Three Brains in One: Three Layered Brain 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', second the mammmalian brain or 'limbic system', and third the neo-mammalian brain or 'neocortex'. Each has a separate function and depending on the circumstances each can become dominant.  All three layers interact in the processing of information…  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...  

implications for education...

      Evolutionary Development of the Brain: In the 1960s evolutionary neuroanatomist Dr. Paul MacLean, director of the Laboratory of Brain Evolution and Behaviour Behaviour of the National Institute of Mental Health in Maryland, was originally interested in philosophy and 'converted'  to the study of science and medecine while taking a course in the philosophy of science. He 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. He studied the evolutionary development of the nervous system and described the human brain in terms of a three part concentric layered structure or 'triune brain’. Each of the three layers represents a distinct evolutionary stratum that has formed on top of the older layer formed before it. The oldest layer is the reptilian system or 'R-complex'; the second oldest is the paleomamalian stratum or 'limbic system'; the most recent is the neomammalian stratum or 'neocortex'. Each operates as its own brain system with distinct capacities functions for perceiving and responding to the environment. Although each layer has a separate function there are nerve connections between the three layers or ‘brains’ so they interact… are interconnected and interrelated.

       Reptilian brain or system or ‘R-complex’ is the oldest brain and makes up the entire brain mass in reptiles. Also known as the ‘primitive brain’, 'basal brian', 'archipallium', 'root brain' the R-complex consists of structures of the brain stem such as the medulla, pons, cerebellum, mesencephalon, the oldest basal nuclei - the globus pallidus, olfactory bulbs and basal ganglia, the reticular activating system and the midbrain. The functioning of the R-complex is activated when the organism perceives threat and the needs for survival and safety predominte. Functions of the R-complex are related to physical survival and autonomic functions associated with body maintenance…  digestion, reproduction, circulation, breathing, heartbeat, stress response, muscle control, balance also instinctive behaviour patterns of self-preservation… automatic 'primitive' behaviours associated with territoriality, ritualism, paranoia, social dominance, status maintenance aggression, tendency to follow precedent, awe for authority, social pecking order behaviour, compulsiveness, deception, prejudice and resistance to change. When the R-complex dominates the person becomes rigid, obsessive, compulsive, repetitive behaviour, does not learn from experience. This part of the brain is active, even in deep sleep

     Mammalian brain or 'limbic system' The second layer... middle part of the brain occupies the lower fifth of the brain...  'palleo-mammalian brain'...'limbic brain. the paleopallium or intermediate (old mammalian) brain... developed with the evolution of mammals. The 'mammalian brain' corresponds to the brain of most mammals, and especially the earlier ones. The mammalian brain is a brain 'system' which 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 to which all the other parts are connected.. Together they form a cap or 'limbus' (Latin for shell or girdle 'ring' , 'forming a border around' or 'ring')  around the brainstem which contains the R-Complex.  With all its parts connected to the hypothalamus, it has extensive influence on human behavior. The limbic brain, like the R-complex, is concerned primarily with self-preservation, species-preservation and controls the autonomic nervous system. functions in primal activities related to defense ('fight or flight' fear response),  is concerned with emotions and instincts, feeding, fighting, fleeing, freezing sexual behaviour.   primary seat of emotions and feelings of fear, joy, rage, pleasure and pain, attention, protection and affective (emotion-charged) memories…. determines valence positive or negative feeling and salience...  what gets your attention; unpredictability, and creative behaviour.  and instincts, feeding, fighting, fleeing, and sexual behaviour...  activities related to the expression including emotions related to the attachment...protective and loving feelings and care of offspring. These become increasingly complex with interaction of the limbic system with the thinking part of the brain - the 'cerebral cortex' seat of thought and voluntary movement.. It has vast interconnections with the neocortex, so that brain functions are mixture of both.   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: The third layer 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. superior or rational is two millimeters in thickness and covers the two 'cerebral hemispheres'occupies five sixths of the brain (two thirds of the total brain mass) comprises almost the whole of the hemispheres and some subcortical neuronal groups…  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 cerebral cortex is involved with most mental activity, invention and abstract thought including spatial and mathematical thinking, meditating, dreaming, remembering, processing and decoding of sensory information..  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.  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.  

Integration and coordination between the three brains is inadequate, a genetic problem in our species...  This has implications for human development.

Implications for education  Previous to MacLean's work  it was assumed that the neocortex dominates the limbic and the reptilian brains.This assumption is discredited by the finding that the mental functions of the neo-cortex can be hijacked by the functions of the other two brain layers.

The interaction of the three brain layers forms the biological basis for the interaction of concepts, emotions and behaviours which together make up the natural learning process or ‘brain-based learning'..

 The result is a new working model or 'paradigm' with regards to the study of human behaviour and the learning process In the new paradigm...  holistic brain functioning is the basis for education of the person as a whole or 'holistic education'. 

Education for optimal human development is required for our species survival.

 References: MacLean, Paul The Triune Brain in Evolution: Role in Paleocerebral Function

 Notes: 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 (neocortex) one for the soul (limbic), and one for the body (reptilian).  Similar ideas can be found in Kabbalah, in Platonism, and elsewhere,  chakras points along the spine correspond to nodes of consciousness, related in an ascending manner, from gross to subtle.