link: triune
THE THREE-LAYERED OR 'TRIUNE' BRAIN
Theme: The characteristic functions of the human brain are the natural outcome of millions of years of evolutionary process through natural selection. The brain is three-layered or 'triune'. The three major layers or 'brains' were established successively in human evolution... first the reptilian brain or 'R-complex', the second the mammmalian brain or 'limbic system', and the third the neo-mammalian brain or 'neocortex'. Each has a separate function and depending on the circumstances each can become dominant but all three layers interact in the processing of information i.e. cognition or learning. The triune brain paradigm has forced a rethink of brain functioning or 'brain/mind'.
"As a product of human evolution through natural selection, the brain can best be understood as an organ of learning, adapted for the survival of the species". (Gerald Fischbach, Mind and Brain, Scientific American, 267: 3, Sept 1992, 48.)
Dr. Paul McClean... reptilian complex... mammalian brain... neo-mammalian brain or neocortex...
"The brain is best understood in terms of three functioning units: alertness, information processing, and action" (Restak The Brain)
Dr. Paul Maclean: evolutionary development of the brain neurologist Dr. Paul MacLean (director of the Laboratory of Brain Evolution and Behaviour in Poolesville, Maryland) was originally interested in philosophy and 'converted' to the study of science and medecine while taking a course in the philosophy of science... as director of the Laboratory for Brain Evolution and Behaviour of the National Institute of Mental Health in the 1960s MacClean expanded on the work of James Papez... and conducted research on the assumption that observations of the behaviour of animals are relevant to the understanding of the behaviour of humans. MacLean studied the evolutionary development of the nervous system and described the human brain as a a three part concentric layering structure or 'triune' brain. Each of the three brain layers represents a distinct evolutionary stratum that has formed upon the older layer before it like an archeological city. The oldest layer is the reptilian brain, 'reptilian system' or 'R-complex', the second oldest is the paleomamalian brain or 'limbic system', seat of emotions and autonomic nervous system and the most recent is the neomammalian brain or 'neocortex' the seat of thought and voluntary movement. Each of the three brains is connected by nerves to the other two. Each has a separate function but all three layers interact... the three layers of the human brain operate like "three interconnected biological computers, each with its own special intelligence, its own subjectivity, its own sense of time and space and its own memory". Each brain operates as its own brain system with distinct capacities for perceiving and responding to the environment and each can become dominant depending on the circumstances.
Integration and coordination between the three brains is inadequate, a genetic problem in our species... This has implications for human development.
Reptilian system or R-complex The 'reptilian system' is the oldest layer... the most 'primitive' of the three brain components and makes up the entire brain mass in reptiles. The reptilian system, also known as the primitive (reptilian) brain, or 'basal brian'... 'archipallium', 'root brain' or 'R-complex'. The R-complex consists largely of the structures... brain stem medulla, pons, cerebellum, mesencephalon, the oldest basal nuclei - the globus pallidus and the olfactory bulbs...the 'basal ganglia', the 'reticular activating system' and the 'midbrain'. Functions of the R-complex are related to physical survival and body maintenance - digestion, reproduction, circulation, breathing, stress responses, territorial instincts, social dominance.... Functions related to the instinctive behaviour patterns of self-preservation include 'primitive' behaviours... responsible for automatic behaviours associated with territoriality, ritualism, social dominance, status maintenance, deception, tendency to follow precedent, awe for authority, social pecking order behaviour, compulsiveness, deception, prejudice and resistance to change... rigid, obsessive, compulsive, and paranoid. The functioning of the R-complex is activated when the organism perceives threat and the needs for survival and safety predominate. This part of the brain is active, even in deep sleep.
Mammalian brain or 'limbic system' the paleopallium or intermediate (old mammalian) brain.The second layer middle part of the brain occupies the lower fifth of the human brain... the 'mammalian brain' ... 'paleomammalian brain'...'limbic 'brain occupies the lower fifth of the brain... developed with the evolution of mammals. corresponds to the brain of the most mammals, and especially the earlier ones.As a brain 'system,' the mammalian brain consists of a series of brain structures around the brainstem which contains the R-Complex. The 'hypothalamus' is connected to other components of the limbic system- 'hippocampus' (spatial memory), 'amygdala' (association), 'mammillary body', 'anterior thalamus', 'cingulate cortex'. Together they form a cap or 'limbus' (Latin for shell or girdle , 'forming a border around' or 'ring') Hence the name 'limbic brain'. The limbic brain, like the R-complex, is concerned primarily with self-preservation and species-preservation and controls the autonomic nervous system. The limbic system functions in primal activities related to defense ('fight or flight' fear response), food and sex as well as activities related to the expression of emotions and feelings (fear and protection) including emotions related to the attachment and care of offspring. These become increasingly complex with interaction of the limbic system... interacts with the thinking part of the brain - the 'cerebral cortex'.
As a brain 'system,' it consists of a series of brain structures - hippocampus which functions in spatial memory, amygdala which functions in the association of events with emotion, mammilary body, anterior thalamus, cingulate cortex and hypothalamus. Together these form a cap or 'limbus' (Latin for 'ring' or 'forming a border around') around the brainstem which contains the R-Complex. Like the reptilian brain, the limbic brain is concerned primarily with self- and species-preservation. With all its parts connected to the hypothalamus, it has extensive influence on human behavior. primary seat of emotions of fear, joy, rage, pleasure and pain, attention, and affective (emotion-charged) memories... salience... what gets your attention; unpredictability, and creative behaviour. and instincts, feeding, fighting, fleeing, and sexual behaviour. It has vast interconnections with the neocortex, so that brain functions are mixture of both. Protective and loving feelings become increasingly complex when the limbic system interacts with the thinking part of the brain - cerebral cortex, neocortex or 'neomammalian brain'. Of particular significance is the role of the limbic system in sense perception and retention of learning or 'memory'. It monitors sensory input, converting it into appropriate modes for processing and directs it to the appropriate memory storage system. Neurochemicals in the limbic system are instrumental in the transfer of memory from short-term to long-term storage which takes thirty seconds...
Cerebral cortex or 'neo-cortex' or cerebrum: superior or rational neo-mammalian brain The third layer which occupies five sixths of the brain is known the 'neomammalian brain', 'neopallium', the 'neocortex' or the 'cerebral cortex'. The cerebral cortex is the latest evolutionary development of the brain... the distinctively primate and human layer... "the mother of invention and father of abstract thought". The cerebral cortex is involved with most mental activity, including spatial and mathematical thinking, meditating, dreaming, remembering, processing and decoding of sensory information. The cortex is two millimeters in thickness and covers the two 'cerebral hemispheres'. The numerous morphological subdivisions are based on the numerous neurological functions - seat of language, speech, thought and sensory processing ... information processing or 'thinking'... motor-control and associations. Sensory-receiving areas and motor-control areas are well-defined. Areas involved with associative events are less well-defined.These include motor-control and some associative events. Sensory-receiving areas and motor-control areas are well-defined. Areas involved with associative events are less well-defined. The cerebral cortex is considered to be the structural and functional 'interface' between input of environmental stimuli and brain output. The cortex is divided into left and right hemispheres...left and right brain. The left hemisphere linear, rational, and verbal and controls the right side of the body. The right hemisphere spatial, abstract, musical and artistic controls the left side of the body.
The interaction of the three brain layers forms the biological basis for the interaction of concepts, emotions and behaviours which make up the learning process
Implications for education Previous to MacLean's work it was assumed that the neocortex dominates the limbic and the reptilian brains.This assumption is anulled by the finding that the mental functions of the neo-cortex can be hijacked by the functions of the other two brain layers. The result is a new working model or 'paradigm' with regards to the study of human behaviour and the learning process.
Although each layer has a separate function, all three layers interact. The interaction of the three brain layers forms the biological basis for the interaction of concepts, emotions and behaviours which together constitute the natural learning process i.e. 'brain-based learning'. In the new paradigm... holistic brain functioning is the basis for education of the person as a whole or 'holistic education'.
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"The brain is best understood in terms of three functioning units: alertness, information processing, and action". (Restak The Brain)
It is interesting that many esoteric spiritual traditions... one brain for the spirit, one for the soul, and one for the body... chakras points along the body or the spine corresponding to nodes of consciousness, related in an ascending manner, from gross to subtle.
references:
MacLean, Paul The Triune Brain in Evolution: Role in Paleocerebral Functions.
The Triune Brain
| Archipallium brain (reptilian brain) Palleomammalian brain (limbic system) Neopallium brain (neocortex) |
each representing a distinct evolutionary stratum that has formed upon the older layer before it, like an archaeological site He refers to these three brains as the neocortex or neo-mammalian brain, the limbic or paleo-mammalian system, and the reptilian brain, the brainstem and cerebellum
influential paradigm forced a rethink of how the brain functions.
It is interesting that many esoteric spiritual traditions taught the same idea of three planes of consciousness and even three different brains. Gurdjieff for example referred to Man as a "three-brained being". There was one brain for the spirit, one for the soul, and one for the body. Similar ideas can be found in Kabbalah, in Platonism, and elsewhere, with the association spirit - head (the actual brain), soul - heart, and body in the belly. Here we enter also upon the chakra paradigm - the idea that points along the body or the spine correspond to nodes of consciousness, related in an ascending manner, from gross to subtle.
The Reptilian Brain.
The archipallium or primitive (reptilian) brain, or "Basal Brian" "R-complex", includes the brain stem and the cerebellum, is the oldest brain. It consists of the structures of the brain stem - medulla, pons, cerebellum, mesencephalon, the oldest basal nuclei - the globus pallidus and the olfactory bulbs. It is rigid, obsessive, compulsive, ritualistic and paranoid, it is "filled with ancestral memories". It keeps repeating the same behaviours over and over again, never learning from past mistakes This brain controls muscles, balance and autonomic functions, such as breathing and heartbeat. This part of the brain is active, even in deep sleep.The Limbic System (Paleomammalian brain)
. In 1952 MacLean first coined the name "limbic system" for the middle part of the brain. paleopallium or intermediate (old mammalian) brain. The old mammalian brain residing in the limbic system is concerned with emotions and instincts, feeding, fighting, fleeing, and sexual behaviour.No emotion has been found to reside in one place for very long. But the Limbic system as a whole appears to be the primary seat of emotion, attention, and affective (emotion-charged) memories. Physiologically, it includes the the hypothalamus, hippocampus, and amygdala. It helps determine valence (e.g., whether you feel positive or negative toward something, and salience (e.g., what gets your attention); unpredictability, and creative behaviour. It has vast interconnections with the neocortex, so that brain functions are not either purely limbic or purely cortical but a mixture of both.
The Neocortex, cerebrum, the cortex neopallium superior or rational (neomammalian) brain, comprises almost the whole of the hemispheres (made up of a more recent type of cortex, called neocortex) and some subcortical neuronal groups two thirds of the total brain mass.
The cortex is divided into left and right hemispheres. The left half of the cortex controls the right side of the body and the right side of the brain the left side of the body. Also, the right brain is more spatial, abstract, musical and artistic, while the left brain more linear, rational, and verbal.