus are involved in keeping the circadian rhythm.  It can be accessed to some degree, for example in the ability to wake from sleep at a particular time.  There are events which can cause the perception of time to change, for example to a person experiencing a life-threatening accident.  These experiences have been well documented but no satisfactory explanation for the mechanism exists.  Time also appears to slow down for some people during deep meditation.  This idea of hummingbirdtime slowing down was explored in Star Trek’s Insurrection where Captain Picard and Anji watched a Hummingbird’s wings beating in slow motion.  Dreaming isn’t well understood, but it appears that our perception of time is altered whilst we are dreaming – what can seem like a long detailed dream may in reality take place in just a second or two.

Eidetic memory – this is another proven but poorly understood human ability.  Often seen best in young children, this is the ability to memorise events with incredible detail.  For example, 14-year old Mozart was said to have transcribed Allegri’s Miserere perfectly having heard it performed once in the Cistine chapel.  Kim Peek has brain damage which impairs him in some ways, but has given him incredible memory skills.  Stephen Wiltshire appears to have a photographic memory for cities and landscapes.  We may all have these abilities but be unable to access them in our unconscious limbic brain.  There are several well documented cases showing that these savant-like memory abilities can develop suddenly following a brain accident (eg Orlando Serrell) suggesting that they were always there but previously inaccessible.  The development of these special abilities are usually at the expense of other social or motor functions, so it seems that whilst we may the ability to use the brain this way it is not intended that we do so.  Use of these abilities seems to be at the cost of our executive function abilities.
Before the advent of writing, the ancient religious texts (like the Vedas) were said to be handed down from generation to generation by word of mouth, memorised by particular gifted individuals.  Our executive brain functions seem to be developing at the expense of photographic memory.  The brain centres that may be used for Eidetic memory are not known, but the spatial memory capabilities of the Hippocampus or procedural memory functions of the cerebellum could be involved.  It may be that the Eidetic memories are stored instead in the Occipetal or Parietal lobes, prior to transfer to the Hippocampus for long-term storage.  It isn’t clear if it possible to develop these savant-type capabilities at the same time as our higher executive functions.

Gender identity – it appears that our preference for males or females (ie straight or gay sexual preference) may be locked away in the Hypothalamus.  This is not important for spiritual enlightenment.  Just note that if it is locked away in the Hypothalamus it isn’t something that can be “reprogrammed” or changed through conditioning.  It is the way you are.

Waking/sleeping (consciousness) – all sensory responses pass through the Thalamus which keeps a constant watch for danger, even when we are asleep.  There are many systems involved in the wake/sleep cycle and in creating the state of alertness in the body.  It has been suggested that the claustrum is the fundamental consciousness on/off switch.