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Bits of Neurology for Philosophers


1 Remarks about Intelligent Design.
2 Temporal-limbic versus fontal lobe spirituality.
3 The mammalian brain, the democratic neuron and philogenesis.
4 Major brain structures and their functions.
5 The triune brain : reptilian, mammalian and human.


1 Remarks about Intelligent Design.


Dembski & Behe (1998) and Hamilton (2002) argue the universe shows intelligent design. Central to the debate is the question whether the organization of the universe in general and the emergence of life in particular is a matter of accident ? Hoyle (1986) concludes random events and change occurrences are insufficient to account for the complexity of living organisms. Earlier, Prigogine (1979) saw the return of finality in open, dissipative systems.

Instead of blind chance, the universe shows "finality". This "causa finalis" of old (cf. Aristotles, Metaphysics, Book 1) is reformulated as the "anthropic principle", stating that if any of the physical constants were to vary from the fine-tuned values we determined, life would not be possible. Its "weak" version reasons certain cosmological features are conductive to a universe tuned to life, whereas the "strong" version holds the universe to be bound to produce conscious and intelligent beings. This strong "tuning" suggests a Great Architect, a principle ordering the parameters of the universe and its life. Every slight variation in the known natural constants, drastically alters the organization of the universe. Of all possible universes (cf. Leibniz), ours allows for life and consciousness. The universe was meant to be conscious and humanity allows it to be so. These arguments are studied in more detail in Does the Divine exist ?, 2005.

In biology, neo-Darwinism is also challenged. Indeed, the notion of "variation" as "random mutation" is consistent with the denial of purposeful design, making natural patterns without inherent plan (Monod, 1970). Recently, a progressive metamorphosis, with the emergence of increasingly complex and intelligent species in a step-wise, sequential pattern was proposed (Joseph, 2002). Indeed, large-scale protein innovation (Aravind, 2001), so-called "silent genes" (Henikoff, 1986, Watson, 1992), the precise regulatory control of genome novelty (Courseaux & Nahon, 2001) and the overall genetically predetermined "molecular clockwise" fashion of the unfoldment of the human being (Denton, 1998), etc. underline the evolutionary metamorphosis theory of life and intelligent design (weak anthropic principle).

According to Darwin's evolutionary theory, phenotypic variation originates from random mutations independent of any outside selective pressure.

"However, recent findings suggest organisms have evolved mechanisms to influence the timing or genomic location of heritable variability. Hypervariable contingency loci and epigenetic switches increase the variability of specific phenotypes ; error-prone DNA replicases produce bursts of variability in times of stress. Interestingly, these mechanisms seem to tune the variability of a given phenotype to match the variability of the acting selective pressure. Although these observations do not undermine Darwin’s theory, they suggest that selection and variability are less independent than once thought."
Rando, O.J. & Verstrepen, K.J. : "Timescales of Genetic and Epigenetic Inheritance", in Cell, vol 128, 655-668, 23, 2007, my italics.

Intelligent design calls for a Designer, conceptualized as :

  • a "pneuma" or "subtle" matter (cf. Stoic cosmology) = pantheism ;

  • a transcendent principle or Supreme Being = theism ;

  • both transcendent & immanent, in the world but not of the world = pan-en-theism ;

  • nondual, ineffable, nameless, absolute = apophatism.

Pantheism is difficult to maintain, for the characteristics of the Designer are so different from those of the design itself. It downgrades the Designer (reduced to a "subtle" kind of matter or "pneuma") and so harms the principle of intelligent design itself. Nevertheless, pantheism is the most intelligent option in an immanent metaphysics, positing the Divine insofar as it is immanent and constantly present everywhere in the world (cf. the argument of conservation).

Theism is a consequent view on the Designer (supposed to be radically different from the design itself), but then it become difficult to understand how the design can come into being if its Designer is so far removed from the design. A solution through mediation (a "Pharaoh", a "Buddha", a "Christ") mystifies the nature of the mediator and cancels the procedure, for nobody understands how the Designer designes the mediator, except dogmatically. The notion everything is part of the Designer (cf. Qabalah, were creation happens in a space vacated by God), is a stronger position, although the conceptualization of the Designer remains paradoxical (but this does not affect the design). How can what is "far" (transcendent) simultaneously be "near" (cf. Porete's "Loing-Près") ? The paradoxical bi-polarity of the Divine, the theonomy of perplexity of the mystics is however in accord with this position. Furthermore, transcendent metaphysics always exceeds its limitations, as nondual thought is not conceptual but of the nature of direct discovery and realization (cf. Intelligent Wisdom, 2007).

Pan-en-theism, as in Qabalah, seeks to find the "traces" of the Designer in the design. These enable us to remodel (perfect) parts of the design in the light of what is known about how the Designer designed the design. The latter is an integral part of the Designer, not some entity "outside". The Designer has no "outside", for the unlimited has no borders. The design is positive (full) existence within the negative (empty) being of the Designer, although this "emptiness" is rather a potential, virtual reality or set of all possibilities than an absolute absence of anything (an enduring nothingness).

Separated from the universe, there is virtuality, potentiality and possibility, which is more than non-entity. That something is the "prima materia" or transcendent source of being. This negative, virtual existence of the Designer is Designer consciousness (i.e. awareness untained by matter or information). Designer consciousness (the absolute in its absoluteness) creates an intelligent design, i.e. a finality expressing the eschatological activity of the Designer. This happens by confining a spark of this sheer intentional, preexistent Being within certain limits. This allows for organization, composed of consciousness, information and matter. This virtual, preexistent, ineffable, primordial, pre-creational, limitless, infinite Being contracts the manifestation of the design within the sphere of its own set of "natural" la
ws. As before creation nothing is manifest, the Designer is immaterial. As before creation no differentiations exists, the Designer is not informational (the names of the absolute are part of the design, not the Designer). This creativity is exclusively intentional and untouched by, unmingled with, veiled from the processes of involution & evolution.

Only such preexistent, pristine consciousness is able to create its own intentional objects, to wit : the design of universes, operated by consciousness, information and matter. As the consciousness at work within a universe is always limitated by its co-relative bond with information and matter, i.e. the operant code of existence ruling the logical confines of this universe and its physical conditions (spatiotemporal, dynamical, atomic), only the Designer is deemed to be absolutely free.

  • involution : generation : materialization of consciousness ;

  • evolution : liberation : spiritualization of matter.

Generation initiates a universe ("exidus"). With the manifestation of life, consciousness eventuates and the return-sequence is initiated ("reditus"). This evolutionary sequence (matter, information, consciousness) initiates the progressive metamorphosis, step-wise producing increasingly complexer creatures, able to manifest, execute & compute more meaningful intentional states. Both sequences are dynamical, fluent, creative & intelligent. With the emergence of the human brain, the ability to materialize consciousness dramatically altered the natural sequence of events on this planet, showing that the intentional world is indeed the realm of freedom. 

In this ontological speculation, the Designer is present in the fundamental intelligence of the material design ("arché") and the meaningful complexification of its elements ("telos") of our universe. This is the text, script, scenario (information) the Designer devised. This "presence" of the Designer as "law" rules the manifestation of consciousness and the spiritualization of matter. From a metaphysical perspective, science is then the discovery of the abstract trace of the Designer in the design.

So in Western creational ontology, the process of involution/evolution, the life-span of this world, is able to run its course and complete itself as a result of three fundamental eschatological impulses :

  • material impulse : the Designer as "Creator" fashions a material matrix as an object within the limitless full-emptiness of pre-creation (cf. the "Nun" in Ancient Egypt or "Ain Soph" and "tzimtzum" in Qabalah). An infinite being, a pure act (or unmoved mover - cf. Aristotle) restricts itself to create a real but finite being. This material matrix, or "hardware" of our universe, is a unity of chemical elements (especially helium, hydrogen), a host of elemental particles (like the photon), as well as a series of physical forces (superforce, weak, strong, gravity, electro-magnetism) and their differences (or energy, conceived as the product of differences). For Hegel, the formidable extention of the physical universe speaks of the intensity of the non-spatial spirit (or the names, signs, traces, residuals, "reshimu" of the Designer present in the design) ;

  • informational impulse : the Designer as "Great Architect", organizes the material matrix through physical constants and intelligent laws reducing all possible cosmoi (all variations of the components of the matrix) to our present, observable universe, with its characteristic universal laws of physics, open windows to the emergence of life. Fundamental is the universal repetitive cycle of expansion and contraction of all matter within this universe and maybe between universes (waning & waxing forever). Code is added to the material matrix, allowing for the formation of DNA, the informational building block of life and storehouse of cellular intelligence, memory, planning skills & language. The vital principle holds : our universe is built to eventually produce the evolution of living beings gifted with intelligence, or the "software" of this universe ;

  • consciousness impulse : the Designer as "Great Artist", replicates in miniature the proto-type of the universe (macrocosmos) as an "Ultimate Concern" (cf. Tillich, 1952) or primordial example aspired to by creatures (microcosmos) able and invited (not forced) to follow the "straight path" (the convenant between humanity and the Designer). Hopefully this leads to a perfected seering and meaning capacity in this universe (cf. "Omega" in Teilhard de Chardin, 1959, or nondual thought - cf. Intelligent Wisdom, 2007). In doing so, the universe changes for the sake of the endless meaning-complexification arrived at by highly complex beings such as humans. The anthropic principle holds : the material and informational processes of the universe have parameters which favour the emergence of hominoids (pre-hominids) and hominids. They have brains able to process (compute, transmit, mediate) consciousness and volition, or the "userware" of this universe.

Four analogies provide a strong backing for the case or premiss presenting the non-spontaneous becoming of the actual world process. How to detect non-spontaneous "design" ?

  1. design by analogy of human products : the proximate cause proportional to the order, harmony, fitness & freedom observed in the world can be identified (named) by following the analogy of products of human design. In doing so, only the "form" aspect of the world is observed to identify design. In this way, the "matter", or substance of the world, is not targeted, and it is no longer necessary to prove in addition, that the things of the world, given the laws of nature, were in themselves incapable of such order and harmony. Hence, to avoid backing the premiss, it is accepted that no supreme intelligence exists in the material substance of the things of the world. In the traditional Peripatetic account, four causes are at work in the world : material, efficient, formal & final. By analogy of human products, the design involves the formal and final causes only ;

  2. design by analogy of outcomes in living organisms : all living things seem tailor-made for their function and appear to interact purpose-fully with their environments : animals use camouflage, most parts of our bodies, down to our DNA helix, are very delicately engineered, and large numbers of apparent coincidences exist between various living organisms, etc. These highly ordered biological schemata seem places of reference to back the premiss, for how could such a complexity rise out of simplicity without a pattern of intelligent choices ? The chances are small enough, given what science demands in other areas, to dismiss spontaneous, random activity. Nevertheless, this study of outcomes was seriously affected by the discovery of the Darwinian principle making organisms evolve by natural selection, adaptations and (random) mutations. If all biological events can be explained by this principle (turned into a paradigm), then indeed there is no "purpose" behind the grand natural symphony. Darwin (1809 - 1882) and neo-Darwinism were able to explain much of the data of his time and the first half of the previous century. Even societies could be studied in terms of the survival of the fittest (Monod, 1970). But, recent studies show how the theory has been unable to account for certain more subtle phenomena uncovered by the biochemistry of the last 50 years, mostly related to complex events such as protein transport, blood clotting, closed circular DNA, electron transport, photosynthesis etc. So, beyond the grip of Darwin's macroscopic view, on those more subtle levels of biology and biochemistry, design may be detected and purposeful arrangement of parts suspected. A revised analogy of subtle outcomes becomes thus again possible, leading to a more comprehensive backing of the premiss ;

  3. design by analogy of the forms of the laws of nature : Maxwell (1831 - 1879) pointed to molecules as entities not subject to selection, adaptation & mutation. The contrast between the evolution of species, featuring biological changeability, and the existence of identical building blocks for all observed actual physical entities is crucial. Calculate the odds of spontaneous emergence, given the effectiveness of Newton's laws on the mesolevel (the inverse-square law of gravity being optimal for the becoming of the Solar system), our knowledge of what happens in stars (in particular the production of carbon and oxygen) and the cosmology of the Big Bang. A choice has to be made between either an intelligent design (which does not offend except the ill informed) or a monstrous random and blind sequence of accidents producing a gigantic complexity, in other words either a natural higher intelligence or the ongoing mathematical miracles of a blind nature morte. Indeed, ad contrario, the form of the laws of nature underlines the presence of a deep-laid scheme, representing an accurate mathematical descriptions of the natural order (both in genesis as in effect). Although no "consensus omnium" has been reached, the laws of nature likely accommodate biology ;

  4. design by analogy of fundamental constants : the actual irreducible mathematical presence of immutable natural building blocks such as the natural constants, gives a palpable proof of the existence of something independent of every human measurement (and its biological constitutive). These constants define the fabric of physical reality and determine the nature of light, electricity and gravity. They make particles come into existence and fundamental forces work. They actualize the laws of physics by giving equations numerical quantity and are necessary in the logic of physics. What can be said about the particular values takes by these constants ? The conditions for order and eventually life to develop have been found to heavily depend upon these constants. Indeed, although mathematically, the equations of physics, representing the fundamental architecture of the order of the world, also produce outcomes when other quantities of the same constants are put in, the world would be lifeless and barren (instead of a haven for incredible complexity) if even a small amount of these values would be changed. Ergo, the various values of the constants of nature were designed, and pre-planned. An infinite number of different worlds are possible, but only in one are order, fitness, beauty and life actual. Only our universe has observers witnessing it.

Instead of blind chance, the universe has "finality", i.e. an ultimate aim or purpose. This "causa finalis" is the notion backing the "anthropic principle". For if any of the natural constants were to vary from the fine-tuned values physics determined, life as we know it would not be possible. This "weak" anthropic principle posits cosmological features conductive to a universe tuned to and generative of life as we know it. Accepting life is bound to be observed, the "strong" principle affirms the universe is bound to produce conscious and intelligent beings. This addition of the observer or witness is a demand of quantum theory. The observer is thus always part of the experiment. The strong version argues for an immanent Architect of the world (explaining the unity of the world).

  • weak anthropic principle : the fabric of the world is conductive to life ;

  • strong anthropic principle : the fabric of the world is conductive to the observation of life and the continuum of all observations imply an immanent Witness of all possible forms of life.

The order of the world proposed by science is no longer Newtonian, although most equations of relativity can be made "classical" by eliminating the Lorenz-contractions accompanying high speeds. To solve the equations covering most practical matters at the mesolevel of the macroscopic, the Euclidian and Newtonian notions about reality are adequate. But deep down, at the microlevel of physical reality, in the vast so-called empty spaces between electron and atom core and within the core itself, potentialities and propensities exist which are ruled by a different set of laws.

Besides the strange logic at work in classical quantum mechanics, the more "revolutionary" zero-point physics, or
free energy physics (Puthoff, 1989), understands the vacuum of space as a "plenum", i.e. a fullness of energetic potentialities in balance. This equilibrium prevents the enormous energy potentials from becoming actual, which therefore appears as a void or a vacuum. But every point in empty space, is a locus of convergence of humongous energies, coming from all directions simultaneously, balancing them out. At any point where there is an imbalance or asymmetry in this omnidirectional canceling of energies, there appears a disturbance known as matter. All particles of quantum physics are various modes of asymmetry of the zero-point field of the vacuum with itself. This zero-point energy is seen as the result of the unpredictable random fluctuations, which, in classical theory, are all zero. But, even at a temperature of absolute zero, where no thermal agitation can have effects, the flux remains.


2 Temporal-limbic versus fontal lobe spirituality.


Let us consider these landmarks :

  • ca.18 billion years ago : "Big Bang", beginning of the observable universe ;

  • ca.5 billion years ago : formation of our Sun ;

  • ca.4.6 billion years ago : the formation of the Earth ;

  • ca.3.5 billion years ago : Sun-worshipping single-celled organisms ;

  • ca.3 billion years ago : the ability to exchange information between members of the animal kingdom ;

  • ca.1 billion years ago : sex becomes a widespread form of reproduction in oxygen-breathing, multicellular creatures ;

  • ca.700 million years ago : creation of the first neuron (one without axons and dendrites) ;

  • ca.500 million years ago : first primitive aggregates of neural ganglia into lobes ;

  • ca.500 million years ago : start of formation of primitive limbic system ;

  • ca.500 million years ago : first vertebrates swim the ocean and plants invade land ;

  • ca.300 million years ago : first great forests ;

  • ca.100 million years ago : first mammals appear ;

  • ca.30 million years ago : first apes ;

  • ca.5 million years ago : first erect hominids emerge and spread across the face of the planet ;

  • ca.2.5 million years ago : earliest samples of chipped pebbles, the work of Homo habilis ;

  • ca.1.6 million years ago : Homo erectus walks and uses the same stone tools for a million years ;

  • ca.450.000 years ago : limbic system functional in sharks ;

  • ca.500.000 years ago : brain of hominids doubled in size ;

  • ca.500.000 years ago : emergence of the Homo sapiens neanderthalensis ;

  • ca.100.000 - 40.000 years ago : the Cro-Magnon brain is formed (Homo Sapiens sapiens) ;

  • ca.40.000 - 10.000 years ago : the human brain eventuates ;

  • ca.10.000 BCE : start of the Neolithic and human civilization.

By 30 million years, higher primates had emerged and dwelled in Africa, China and India. From these wide ranging hominoid stocks, a variety of hominoid pre-hominids began to evolve : Dryopithecus, Sivapithecus, Ramapithecus, Ankarapithecus, Ouranopithecus, Giganotopithecus, etc ... These protohuman types experienced the end of the receding forests and the expansion of the savanna & grassland. As a result, around 5 mllion years ago, some hominoids began to increasingly live upon the ground. 

"... our feet and legs are the most human things about us and are ultimately answerable for what happened late in our evolution. For one thing, standing erect on our legs freed out hands from any work in moving us about."
Howells, 1997, p.55.

Living on the ground caused further evolutionary metamorphosis and gave rise to the first hominids, such as Australopithecus Afarensis (Joseph, 2002), who's erectness is clear (Howells, 1997, p.81). A wide range of Australopithecus emerged 5 million years ago, throughout Africa as well as China and Java. Around 2 to 3 million years ago, Australopithecus was joinded by the Homo habilis ("able with hands") of which several varieties appeared in Africa, China and Indonesia (Howells, 1997, pp.93-120). Austrolopithecus and Homo habilis continued to evolve giving rise to a wide variety of species, collectively referred to as the Homo erectus, who appeared ca.1.6 million years ago. A critical brain expansion had happened :

  • Australopithecus : 450 - 520 cc, who roughly had our teeth and feet ;

  • Homo habilis :  600 - 800 cc, who made simple stone tools ;

  • Homo erectus : 900 - 1000 cc, larger brain and a skeleton like our own ;

  • Homo Neanderthalensis : 1.033 - 1.681 cc, larger brain but frontal lobes less developed ;

  • Homo Sapiens sapiens (Cro-Magnon) : 1.600 - 1.681 cc, large brain with developed frontal lobe ;

  • Homo Sapiens sapiens (present-day humans) : ca. 1450 cc.

"It must be more than a coincidence that tools and the early Homo appeared at the same time. Brains continued to expand, and tools continued to become more varied and better defined."
Howells, 1997, p.100.

With the Homo erectus the brain gradually doubled in size. He emerged in Asia, Africa and Europe. Homo erectus harnassed fire (to keep warm, to provide light and to cook their food), developed crude shelters and home bases and utilized earth pigments (Joseph, 2002, p.118). But in a million years he never changed his tools ... 

Archaic Homo sapiens neanderthalensis (or Neanderthals) first emerged almost 500.000 years ago. Until 300.000 BCE, Homo erectus continued to dominate parts of the planet, and so Neanderthals and Homo erectus shared the planet in different geological locations for almost 200.000 years. Ca.100.000 BCE, the Homo sapiens sapiens (Cro-Magnon) appeared in North and South Africa and between 50.000 and 40.000 BCE, they spread upward into the Middle and Far East, then into Europe, China, the Americas and Australia (Joseph, 1993, p.29). With them, we've reached our true ancestors.

"... let us be warned that the Upper Paleolithic Europeans have no copyright on the apparent 'sapiens explosion'. It would appear instead that the European Upper Paleolithic was more a ripening expression of the new human level, no a cause of it, and we need much more evidence on the nature of this florescence."
Howells, 1997, p.185.

Different species of hominids
were living in different parts of the world simultaneously : 

  • Homo erectus : flourished from 1.6 million years until 27.000 BCE (Java) ;

  • Homo sapiens neanderthalensis : from 500.000 until 29.000 BCE ;

  • Homo Sapiens sapiens : from 100.000 until 10.000 BCE.

"Hence, similar to the step-wise worldwide pattern of multi-regional, multi-phylectic metamorphosis which has characterized the progressive emergence and increased complexity of plants and animals, the available evidence suggests that human 'evolution' has unfolded multi-regionally in a step-wise, progressive fashion, with some groups lagging far behind and others being left behind altogether and becoming extinct."
Joseph, 2002, p.121.  

The differences between Homo sapiens neanderthalensis (culminating in the Middle Paleolithic, i.e. between 150.000 and 35.000 BCE) and Cro-Magnon Homo sapiens sapiens (
of the Upper Paleolithic, i.e. between 35.000 and 10.000 BCE) reveal a major point of interest for neurospirituality (Joseph, 1999, 2002). Neantherthals had a sloped and stunted frontal cranium, whereas the Cro-Magnon had a brain larger than that of the average contemporary human being. 

In 1868, during construction for a railroad, in a shallow cave at Cro-Magnon in the Dordogne area of southern France, a number of obviously ancient human skeletons were found. The cave was investigated by the French geologist Louis Lartet, who uncovered five archaeological layers. The human bones found in the topmost layer proved to be between 10.000 and 35.000 years old. Cro-Magnon was robustly built and powerful and is presumed to have been about 166 to 171 cm (about 5 feet 5 inches to 5 feet 7 inches) tall. The features were generally heavy and solid. The forehead was straight, with slight browridges, the skull long and narrow, and the face short and wide. The ape-like features still apparent in the Neanderthals had vanished. 

Let us highlight a few important differences :

  • Homo erectus : this hominid left no physical traces of ritualized behavior. The notion they were the first living creature on Earth able to perceive a spiritual reality, and this because their complex brain contained all the key neuronal structures for creating language -cf. the parietal lobe- (Newberg, d'Aquili & Raus, 2002, p.66) is a controversial idea. Cranial analysis suggests the opposite (cf. infra). In a million years, Homo erectus was unable to invent new tools. They lived in small groups, inhabited caves, and finally mastered fire, enabling them to, as it were, "domesticate" the night and sleep without fear (and invent the waking dream ?) ;

  • Neanderthals : they possessed a developed inferior temporal lobe. Together with the limbic structures within it, these neuronal networks allowed them to execute individual, emotional and religious experiences, including long term emotional attachments and intense love (Gloor, 1997). But with such a brain, they were unable to make complex tools or compute abstract thoughts. They were people of passion. Nevertheless, it seems the experience of Divine Presence was already part of their existence and behavioral patterns, making of the Neanderthals the first hominids with spiritual capacities. Some authors have argued the evidence of this is sparse and controversial. But general agreement exist about the fact that due to their deficient prefrontal cortical development, the Neanderthals -compared to modern humans (Balter, 2002)- lacked symbolic charge. Their tools were "use-specific" and served a unidimensional purpose ;

  • Cro-Magnon : with the increase of the frontal lobe, a "symbolic explosion" (Leroi-Gourhan, 1982) could take place. The Cro-Magnon tool kit consisted of well over 125 items. These "intelligent" humans were the first "intellectual giants", producing artists, musicians, craftsmen, sorcerers (shamans), priests, hunters, fishermen, gatherers & herbalists. Some were city dwellers, others lived in tents made out of animal skins. They had complex mortuary practices. The role of the mother goddess was omnipresent (a practice to continue well into the Neolithic - cf. the great goddess in Predynastic Egypt). She was attended by animals and shamans. They invented initiatoric rites, in which one had to enter the hidden entrance of an underground cave and crawl a considerable distance, through a twisting, narrrowing, pitch black tunnel before reaching an underground cathedral lit with light candles and lamps, with painted animals on its walls. They were the first to use such devices to invoke the experience of death and the subsequent initiation into a new state of consciousness. These superior hominids were able to symbolize their religious experiences, and thus shape religions, spiritual traditions and develop theological notions like heaven, hell, god and goddess, as well as shamanism and priesthood.

Neanderthal and Cro-Magnon
reconstructed by Howells, 1997, p.145.

The distinction between Neanderthal and Cro-Magnon spirituality is on record. From an evolutionary, philogenetical perspective, the human brain emerged two fundamental executant levels to process spiritual experience :

  • a temporal-limbic "root" spirituality, involving a direct, emotional, awe-strikken, passionate, profound spiritual experience and 

  • a prefrontal cortex "symbolic" spirituality, allowing for the computation of artistic, initiatoric, theological and abstract cultural superstructures (mediations, stabilizations) of such experiences.

The Cro-Magnon brain was significantly larger than the Neanderthal brain. The differential evolution of the frontal lobe and angular gyrus is based on the study of tools, hunting technology, artistic and symbolic developent and social organization in the Middle and Upper Paleolithic (Joseph, 1993, chapter 6). Spiritual experiences processed by the inferior temporal lobe, amygdala and hippocampus focus on an individual's profound link with a higher presence : the direct experience of what is spiritually significant. The radical confrontation with radical otherness can not be explained or understood. There is no elaborated symbolic representation at this level of direct, mystical contact. The Neanderthals show it is possible to be very religious but not smart, i.e. unable to "explain" (symbolize) and thus made decontextualized use of what has been experienced. Nevertheless, the hereafter is sensed, as well as the importance of death as a passage (the idea they only buried their dead to deal with odor seems far fetched - Rudavski, 1991). 

"Neurophysiologist Rodney Holmes, looking at the record of archaeology, theorizes that hominids since the Neanderthals have been Homo religiosus - creatures in search of meaning and significance."
Albright & Ashbrook, 2001, p.156.

The spirituality executed by these temporal & limbic wirings deals with the direct experience devoid of abstract thought and symbolizing. Volitional manipulation is not at hand. The software of the "God-spot" runs on the same neuronal structures computing animal emotions and storinge highly individual experiences. Terror, rage, violence, emotional arousal, pleasure, joy, trance, ecstacy and the holy cohabitate ! These amygdalean associations are not taken away with the development of frontal lobes, but integrated in a higher structure, enabling a more symbolized, linguistic and artistic approach of spirituality, inventing rules and codes to "channel" the "basic" Neanderthal sensing of the "real" transmitted by the limbic system.

"Adam, the being created with two hands, is a locus of coincidences of opposites."
Sells, 1994, p.86.

With the emergence of the frontal lobes, a new feature was added to the existing temporal executives. A "pure" frontal lobe spirituality never existed, nor will it. The frontal lobes enabled the hominids to symbolize the experience of the sacred, higher presence (in language), and so an element of manipulation and spiritual craftsmanship entered into the picture together with self-awareness (a conscious division between the experiencing "I" and the object of spirituality, i.e. radical otherness).

Neanderthal and Cro-Magnon craniums
Joseph, 2002, p.349.

Between ca.35.000 - 29.000 BCE, Neanderthals and evolved Cro-Magnon shared the Earth (ca. 10.000 BCE, Cro-Magnon gave way to the Neolithic peoples). Maybe the latter exterminated the former (Joseph, 2002, p.349). The Cro-Magnon's superiority was based on abstract thought, individuality, speech and an enhanced regulation of emotion and action as well as tool-making and the consolidation of cultural forms. In Neanderthal craniums, the importance of visual input and also a less developed frontal lobe stand out. The receding eyes of the Cro-Magnon made room for a frontal development, which was added to the overall development of the cerebrum. If the Neanderthal did not possess an angular gyrus (cf. infra), as made probable by Joseph (2002, pp.313-360), is it then not likely this ancestor had only perfected the skills of the archaic hominids (like Homo erectus) ? His mode of thought was mythical and iconical. Limbic executants are at work and rule the game.

On the one hand, the frontal lobes temper the passions of temporal-limbic spirituality by symbolizing fear and joy, as well as developing vocabularies to give "meaning" to Divine Presence and the holy. On the other hand, too much superstructures or a rejection of religion (as in atheism), may cause the communication between the "old" systems and the "new" cortex to be more unreliable or disrupted, leading to a lower level of integration of the brain. This evolutionary block puts limitations on its executant capabilities (cf. the absence of creativity and inventivity, as well as uplifting, joyous, profound, holy experiences).

The symbolization of the holy experiences computed by the amygdalean-hippocampal "God-spot", gives to their raw directness an opportunity "to leave the limbic system" and recieve a more definitive form. Ex hypothesi and from a neurospiritual point of view, a superstructure is efficient if it does not disrupt or block the feedback from the prefrontal cortex to the limbic "God-spot". In other words, symbolization is inefficient, when it disables the use of the "God-spot" beyond the limbic system, or condemns it to the unconscious, as in atheist ideologies. The experience of Divine Presence has specific neuronal executants and so the mind is called to position these experiences within the conscious field of operation of the first person phenomenology.

In mature mystics, the profound & symbolized experience of the holy is continuous, implying an efficient frontal lobe/temporal-limbic integration. The "God-spot" executes the direct experience of the Divine and the "God-circuit" lets it run through the neocortex, especially its prefrontal area and back to the limbic system. During the frontal lobe phase, volition becomes associated (cf. the impact of spiritual experiences on individual morality). The overall efficiency of this circuit is, ex hypothesi, part of the evolutionary purpose of the brain as a potentially highly complex but integrated organ, executing a variety of mental states, making the essential peace possible between, as it were, the limbic Neanderthaler and the frontal Cro-Magnon. The brain may also compute the bi-polar nature of all spiritual experience, rooted in the basal telencephalon (hippocampus, amygdala) and the limbic system (thalamus, hippothalamus), but branching out towards the neocortex, and thus enabling the expression of higher order spirituality, based on self-experience and symbolization.

Neanderthals & Cro-Magnons show the root of human spirituality to be buried in high-order, lower mammalian structures covered with low-order, higher cortical networks.


3 The mammalian brain, the democratic neuron and philogenesis.


A comprehensive description of the human brain lies outside the scope of this text and the reader is referred to Bear, Connors & Paradiso (2001) and other similar studies. Let me sketch an outline and focus on those details which are of importance in our philosophical investigation of the neuronal executants of spiritual experience. Indeed, the human brain is the most complex piece of matter on Earth. The description below is thus but a scaffold of some of its important contents & functions.

general characteristics


The human brain is the most complex organ known in the observable universe. It expends 25% of our energy intake, while consisting in only 2% of our tissue mass. In general, at any given moment, 1 to 10% of all our neurons fire, on average 100 times a second. If processing speed is measured in "FLOPS" ("floating point operations per seconds" or the number of calculations with a floating point done in one second), and each firing is one FLOP, then 1 teraflops is the upper limit of the brain's information processing speed (1 megaflop = 1 million FLOPS, 1 gigaflop = 1000 megaflops, 1 teraflops = 1000 gigaflops). Counting in the synapses brings the estimated speed up to 10 teraflops (Moravec, 1988). 

The first creatures to possess one single neuron, the first cellular brains, were able to process, store and express a billion times more information than any sensory or motor cell could (Joseph, 1993, p.13). Living beings such as bacteria, algae, mosses, fungi and plants have no brains, although they are able to communicate & interact. Sponges have nervelike tissue, concentrated around the external orifices and pores. In the nervenet of a worm, we already recognize two large pairs of clusters of similarly functioning neurons (neural ganglia) in the head region. Neurons are able to plan and create memories as communicate this to other neurons in the form of electrical and chemical messages. 

The human nervous system follows the basic mammalian plan, although -due to its extreme complexity- it is distorted as a result of the selective growth of some parts, like the human neocortex. The nervous system of all mammals has two divisions : the central nervous system (CNS, encased in bone : brain and spinal cord) and the peripheral nervous system (PNS). The latter encompasses all parts of the nervous system other than the brain and the spinal cord. Recently, neurocardiology and neurogastroenterology discovered two other neuronal ganglia, respectively situated in the heart (and Solar Plexus) and in the gut area.

In 1991, after years of extensive research, dr.J.Andrew Amour of Dalhouse University in Halifax, Canada, evidenced the existence of a functional "heart brain". This is an intricate network of neurons, neurotransmitters, proteins and support cells allowing activity independent from the "head brain". Many of the signals flowing out of the heart to the brain regulate signals flowing out of the brain to the heart, the blood vessels, glands and organs. The work of the Laceys (1970) and others made clear neural messages from the heart affect cortical activity, including the amygdala and the higher brain centers.

There are at least forty thousand neurons in the heart. This is as many as in the various subcortical areas of the brain. The heart is not merely pumping blood, but demonstrating a complex set of interactions between these neurons and those in the brain. The idea peripheral autonomic ganglia function as "little brains" dates from the XVIIIth century, and was formulated by Benigne Winslow, a Swedish anatomist working in Paris. These neuronal networks were considered to perform routine tasks required to maintain organ function, ensuring afferent data arising from each organ did not flood the spinal cord and the brain.

"Only one or two thousand nerve fibers connect the brain to the hundred million nerve cells in the small intestine. Those hundred million nerve cells are quite capable of carrying on nicely, even when every one of their connections with the brain is severed ..."
Gershon, M. : The Second Brain, HarperCollins - San Francisco, 1999, p.xiv.

When describing the "wiring" or axons of the nervous system, two important terms should be kept in mind : afferent ("carry to") and efferent ("carry from"). Axons transporting information from the PNS to the CNS are afferents or sensoric axons (incoming data). Those emerging from the CNS to innervate the muscles or glands are efferents or motoric axons (outgoing (re)actions).

Mammalian Brain
Central Nervous
System (CNS)
Peripheral Nervous
System (PNS)
brain voluntary, somatic
spinal cord autonomic, visceral

The PNS is divided in two parts : the voluntary, somatic PNS and the autonomic nervous system (ANS). The former contains spinal nerves innervating the skin, the joints and the muscles. The latter consists of neurons innervating the internal organs, blood vessels and glands (it is therefore also called the visceral PNS). 

Looking down on the nervous system, we see it can be divided into two equal halves, the right side of the brain and spinal cord being the mirror image of the left side. This bilateral symmetry is valid for most structures within the nervous system, which come in pairs along the midline (as can already be seen in worms).

A side (lateral) view of the mammalian brain reveals four parts are common to all mammals :

  • the cerebrum ("brain") : is the anterior (rostral-most) and largest part of the brain - a top (dorsal) view reveals a split down the middle into two cerebral hemispheres (separated by the sagittal fissure) - in general, the left (right) hemisphere receives sensations from the right (left) side of the body - a thin sheet of neurons, the cerebral cortex ("bark"), lies just under the surface of the cerebrum ;

  • the cerebellum ("little brain") : although dwarfed, in humans it contains as many neurons as the whole cerebrum and is a movement control center with extensive connections with the cerebrum and the spinal cord - in general, the right (left) cerebellum is concerned with movements of the right (left) side of the body ;

  • the brain stem : the stalk from which the cerebral hemispheres and the cerebellum sprout relays data from the cerebrum to the spinal cord and cerebellum and from the spinal cord and cerebellum to the cerebrum - it contains an important set of ascending modulatory neurons controlling the wakefulness & arousal of the whole cerebrum ;

  • the spinal cord : encased in the bony vertebral column and attached to the brain stem, it is the major conduit of all afferent and efferent signals and communicates with the body via spinal nerves part of the PNS.

The outstanding difference between the mammalian and the human brain being the cerebrum and its cerebral neocortex. The total number of neurons in the average human brain is ca.100 billion. Cerebellar granular cells contribute disproportionately to this sum, for there are ca. 20 billion neurons in the typical human neocortex and no less than ca. 109 billion granule cell neurons in the typical cerebellum. Several studies have used neurostereological techniques to estimate the total length of myelin fibers in human hemispheric white matter. Among estimates ranging from 118.000 to 180.000 km, the figure of 135.000 km (84.500 miles) is a reasonable figure to use as the total length of myelinated fibers in the average human forebrain. Stereological measurement of brains from across the human lifespan has demonstrated the neocortex loses 31 million neurons per year in normal aging.

The mammalian brain (or "old" brain) has a two-layered limbic cortical tissue. The ascension from primitive mammals to primates and then humans implied the continuous accumulation of additional cortex (sets of neurons performing sensoric, motoric and associated tasks), curling up as it expanded, forming gyri. In the course of this transition from primitive to more advanced mammals, this "new" cortex expands and increasingly enshrouds the forebrain and limbic system. Most animals lack the most recently acquired six- to seven-layered cortex (or "new" brain"). But all primates with a considerable new brain lack an angular gyrus, essential in the production of complex spoken language (Joseph, 1988, 1990). This angular gyrus, as well as the complexity of the human cortex, are the outstanding neurological structures enabling us to differentiate Homo sapiens sapiens from earlier hominids. In what follows, only the human cerebral cortex is always called "neocortex", whereas mammals acquire "new" cortex.

Parameter Value
number of neurons ca.1009
cortical neurons ca.209 (*)
surface of neocortex ca.11 m²
connections per neuron ca.1000
cortical synapses ca.240 trillion (*)
storage capacity/synaps  1 bit (1/8 byte)

(*) Koch, C : Biophysics of Computation, Oxford University Press - New York, 1999, p.87.

As we shall see, the frontal lobe of the cerebrum is the "senior executive" in the computation of individuality (ego) & volition, as well as (together with the temporal lobe) abstract & creative thought. The cerebrum, especially the frontal-temporal lobes, made possible the explosion of meaning invoked by the Homo sapiens sapiens (Cro-Magnon) and his highly developed neocortex. 

the democratic neuron

Let us step back, and introduce the smallest operational unit of the nervous system : the neuron. Only members of the animal kingdom possess neurons. The neuronal kingdom appeared around 700 million years ago, likely without axons and dendrites, secreting electrical and chemical substances acting on other cells in a general, non-specific way. Then a single, long transmission fiber emerged, the axon, enabling the selective transmission of these messages to a second neuron. Lastly, insulation was invented (myelin or fatty cells wrapping around the axon, preventing leakage).

There are two broad types of cells in the nervous system : neurons and glia ("glue"). There are about 130 billion neurons in the human brain (of which ca. 20 billion constitute the cerebral neocortex) and ca. 1.000 billion glia. The latter are thought to contribute to brain function mainly by insulating, supporting and nourishing neighboring neurons.

Most neurons are in the range of 0.01 - 0.05 mm in diameter. The size of a neuron is at or beyond the limit of what can be seen with the naked eye. The central region containing the cell nucleus is the cell body (or soma), whereas the tubes radiating away from the soma are called neurites, which are either axons or dendrites. The soma usually gives rise to a single axon. Axons act as "wires" carrying the output of the neurons (they travel over great distances of a meter or more). Dendrites (extending rarely more than 2 mm in length) extend from the soma and taper to a fine point. They come in contact with many axons and somata.

It was Cajal (1852 - 1934) who correctly argued the neurites are not continuous from one cell to the next, communicating by contact. Earlier, Golgi (1843 - 1926), the histologist who soaked brain tissue in a silver chromate solution, called the Golgi stain, had maintained the opposite (both shared the Nobel Prize in 1906 but remained rivals). According to the latter, the neurites communicate by way of fusion (a continuous network or reticulum similar to the arteries and veins of the circulatory system). Cajal's neuron doctrine was finally proven with the development of the electron microscope, with a resolution of about 0.1 nm, i.e. a million time better than the unaided eye, distinguishing two points separated by more than one-tenth of a millimeter (0.1 mm).

"A handful of artificial neurons with a dozen-plus connections can learn to tell the difference between apples and bananas. A dozen with a few score connections can be taught to play Hexapawn or tic-tac-toe, perfectly, in a few seconds. Fifty or so, with about 1200 connections, have in reality done a better job of diagnosing heart attacks in an emergency room than a team of expert cardiologists. A hundred neurons, with a few thousand connections, can make money -a lot of money- in notoriously volatile markets. A few hundred can mimic the development of human speech. Of what, then, is the 20 billion neuron, multiquadrillion connection human brain capable ?"
Satinover, J. : The Quantum Brain, Wiley - New York, 2001, p.45.

The structure of the neuron is divided in soma & neurites (axons and dendrites). The internal neuronal process gives rise to two fundamental states of each living neuron : the neural membrane at rest or the action potential. The external neuronal process is summarized by synaptic transmission.

A) THE SOMA

The spherical cell body or soma of the typical neuron is 0.02 mm in diameter. A neuronal membrane separates the inside of the neuron, composed of a salty, potassium-rich fluid or cytosol and a number of enclosed structures or organelles, from the outside. The cell body of the neuron contains the same organelles as those found in all animal cells, they are : the nucleus and the cytoplasm (everything contained within the membrane excluding the nucleus). The details of what happens in the cell falls outside our scope (cf. gene expression, protein synthesis, Krebs-cycle in mitochondria, etc.).

The neuronal membrane (ca. 5 nm thick and studded with proteins), enclosing cytoplasm & nucleus, excludes certain substances floating in the fluid surrounding the neuron. It has been compared to a circus tent draped on an internal scaffolding or cytoskeleton. Its "bones" contain elements dynamically regulated and in continuous motion.

B) THE AXON

This is a structure unique to neurons. It is a highly specialized component for the transfer of electrical current or nerve impulse over distances in the nervous system. There is no protein synthesis in the axon, fed by the soma. It is the different proteins in the axonal membrane enabling it to serve as "wire". If an axon branches, it is generally at right angles (the so-called axon collaterals, which may be recurrent, i.e. return back to the original neuron). The diameter of an axon ranges from less than 0.001 mm to about 0.0025 mm. The speed of the nerve impulse is proportionate to the axonal diameter.

The beginning of an axon (the axon hillock) is differentiated from the axon proper or middle part and from its axon terminal, terminal bouton at the end. The terminal is the place where the axon comes in contact with other neurons or cells, passing the nervous impulse on to them. This point of contact is called the synapse ("to fasten together"). Axons may have many branches at their ends (the terminal arbor) and each branch may form a synapse on dendrites or cell bodies in the same region. Axons may form synapses at swollen regions or "boutons en passant" along their middle part and terminate elsewhere. When an axon makes synaptic contact with another cell it provides innervation to it.

C) THE DENDRITES

A dendrite ("tree") is a branch extending from the soma. The dendrites of a single neuron or dendritic tree has a wide variety of shapes and sizes used to classify neurons (in the cerebral neocortex there are two broad classes : pyramidal neurons -with long axons- and stellate neurons -with short axons-). The dendrites function as the antennae of the neuron and are covered with thousands of synapses. The cytoplasm of dendrites resembles that of axons. Some neurons have dendrites covered with dendritic spines regulating synaptic input.

D) THE SYNAPSE

At the synapse, the nerve impulse is transferred from one neuron to another. The usual direction of this synaptic transmission, gives rise to presynaptic and postsynaptic sides of the synaptic cleft. The presynapse is usually an axon terminal and the postsynapse may be the dendrite or the soma of another neuron.

At most synapses, an electrical impulse traveling down the axon is converted in its terminal into a chemical signal crossing the synaptic cleft. This signal is converted on the postsynaptic membrane into an electrical impulse. This chemical signal is a neurotransmitter stored and released from the synaptic vesicles within the axon terminal. This typical electrical-to-chemical-to-electrical transformation of information is one of the great advantages of synaptic activity and makes possible many of the brain's computations. Modifications of this process is involved in memory and learning. Mental dysfunctions, nerve gas and psychoactive drugs are also related to synaptic transmission, influencing the chemical balance.

In addition to anterograde transport (from soma to terminal), there is a mechanism signalling the soma about changes in the metabolic needs of the axon terminal. This is retrograde transport (from terminal to soma). The action potential of a stimulated neurite does not jump on the membrane of the next neuron, but only runs to the presynaptic side of the synaptic cleft. After a short delay (cf. the transformation of the electrical impulse in a chemical signal and back), this neuron reacts by lowering the potential of the neuronal membrane (or axonal membrane). The level of depolarization increases with the number of stimulating synapses (sum = a + b). Only if at the postsynaptic membrane the depolarization-treshold is crossed will the next neuron transmit the nerve impulse via its axon, etc.

E) REST POTENTIAL

When a voltmeter measures the difference in electrical potential between the tip of a microelectrode inside the neuron and a wire in the extracellular fluid, the inside is ca. -65 Mv with respect to the outside. This is the restpotential or equilibrium potential of the neuron (electrical potential, or voltage, is the force exerted on a charged particle, reflecting the difference in charge between anode and cathode). This electrical voltage is maintained by the neuron. A sodium-potassium pump produces and maintains a large number of K+ ions across the neuronal membrane, leaving the inside of the neuron negatively charged.

F) ACTION POTENTIAL

When an electrical impulse hits a neuron by means of synapses (touching the soma or the dendrites), the rest potential lowers a little (about +10 Mv) and when the threshold of depolarization is reached, electrical couter-forces are released. The neuron "fires" one action potential and this all-or-none phenomenon moves with great speed from soma to axonal terminal (between 0.5 and 120 m/s, depending on the axonal diameter). When the potential enters the axon, the permeability of the axonal membrane changes for a short period, while Na+ ions move to the inside of the axon. For a millisecond, the inside is positively and the outside negatively charged. After this action potential or spike (+40 Mv), the rest potential becomes higher than before (ca. -80 Mv or hyperpolarization), making the membrane refractive, i.e. uninfluenced by nerve impulses. This allows the spike to move further forwards (direction axonal terminal).

G) NEURONAL LOGIC 

The neuron computes the logical operators "and", "or" and "not" as follows :

Suppose neuron A, touched by two synapses B and C. 

  • if B and C are both stimulating A, A fires ;

  • if B or C (or both) are stimulating A, A fires ;

  • C can only stimulate A if B (inhibiting) is not stimulating A.

In reality, a neuron is fed by hundreds of stimulating (yes) and inhibiting (no) nerve impulses. If the stimulating impulses outweigh the inhibiting ones, the neuron "fires". If otherwise, nothing happens and the neuron is "mute". This impulse-frequency can modulate between 0 and about 250 action potentials per second. The "democratic" principle is clear : majority rules. Moreover, although individual neuronal operations have a relatively high margin of error (compared to a computer), they are performed hundreds of times simultaneously. This statistical method guarantees individual errors weigh less on the final result. Another advantage is cortical plasticity : groups of neurons adapting their activity after the destruction of another group (cf. neuroplasticity).

the philogenesis of the human brain

The embryo starts as a flat disks with three layers of cells : endoderm (the internal organs), mesoderm (the skeleton and the muscles) and ectoderm (the nervous system and the skin). Changes in the ectoderm give rise to the neural plate, a flat sheet of cells.

In the neural plate a groove is formed, running from anterior (rostral) to posterior (caudal). The walls of the groove or neural folds, move together and fuse dorsally forming the neural tube. Out of the walls of this neural tube the whole nervous system develops. When folding, some neural ectoderm is pinched off lateral to the neural tube. All neurons with cell bodies in the PNS derive from this so-called neural crest. The process from neural plate to neural tube or neurulation occurs about 22 days after conception. 

The first step in the differentiation of the neural tube is the development at its rostral end of three swellings called the primary vesicles, out of which the whole brain emerges.

primary & secondary vesicles of the neural tube
from Bear, Connors & Paradiso, 2001, figure 7.10 p.182.

These swellings of the neural tube define the fundamental structure of the human brain : forebrain, midbrain and hindbrain. The two cerebral hemispheres grow and lie above and on either side of the diencephalon. The ventral-medial surfaces of these hemispheres have fused with the lateral surfaces of the diencephalon. Unlike the forebrain, the midbrain differentiates relatively little. From the hindbrain, important structures emerged. 

Out of the primary vesicles, the following brainstructure emerges :

  • first primary vesicle : forebrain
    * secondary olfactory vesicles : olfactory bulbs (ventral surface of the hemispheres) - over the course of evolution, a group of primal sensory neurons formed an internally located ganglion of like-minded cells forming the olfactory bulbs, round projections part of the forebrain - from the olfactory system, the limbic system of the "old" mammalian brain evolved (ruled by the amygdala) ;
    * secondary optic vesicles : the two retina's & optic nerve are differentiated - the major target of retinofugal projection is the superior colliculus ("little hill") of the tectum ("roof") of the midbrain ;
    * secondary "telencephalic" vesicle : telencephalon ("endbrain") or cerebrum with its two cerebral hemispheres, basal telencephalon (a pair of amygdala and the hippocampus), the corpus callosum, cortical white matter and the internal capsule ;
    * secondary "diencephalic" vesicle : diencephalon ("between brain") : the thalamus and hypothalamus ;

  • second primary vesicle : midbrain : tectum and tegmentum ("floor"), with the cerebral aqueduct in between ;

  • third primary vesicle : hindbrain : cerebellum, pons ("bridge") and medulla (oblongata).


4 Forebrain, midbrain & hindbrain : structures & functions.


The brain dissected from the skull weighs about 1.4 kg and resembles, in color and texture, a large piece of hard tofu. Its common lateral view shows the "ram's horn" shape of the cerebrum coming off the stalk of the brain stem. The different structures of the brain emerge out of the fore-, mid- and hindbrain (the primary vesicles).

The forebrain develops into the telencephalon (cerebrum, and hidden within it the amygdala-hippocampal complex) and the diencephalon (thalamus & hypothalamus). The midbrain into
tectum, cerebral aqueduct & tegmentum, and the hindbrain into cerebellum, pons & medulla.

In doing so, this development calls into existence fluid-filled caverns and canals inside the brain : the ventricular system. The organization of this system is also used to understand how the mammalian brain is structured. Although deviating from the general mammalian plan of the brain, in particular due to the growth of the temporal lobes of the cerebrum, the embryonic relationships between the ventricles and the surrounding brain still hold. One type of fluid runs in the ventricular system (cerebrospinal fluid).

midsagittal view of the brain
from Bear, Connors & Paradiso, 2001, figure 7.23 p.192.

According to the ventricular system, the following brainstructure emerges :

  • lateral ventricles (first & second) : cerebrum, 2 cerebral hemispheres ;

  • third ventricle : in center of diencephalon ;

  • cerebral aqueduct : in center of midbrain ;

  • fourth ventricle : tube in hindbrain ;

  • spinal canal : in spine.

the ventricular system
from Bear, Connors & Paradiso, 2001, figure 7.23 p.193.


FOREBRAIN

forebrain = telencephalon + diencephalon
telencephalon = cerebrum


TELENCEPHALON

CEREBRUM

the lobes

The many convolutions on the surface of the human cerebrum (the sulci or grooves, and the gyri or bumps) are its outstanding characteristic. They define the major difference between the mammalian and the human brain. This increase in cortical surface is the "distortion" of the human brain, and seat of the processing of reasoning and cognition.

the cerebral lobes
from Bear, Connors & Paradiso, 2001, p.207.

The cerebrum (measuring about 11 m²) is divided into four lobes, situated underneath the corresponding bone of the skull :

  • the frontal bone of the forehead covers the frontal lobe ;

  • the temporal bone (temple) defines the temporal lobe ;

  • the parietal bone (caudal of the central sulcus making the posterior border of the frontal lobe) covers the parietal lobe ;

  • caudal to the parietal lobe, under the occipital bone lies the occipital lobe.

basic structure of the cerebrum

The cerebrum consists of gray and white cortical matter. Gray cortical matter is found in the cerebral neocortex (a thin sheet of ca. 209 neurons lying just underneath the surface of the cerebrum) as well as in the basal telencephalon ("basal" means buried deep within). 

The neocortex is that part of the cerebrum where sensations, voluntary movement, learning, speach and cognition converge. This neocortex (or set of neurons) shares several common features with all vertebrate animals :

  • neurons are arranged in layers or sheet, mostly parallel to the surface ;

  • the layer closest to the surface is separated from the rest by a zone lacking neurons ;

  • at least one cell layer contains pyramidal cells with large, apical dendrites extending upwards & forming multiple branches ;

  • the cerebral neocortex has a cytoarchitecture distinguishing it from the basal telencephalon.

At the beginning of the twentieth century, the neuroanatomist Korbinian Brodmann (1868 - 1918) constructed a cytoarchitectural map of the human cerebral neocortex. Each area having a common cytoarchitecture is given a number. Later, it was put into evidence cortical areas which look different perform different functions. Over the course of evolution, the amount of cortex has changed, but not its basic structure. 

Studying the differences between the neocortex and the primordial cortex of other species (monkeys, cats, rabbits - cf. Kaas, 2001), reveals the human cortex consists of four types of "bark" :

  • primary sensory areas : concerned with the reception of signals from the ascending sensory pathways (all transiting via the thalamus) ;

  • secondary sensory areas : assisting the primary sensory areas ;

  • motor areas : concerned with the control of voluntary movement : these receive inputs from thalamic nuclei relaying information from the basal telencephalon and the cerebellum, and they send outputs to motor control areas in the brain stem and spinal cord. This area is divided into primary and secondary motor areas ;

  • association areas : the remaining areas (particularly in the frontal and temporal lobes) process the recent development of the primate cortex, namely the ability to interprete behavior in terms of mental states.

In the association areas of the cortex of Homo Sapiens sapiens, sophisticated "human" processing occurs. These areas contain neurons able to "associate" or "gather together" neural states from various parts of the brain. Information from the sensory areas, memory systems and the diencephalon (emotional states) is put together and integrated in order to optimalize the possibilities of the nervous system and execute, process, compute & enhance a conscious, aware observation of the world, as well as each individual's efficient and good behavioral, emotional and cognitive responses to it. 

important areas of the cerebrum
adapted from Bear, Connors & Paradiso, 2001, p.208.

Four of these association areas have been discovered :

  • visual association area : inferior temporal cortex : highest integration of visual function & analysis - end station of a system of recognition of specific and particular shapes and objects of interest, both cognitively as well as emotionally - interconnected with the amygdala, hippocampus, limbic system and the autonomous nervous system ;

  • spatial association area : posterior parietal cortex : highest integration of analysis and integration of higher-order visual, auditory and somaesthetic (touch & body position) information - three dimensional image of the body in space - distinction between what is at arm's length (bodily sense) and what is further away (the world) - some neurons motivate and guide hand movements, including the grasping of objects within grasping distance ;

  • verbal association area : angular gyrus, inferior parietal lobe : area of the highest integration of sensory input, with rich interconnections with all other association areas - processes abstract thought and their relation to words (Wernicke & Broca in the left hemisphere) - conceptual comparisons, ordering of opposites, naming of objects, higher logical operations ;

  • volitional association area (also : attention association area) : prefrontal cortex, frontal lobes : receives fibers from all sensory systems (vision, hearing, touch, taste, smell), but has few connections with the primary sensory areas - very interconnected with the limbic system (emotional responses), verbal and spatial association area (conceptual thought and egocentic spatiality) - coordinates highly complex movements and is the "seat of the will", for all goal-oriented behaviors, actions and intentions - able to focus on important tasks through redundancy (screening out superfluous input) - planning, imagining, deciding and attention regulation throughout the cerebrum are computed here, but a complete functional picture is far from clear.

the "human" lobes

The frontal, temporal and parietal lobes are essential in understanding how human consciousness is processed (executed, computed) by the cerebrum of the Homo Sapiens sapiens.

A) FRONTAL LOBE

The evolution of the frontal lobes made possible language (symbolization), tool technology and artistic symbolism. They are the "senior executive" of the brain (Passingham, 1993, Fuster, 1989) and are primary in regard to all aspects of imagination, creativity, speach, language (via Broca's area) and symbolic thinking. In the frontal lobes, the coordination and regulation of attention, individuality, memory and cortical activity is at hand. Intellectual, creative, artistic, symbolic and cognitive processes get executed. They also subserve the expression of melodic-emotional and vocabulary-rich grammatical speech.

B) TEMPORAL LOBE 

Temporal lobectomy on monkeys showed they suffered from "psychic blindness", although able to see things, they did not understand with their eyes what the objects were (cf. the visual attention area). The temporal lobes contain the basal ganglia, discussed in the next paragraph.


C) PARIETAL LOBE

Especially the inferior parietal lobe computes the most human of activities : speech (cf. the verbal association area). Non-human mammals and hominoids lack angular gyri. These apes were limited to "hammering with rocks, and throwing or manipulating leaves, sticks and twigs" (Joseph, 2002, p.347). The control of temporal sequential hand movement, manipulation of external objects & internal impressions are particularly computed by the left angular gyrus of the inferior parietal lobe, unique to humans. 

This gyrus is critically involved in "naming, word finding, grammatical speech organization, and is in part an extention of and links Wernicke's with Broca's area" (Joseph, 2002, p.357).

The vocalization of meaningful sound (manipulating tools in a temporal, sequential manner), multi-classification and multi-modality emerged with the Cro-Magnon. Homo habilis, Homo erectus and Neanderthals "did not posses the neurological sophistication for vocalizing complex human language" (Joseph, 2002, p.358), i.e. angular gyri. The right angular gyrus is crucial in performing artistic tasks. The Neanderthals had more developed occipital and superior parietal lobes (larger in length and breadth), concerned with visual analysis and positioning the body in space (cf. the importance of hunting for the archaic Homo sapiens).


special features of the human cortical cerebrum


A) CEREBRAL HEMISPHERES

The human cerebrum, unlike that of animals, is not symmetrical and each half does not function in the same way. Duplication of effort is replaced by functional specialization in need for cross-talk and collaboration, ensuring each half can do "its thing" without interfering with what the other is doing, while mutual assistance continues to move across the corpus callosum, allowing for the computation of a unified consciousness and sense of "I" unique to Homo Sapiens sapiens.

The "human" reality expressed by the cerebrum is a dual-union, for between both hemispheres information passes back and forth via the corpus callosum, an axonal bridge between the two hemisphere, continuous with cortical white matter (in humans, it is completed between 10 and 12 and consists of a thick "cable" of 200 million nerve fibers). Cortical asymmetry is also suggested by the fact that 90% of all Homo Sapiens sapiens have a preference for the right side, indicative of a dominant left hemisphere.

Following functional differences prevail :

after Joseph, 1993, p.44

Left 
Hemisphere

Right
Hemisphere

linguistic kinesthetic
propositional visual
discrete diffuse
analytical synthetical
verbal visuospatial
discursive
(logical)
presentational (melodic)
digital analogical
specific features broad features
deliberate analogical

This functional asymmetry does not impair the cerebrum to function as a whole. Thanks to the corpus callosum, left and right cerebral approaches may be balanced. Thus, cerebral activity can be summarized under the heading of "the union of opposites", just as in the image of the two scales of the balance. Synchronization of both hemispheres, which are in a constant state of flux, is one of the keys to a balanced approach of life and an healthy response to it.

B) LATERALIZATION

Is the "dominance" of the left hemisphere over the right, i.e. left lateralization, a normal phenomenon associated with the processing of human consciousness by the cerebrum, or rather a sign of a disrupted capacity to process a unified consciousness ? Biofeedback confirms the importance of a balanced (symmetrical, synchronized) cerebral activity. The notion the right hemisphere is somehow inferior, minor or animalistic has been relinquished. Split-brain patients demonstrate how the "silent" hemisphere has a mind of its own ! So, if one hemisphere dominates the other, cerebral activity will be less interesting than in a balanced, two-way cerebral momentum. Each hemisphere performs different parts of an integrated computation. The plasticity of this performance is as extraordinary, as the role of the corpus callosum is essential. The category major/minor is thus interchangable.

"It has now been clearly demonstrated that the right hemisphere is dominant over the left in the analysis of geometric and visual-space, the perception of depth, distance, direction, shape, orientation, position, perspective and figure-ground, the detection of complex and hidden figures, the performance of visual closure, gestalt formation, and the ability to infer the total stimulus configuration from incomplete information, route finding and maze learning, localizing targets in space, drawing and copying complex geometric-like figures and performing constructional tasks, block designs and puzzles."
Joseph, 2002, p.354.

C) INSULA

The insula ("island of Reil
") is a piece of cerebral cortex (the gustatory) bordering and separating the temporal and frontal lobes.

D) COGNITIVE OPERATORS

Cognitive operators are the mind's most general analytical functions or primary functional components (d'Aquili & Newberg, 1999, p.50). They differ from cognitive modules (Pinker, 1999), which represent more specific localized functions. Operators are analogous to those used in mathematics, relating two mathematical elements (addition, substraction, multiplication and division). The seven cognitive operators proposed by d'Aquili & Newberg (holistic, reductionist, causal, abstractive, binary, quantitative, emotional value) have been criticized by Atran (2002, pp.183-184). The reader is referred to the epilogue.


FOREBRAIN DEEP

forebrain = telencephalon + diencephalon
cerebrum = gray matter + white matter
gray matter = neocortex + basal telencephalon


BASAL TELENCEPHALON

The neuronal structures underneath the cerebral neocortex, or subcortical structures of the "deep" or "basal" telencephalon, interconnect the neocortex with the diencephalon.

fore- & midbrain : brain stem and cerebellum removed
adapted from Bear, Connors & Paradiso, 2001, p.211.

Deep within the telencephalon, two important structures emerged : the hippocampus ("seahorse") and the amygdala ("almond"). Together, they constitute the amygdala-hippocampal complex.

HIPPOCAMPUS, the archive-keeper and emotional equilibrator

The hippocampus is a piece of cortex situated in the temporal lobe with only a single cell layer connected with the olfactory cortex (for continuous with the olfactory bulb). It is influenced by the activity of the amygdala and both often act together in a complementary way (emotional interesting sensoric input linked with images, memory & learning). The hippocampus has regulatory effect on the thalamus. It may block (with or without the thalamus) sensory input to the neocortex and regulate the autonomous nervous system by maintaining emotional equilibrium. As such, the hippocampus does not process the generation of emotional states, but memorizes them. Although the amygdala plays as large a part in memory as the hippocampus, the latter serves to both consolidate and construct memory.

AMYGDALA, security agent and emotional regulator

The amygdala are a complex of nuclei situated in the pole of the temporal lobe, just below the neocortex on the medial side, on both sides of the cerebrum. Afferents to the amygdala come from all lobes of the brain. Information from all sensory systems feeds into them, each having a different projection pattern to these nuclei. The amygdala are also connected with the hypothalamus and may activate it, although they modulate & control its drives. They may act at the behest of the hypothalamus and mediate all higher-order emotional functions (spiritual included), have a surveillance function and assign emotional value to stimuli. 

The amygdala may overwhelm the cortex and, in the mammalian brain, they wrested the master control of emotion from the hypothalamus (the "master controller" of the reptilian brain - cf. infra). The amygdala are the master controller of the emotional brain.

Both the hippocampus and the amygdala are part of the temporal lobe, and play an important role in connecting the two parts of the forebrain : the telencephalon (the cerebrum, especially the neocortex) and the diencephalon (thalamus and hypothalamus).

DIENCEPHALON

The diencephalon differentiates into thalamus and hypothalamus. These structures are part of a larger whole, called "the limbic system".

LIMBIC SYSTEM

In 1878, the French neurologist Broca (1824 - 1880) discovered mammals possess a group of distinctly different cortical areas. This collection of neurons formed a ring or border ("limbus") around the brain stem. In his definition, the "limbic cortex" consists of the cortical cortex around the corpus callosum (especially the cingulate gyrus) and on the medial surface of the temporal lobe (including the hippocampus). By the 1930s, it became clear a number of these "limbic" structures were involved in emotion. James Papez proposed an "emotion system" linking the neocortex with the hypothalamus (forming the Papez circuit), each element being connected to another by a major fiber tract (like the fornix, "arch", a major bundle of axons leaving the hippocampus).

To physically experience emotion, the neocortex is critical, but to express it, the hypothalamus is imperative. The cingulate cortex projects down to the hippocampus and the latter down to the hypothalamus by way of the fornix. Upward hypothalamic effects reach the neocortex via a relay in the nuclei of the anterior thalamus.

The Papez circuit is bi-directional :

  • from neocortex to cingulate cortex to hippocampus to hypothalamus
    = expressive (outer)

  • from hypothalamus to thalamus to cingulate gyrus to neocortex
    = experiential (inner)

Because of the similarity between the elements composing both the Papez circuit and Broca's limbic lobe, this group of structures is referred to as the lymbic system (although Broca's notion did not focus on emotion). The limbic system is part of the triune brain (cf. infra).

THALAMUS, the gateway

The thalamus ("inner chamber") is nestled deep inside the forebrain (dorsal part of the diencephalon) and highly interconnected with the neocortex, i.e. the upper walls of the third ventricle. The spinothalamic pathway is the major route by which afferents (registering for example pain or temperature) ascent to the cerebral cortex.

The thalamus is the gate through which information carried by sensoric axons enters the CNS. Here, these afferents are pre-processed to branch out to the relevant cortical areas and the limbic system. It can inhibit the flow to and fro the neocortex, integrates a variety of inputs and translates them into a format the neocortex can read. So the thalamus projects into various cortical areas.

HYPOTHALAMUS, the master controller of the ANS

Philogenetically, the hypothalamus is the most ancient of diencephalic structures. It is situated near the upper end of the brain stem. The inner part of this structure (not larger than a pea) is an extension of the quiescent system, involved with the baseline function of the organism (the parasympathical branch of the ANS) and a subjective sense of peace and calmness ("rest & digest" response). In contrast, the outer edge is the extension of the arousal system, the fight-or-flight response (terror, rage) as well as the experience of extreme positive emotions (from pleasure to bliss). These responses are stimulus bound and die off when the stimulus is removed. Hence, this nucleus is the master control for the ANS (integrates its actions), able to affect every organ or part of the body. It links its operations (arousal or relaxation) to the higher cortical functions. Through it, the latter are able to co-regulate body functions. The hypothalamus also controls aggression, sex and survival-behaviors. It regulates many hormonal systems, including reproductive hormones, the thyroid, growth hormone and moderates hunger, thirst and body temperature.


MIDBRAIN

 forebrain = telencephalon + diencephalon
midbrain = tectum + cerebral aqueduct + tegmentum


The midbrain is only a narrow CSF-filled space, the cerebral aqueduct, with a tectum ("roof") and a tegmentum ("floor"). Although simple, the functions of the midbrain are diverse : a conduit for information passing from the spinal cord to the forebrain and back, neurons contributing to sensory systems & the control of moment, axons descending from the cortex to the brain stem and spinal cord (corticospinal tract), related to the voluntary control of movement.

The superior tectum receives direct input from the eyes. Axons supplying the eye muscles start there (cf. eye-movements). The inferior tectum receives sensory information from the ears and relays auditory data to the thalamus. Of the motoric afferents passing through the midbrain, 90% (or 20 million axons in the human brain) synapse on neurons in the pons. These pontine cells relay this to the cerebellum on the opposite side. The pons is a massive switchboard connecting the cerebral cortex to the cerebellum.


HINDBRAIN

  forebrain = telencephalon + diencephalon
midbrain = tectum + cerebral aqueduct + tegmentum
brainstem = midbrain + pons + medulla
hindbrain = cerebellum + pons  + medulla


Like the midbrain, the hindbrain is also a conduit of information passing from the forebrain to the spinal cord and back. Its neurons contribute to the processing of sensory information, the control of voluntary movement and the regulation of the ANS.

To regulate the overall activity-control of the brain, neurons with a particularly widespread pattern of axons are called in. They use particular neurotransmitters and have widely dispersed, diffuse connections, modulating vast assemblies of postsynaptic neurons, such as the cortex, the thalamus etc., causing them to be more or less synchronously active (more or less excitable). These very diffuse modulatory systems share common features :

  • they consist of a small set of neurons (several thousand) ;

  • they arise from the core of the brain, most of them from the brainstem ;

  • each neuron has an axon contacting more than 100.000 postsynaptic neurons across the brain ;

  • their axons have a transmitter which is not confined to the vincinity of the cleft, but diffuse to many neurons.

THE RETICULAR FORMATION, the gate keeper, the filter, the master modulator

The ca.12.000 neurons of the tiny locus coeruleus ("blue spot" because of the pigment of its cells), of which we have two, one on each side, have axons fanning out to innervate about every part of the brain. One neuron can make more than 250.000 synapses and can have one axon branch in the cerebral cortex and another in the cerebellar cortex. On either midline of the brain stem lie the nine raphne ("seam", "ridge") nuclei. Each nucleus projects to different regions in the brain. Together with the locus coeruleus, the ascending reticular activating system (ARAS) is constituted. This is the "core" of the brain stem, involved in the regulation of attention, arousal, sleep-wake cycles and general metabolism of the brain. The ARAS system arouses and awakes the prefrontal cortex. Raphne neurons control the sleep-wake cycles and well as the different stages of sleep.

a diffuse modulatory system : the locus coeruleus
adapted from Bear, Connors & Paradiso, 2001, p.515-518.

In this region of their brain, humans assemble a "set of instructions" for purposes of long-term storage (MacLean, 1976), with dreams playing an important part in this process & integration in general. The general immediate assessment of place, time & person followed by ongoing evaluation is the automatic, "instinctual" orienting response (also acting as a filter to block certain inputs) processed here.

REGION OF CNS EXECUTIVE FUNCTION
neocortex higher order cognitive, affective and motoric processes
cerebral hemispheres concert of analytical and synthetical higher-order approaches
prefrontal cortex senior executive of all
higher order functions
cingulate gyrus willful acts, intent
angular gyrus senior language controls
threshold between cortical & subcortical structures
hippocampus memory consolidation
and emotional equilibration
amygdala security and emotional regulation
thalamus universal gateway
integration & projection
hypothalamus master controller
of the ANS
limbic system overall emotional circuit
ARAS filter and master modulator
ANS basal neurophysical activity

cerebellum

The cerebellar cortex is an important movement control center, receiving massive axonal inputs from the spinal cord and the pons (position of body in space). Goals of intented movements originating in the prefrontal cortex are relayed via the pons. The cerebellum compares and calculates the sequences of muscle contractions required.


5 The triune brain : reptilian, mammalian and human.


Neuroscientist MacLean (1970, 1978, 1990) advanced the concept of the triune brain. In the brain as a whole, he identified a three-tiered structure, called "reptilian", "mammalian" and "neocortical". This division has been used by neurophilosophy and contemplative science to explore the meeting between religion and neuroscience (Albright & Ashbrook, 2001). MacLean and other researchers have observed animals whose activities depend on each of these "brains". In this way, various functions have been attributed to each of these three parts of the brain, characterized by a different structure and chemistry, yet extensively interconnected.

  • the reptilian brain : brain stem (midbrain, pons, medulla), midbrain, hypothalamus ;

  • the mammalian brain : thalamus, hippocampus, amygdala ;

  • the human brain : neocortex of cerebral hemispheres of cerebrum, angular gyrus.

Compare this with the anatomical division of the brain in fore-, mid-, and hindbrain :

Reptilian brain = hindbrain + midbrain + hypothalamus (the "oldest" master controller) ;
Mammalian brain
= higher thalamic diencephalon + basal telencephalon (hippocampus and amygdala, the "old" senior executive) + cingulate cortex (relay to cortex) ;
Human brain = forebrain, neocortex (the "new" senior executive, in particular the prefrontal cortex).

In this context, stress the difference between mental states of which the subject of experience is conscious (processed by the neocortex, in particular the prefrontal lobes) and those remaining unconscious (processed by the dominated hemisphere, the limbic system and the brainstem). The former can be studied directly (for direct conscious feedback is possible), whereas the latter is made evident in the emotional coloration of information and the regulation of the overall wakefullness of the brain. The present neurophilosophical investigation aims at a partial, incomplete & provisional understanding of the nervous system as a whole, i.e. peripheral nervous system included. The studies of Maclean accommodate such an approach.

A) THE REPTILIAN BRAIN

The behaviors of reptiles are ritualistic, conservative and "programmed", with no playfulness, joy or sadness. There are 4 main types of reptile display or rudimentary communication :

  • signature display : reptiles share signals to help identifying members of the same species ;

  • courtship : signals to attract the attention of the opposite sex ;

  • territorial challenge : instinctual attempt at deception to fend off invaders or attackers ;

  • submissive/dominance : strict hierarchy and ritual submission allows the group to survive.

In the reptilian brain of non-reptiles, the territorial imperative (cause of war) is still at work, in life support and self-protection. In reptiles, the latter is often realized through deception, imitation & secrecy (cf. the treacherous serpent, the violent crocodile, the cowardly cameleon, the slow tortoise). The responsive (not reactive) nature of this brain, makes it suitable for guarding, patrolling and vigilance, which are bound to routine, precedent and ritual. The conservatism of this brain is stabilizing, and routinizing saves energy. However, a failure to adapt, is characteristic of it. In the brain stem, addiction & deep memory storage through dreams are processed. The reptilian brain houses the more violent, aggressive -even murderous- expressions of impersonal sexuality, expressing a vertical, hierarchical, dominance/submission signal communication. 

the reptilian brain has two major neurological structures : 
the ARAS and the hypothalamus

This earliest brain and its "automatic pilot" are anchored in the embodied, the concrete. It has no emotions and no language, except signals. Traditional religious, philosophical and cultural systems (computed in the prefrontal cortex) devise rituals to exorcize (banish, cast out or at best tame) the troublesome and unwholesome urges & drives of the reptilian brain and keep one "pure". The whole strategy is dualistic. By dividing and ruling, theologies do not assist in the integration of the triune brain, which, on the lowest level, implies a rhythmical ride "on the back of the crocodile", knowing the precise momentum to co-opt "the Monster" and to create a win-win situation instead of making us captive of the division between the "law of God" and "the law of sin that dwells in my members" (cf. Paul, Letter to the Romans, 7:21-24).

B) THE MAMMALIAN BRAIN

Reptiles fight without excitement, show no panic at being prey and display no hot-blooded couplings, just ritualized (at time violent) behavior. Mammals, to a greater or lesser degree, exibit anger in competition, cravings for food and lustful drives to mates.

Emotion is the motivating & mobilizing source of empathy and memory and unites relatedness and nurturance. In reptiles, the limbic structures around the brain stem are present in abbreviated form only. They are found in all mammals and specialize in attaching emotional labels to the incoming and outgoing streams of information. This brain is able to trigger emotions related to eating, mating, fighting (food, mates), the care of the young, play & community. Relating and nurturing are the essential feature of this brain (Albright & Ashbrook, 2001, pp.85-86).

the mammalian brain has three major neurological structures : 
the thalamus, the hippocampus and the amygdala

Emotion labels this-or-that as something which matters to us. Emotion adds colour & affect to mental states. Emotion enables permanent storage (in the brain stem), suggestive of the ongoing activities between the three levels of the living brain, computing mind. While emotional memory is formed and its individual, emotional aspects stored in the amygdala, cognitive, visual and contextual variables are stored (recalled) by the hippocampus (Gloor, 1997).

C) THE HUMAN BRAIN

To be able to compute all higher-order operations is the "nominal" mode of working of the cerebrum and its specific, bi-modal approach : two hemispheres processing one integrated cerebral activity from two different angles. Abstract thoughts can be thoroughly computed after the axonal bridge between both, the corpus callosum is completed (cf. Piaget's "formal-operatoric phase" after the age of 10).

Contrary to the reptilian, mammalian and all other cortical brains on Earth, the neocortex of Homo Sapiens sapiens is exceptional in size, wiring & function. Of all mammals, humans have the most "uncomitted cortex" at birth (Penfield, 1975), i.e. fewer neurons with, in their hardware, instinctual patterns built-in. This implies the human brain is made for organic neuroplasticity (the more difficult a task, the more cells process it) and also has great ability to learn and individualize.

the human brain has one major neurological structure :
the neocortex

The bi-modality of the human brain is horizontal & vertical. On the horizontal horizon, there is the joint project of the two cerebral hemispheres : cerebral activity is called to be an integration of a duality. This is accepting the difference while opening up as many neuronal alleys between the hemispheres (cf. the "concordia discors" of thought in Criticosynthesis, 2008).

Vertically, the neocortex (or upper telencephalon) and the basal telencephalon perform different tasks Although 95% of right-handed people have left-hemisphere dominance for language, only 18.8% of left-handed people have right-hemisphere dominance for language function.

The basal telencephalon is part of the limbic system. It is essential in the relay of information down from and up to the neocortex and adds "emotional color" to what comes in and goes out. Especially the amygdala play a crucial role in this, while the association of memory & emotion is noteworthy.

  • left hemisphere/neocortex : higher order verbal operations ;

  • left hemisphere/basal telencephalon : emotion/word associations, digital memory ;

  • right hemisphere/neocortex : higher order visuospatial operations ;

  • right hemisphere/basal telencephalon : emotion/imaginal sensations, visual memory.


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initiated : 01 V 2003 - last update : 17 XI 2009 - version n°3