III

Everything and more − THE LIMIT

The child proceeds, resolute but careful, he places his foot with studied measure. Two long steps, a short one, two more small steps, a longer one. He made it!, he crossed the whole paved ground without stepping on any junctions between two tiles, without betraying any one of the abstract and inviolable limits that marked his way.

Oh, not easy at all to escape this, even when you grow up. Yes, as it is not so easy to connect with four straight lines, without raising the pen from the paper, these nine dots: (for those who, although so conspicuously helped, have not found the way, the solution is here).

The trouble is that the limit strikes us, attracts us, hypnotizes us. And limits us.

We are too accustomed by the reality if objects to see their profile and border, to recognize where the limit separates the ground from the sky.

Uncertain borders thrill as dangerous transgressions. They fascinate, they certainly do, but they awaken, intense, the desire of terra firma, of solid and reliable ground onto which to place our feet. So, it ends up that we go searching for clear limits and borders, even where there is no reason for them to be there, simply not to get confused, to be able to discern and orientate.

Still, in front of life, that relies on changing to subsist, on remodeling, and overcoming at any moment the border with the world, with external reality; in front of life even our sublime capacity of imposing names, and borders and limits and differences, turns out inadequate. We feel as unavoidable the need to reconcile two approaches, two perspectives, matter with its laws and something different, other, that requires a gaze receptive of vague, and vanishing aspects, aware of multiplicity.

Yes. Life puts us in trouble. At what moment the caterpillar, hidden in its cocoon, is no more a caterpillar and has become a butterfly? And leave alone the question of embryos, and vegetative life, and postponed deaths, and when does the soul arrive and when does it leave... Accustomed to the obvious limit that encloses a body, separates two types of matter, gives reality to objects, we feel as if we had to separate and dissect in the same way events, processes and developments that gradually, more or less rapidly, flow through different phases. It might be indispensable, it might be useless. Certainly, it is difficult: few things are so clearly different from one another as life and death are, but still it is not easy to grasp the precise border.

This happens precisely because what has no life only persists when it is so strong or protected that it cannot be attacked and modified, but life can only sustain itself by continuously changing, by eroding the limit; life confirms itself by negating in any moment what it has been before, by overcoming the border between how it is now − what it is in this moment − and how it will be, what it is going to be.

Life thus persists by eroding its limit. So, it might be appropriate to try and change our perspective on LIMITS in general, and consider them as lines of passage, of interaction. Does this mean that we can extend the approach that works so well in simples domains of our knowledge to any other, more complex domain? Does this mean that physics can explain, in addition to forces and processes in the inanimate world, also our life, maybe even our thought, as if we were simply built using interchangeable circuits, the same for all of us?

Certainly not. Nobody would dare stating our circuits are interchangeable. Actually, not even my own are the same as they used to be yesterday, we must talk about this later. Thus, certainly we are not reducible to circuits, formulas, waves, equations.

We are not reducible!

But if the question were the need of changing our view, not on ourselves, but rather on Physics?

If the fundamental problem of reductionism were that it is wrong not only and not so much to try and reduce the soul to equations, but rather to try and reduce Physics itself to equations, and overlooking indeterminacy, un-knowableness, charm, wonder and poetry in the things, in the world, in Physics?

To this purpose, a new outlook is real necessary.

Physics are clear, reassuring (ok, do not panic, I am not nuts, I shall explain straight away what I mean). Objects, energy and measurable forces. Precise and finite things, limits, causal relations. The relations may be complex, and where relations are complex and ordered it appears there must be a project. But it is not so; as long as it is a matter of physics, phenomena are nothing but the inevitable result of the factors and the forces involved.

But our everyday experience is marked by man. Events guided by motivations and aims, more or less explicit, transparent, valid. More obscure, mediated, inaccessible are the causes. And where causes and mechanisms are masked and difficult to perceive it is easier to imagine motivations, aims, or some form of will whatsoever, arcane and arbitrary as it might be. Arbitrary, precisely, because this is the domain of life in general, and the quintessence of human life: arbitrariness, freedom from material causes, no ineluctable, necessary mechanisms − hidden as you wish but coherent, predictable, at least if you know enough, never arbitrary.

This is a comfortable, malleable, powerful and satisfactory interpretative paradigm. A simple perspective, effective, tranquilizing: what is not inevitably produced by evident physical causes is produced by choice and will, sensible or absurd as they may be, choice and will that are human. Or, where no man appears to be involved, divine.

It is the perspective of the child, who only grasps a few causal relations, and in all the rest he sees the omnipotence of the adult at work.

It is the perspective of myth: when you run out of physical explanations, entrust yourself to the omnipotence of the gods.

It is not stupid credulousness. In some respects, this is also Aristotle’s perspective, cautious and creative, systematic and sharp: to build a house you need bricks (material cause), a mason (efficient cause), the project (formal cause) and the need of a roof to cover you (final cause).

There must be an aim and a design, a project. Wherever Man is involved.

But not in all things is there an aim, a project. One has to be able to stop. One must recognize where formal and final causes are not necessary, and their only scope is to fulfill the ancestral need of attributing to a superior mind the design of an order that appears to be too much accurate to be born from itself, so accurate that, once it is put in motion, it can persist indefinitely, by simply applying causal rules that do not ask for the intervention of any will any more, of any skipper, of any god − except for realizing miracles, i.e. by infringing and humiliating the rules.

All that we know today permits us to read storms and eclipses, planetary orbits and earthquakes, holes in the ozone... and even the extinction of dinosaurs, the architecture of anthills, the language of bees, and Sybille’s epileptic convulsions too, without bothering any higher wills, formal causes, finalisms, demons or providences.

The history of man is a story of ever new readings: each new discovery displaces the border between physics and metaphysics. Between a theory of causes and a theory of aims.

Physics and metaphysics. Maybe there, the border is there, where causes do not suffice any more and choice, motivation, aim and will intervene. Man’s will, or the design of fate, the arbitrariness of a god. And as long as a frog only goes cra-cra, and runs away from noise and jumps to catch flies, with all the complexity and finesse of the mechanisms and processes that have brought it there, since when it was a tadpole, with all the wonder of life that pushes it and guides it and pervades it; well, as long as it always and only does what you expect it to do, it is difficult to concede it a soul.

Maybe there, deep in our heart, in that mayhem where we pick our sensations and judgments, so clear-cut and definitive that they seem to have been profoundly engraved there by somebody else, before, since the beginning... maybe there one can find how to recognize the soul. It is where there is possibility and capability of choice, it is where the reading of the world is not mandatory, where the gesture is not only instinctive, where a behavior is possible that does not necessarily follow one’s own interest − and not because of a protective or species instinct, no, − where it is possible that the behavior be guided by something else, by social, altruistic, ideal values, by forces that are not causes arising from the world of things, but rather motivations, aims, aspirations, dreams, passions, that come from somewhere else, from what we have always liked to call the world of ideas.

But if this is the border, then science must dare go over, invade CHOICE and WILL. Because many aspects of the neuronal mechanisms of choice, of motivation, of behavior finalization have by now been clarified.

Here comes again the problem of limit, separation, diversity, «other».

Is the soul «other», then? Is the world of ideas «other», something else of which material reality is only a deceptive simulacrum... Something else that has nothing to do with, that one can agnostically disregard, captured by the frantic fibrillation of real world...

This is the fracture that today should become a border, to courageously trespass: physics, guided by causes and laws, on one side; and metaphysics, guided by choices and aim, on the other; science on one side, poetry on the other. Perhaps, this is precisely the way: a science that does not surrender poetry. A science that does not fear the limit, that is able to look at life as a process and to venture to study the soul, at least as concerns all that in it can be reasonably explored, investigated, known, understood.

To perceive these new perspectives it is necessary to exercise in looking at each aspect of reality, and knowledge process, from both inside and outside, in appreciating the limits of each single approach and each logic, though not repudiating it when one goes further and looks beyond.

To understand where the roots of all this lie in the brain, however, it is necessary to avoid getting stopped by limit, to really be capable of meta and to manage in perceiving the relationship among worlds that are different, “other”. One has to try and overcome the sensation that “ok, the brain as far as you wish, but the soul begins where the brain ends”.

Perhaps the LIMIT is not the only problem. But it is not by chance that the problems that are most difficult to solve are those that require trespassing a limit, evading a frame, a scheme that nobody has imposed to us, but we ourselves have imagined to be there to stop us, insurmountable.

If one accepts this fracture between the physical perspective, guided by causes and laws, and metaphysics guided by choices and aims, the relation between mechanisms and active deeds becomes blurred, the field of research, exploration and empirical investigation is abruptly and unduly reduced, the gap between scientific approach and humanistic culture gets widened further, and the logic and culture of limit is strengthened. But this should be the time of great unifications! It should be about time to understand that a same place, calm and welcoming, can host meditation and prayer of believers of any religions. Time to understand that different perspectives add light and depth, and do not fragment but rather expand comprehension and knowledge, that different logics do not discourage and divide but rather help understanding reality and life in their splendid complexity.

It should be about time, because the healthy part of culture has overcome the need of contemplating inexistent monotonous universal harmonies and totalizing coherences, more or less revealed. Exact sciences have denuded dogmas by showing unexpected impotencies. Gödel has been able to sublimate mathematics and logics, by showing that no logical system can be coherent unless it admits a limited field of application, and cannot be complete unless it accepts some incoherencies: it is not merely word-games, the phrase «this sentence is false» does not admit any judgment of truth and is an example of a clearly demonstrated property of any formal system: its rules can be clear and coherent only if they apply to a limited domain and do not demand to be apply outside its borders. The logics of true and false do not apply to discussions about the truth. Euclidean geometry does not apply to a universe where nothing is flat. Galilean physics do not apply when speeds approach the velocity of light. And the laws of Physics do not apply to the soul. But one can build logics that deal with criteria of truth without being able to tell the truth of specific statements; one can build geometries in which parallel lines do not make sense, but that can describe curved universes; one can state and demonstrate theories of the Relativity that analyze physics in the neighborhood of light speed and redraw space and time and matter and energy, and the infiniteness itself of the universe. And always with coherence and rigor, putting these systems side by side, although each of them, inside itself, obeys inviolable rules that do not apply in the other systems, and negates applicability to fundamental principles of the other systems.

One can construct perspectives capable of exploring the soul, using instruments that have no use in physics and putting aside physical laws that cannot say anything about the soul. On can do this without imposing physical causality outside its limits, but nonetheless without subtracting from physics all that changes and lives; without searching for mechanistic interpretations of dreams and love, but nonetheless without confining aspirations, passions, forces and flights of the soul in a cave of the ideas, in a limbo of revealed truths, in a mystical ether that reason could never reach.

One may ask why the block imposed by the concepts itself of limit is so difficult to overcome. At least two factors play an important role: first, trying one’s own breeches on the world is convenient, the limit simplifies, overlooks problems, reduces distress; in addition, and this is a more subtle and elusive factor, the limit disputes evolution, crystallizes, underscores the antithesis between preservation − protection, defense − and change, between coherence and development; it generates and sustains the horror for new and «diverse».

When I was young and Marxist (I can’t be proud of being young any more and, alas!, it appears that no one might be proud of being Marxist any more) I wanted to write a book (yes, sooner or later it was bound to happen) about the limit. About giving names to things to trap them, separate them, disarm them.

Like any organism, social organization persists by evolving and changing its relationships and interactions, within itself and with the outside. The health and adequacy of an organism are related to the coherence between the dynamics of the subsystems that constitute it and the overall dynamics of the entire organism, the forces that move it. Life is based on the simultaneous presence of forces and mechanisms that tend to consolidate and reproduce the prevailing organization, and forces and processes that push to interact with the outside, suffer changes, and evolve by guiding such changes. So, the conflict between components of the society that act to maintain unchanged the equilibrium of the momentary social, political and economical conditions − generally because of their conditions of privilege − and components that push to change − generally moved by their disadvantaged conditions, or possibly by ideal forces − presumably is not a sign of social suffering, but rather of vitality. Indeed, this might be the greatest scientific flaw, and ideological limit, of historical materialism, of the analysis of antagonistic modes of production, of the idea itself of a society with no classes, non-antagonistic.

It is true, however, that the dominant classes and lobbies, that are «automatically» inclined to preserve the momentary sociopolitical status, greatly profit (indeed, the status itself greatly profits) of a diffuse fear and aversion versus any change, that is perceived as limit, negation, destruction, and therefore the dominant culture tends to be strongly founded on the concept of limit, separation, diversity, as a bulwark in defense of the existing (entities, rules, relationships, perspectives).

The solidity and stability of a social system (in particular an antagonistic, not equalitarian, system) is based on and measured by the force with which the limit, the fear of diversity and exclusion, the aspiration to homologation, are imposed and profoundly rooted in common thinking.

But the inability to see the limit as a line of encounter-passage-communication, rather than separation, to see change as evolution, rather than diversity and negation, precludes any serious analysis of life as a process. Even more − let’s say it finally − it precludes any serious analysis of soul, at least of that which in it can be somewhat explored, known, analyzed, understood.

Thalamus and hypothalamus

Anterior to the midbrain we find two fundamental structures: the hypothalamus, the highest center of coordination of visceral and vegetative information, and the thalamus, the last stage for all input signals to the cerebral cortex.

The hypothalamus is in charge of maintaining homeostasis, that is constant values for all vital parameters. Blood pressure, body temperature, blood levels of sugar, oxygen and carbon dioxide, water/electrolyte ratio, etc., are maintained and controlled by coordinating all visceral and vegetative responses. The hypothalamus regulates cardiac activity, renal function, vasoconstriction and dilatation in various districts, gastro-enteric activity, sweating, sexual organ functions. Supervision on all these functions is exerted through three systems. The first system of vegetative control is the autonomous nervous system (orthosympathetic and parasympathetic), that innervates the heart, blood vessels, visceral muscles and glands. The second control mechanism for vital and vegetative functions is the production of hormones, some of them by the hypothalamus itself, others by the hypophysis (the small, pituitary gland located above the roof of the pharynx, just below the hypothalamus) under its strict control. The third, fundamental control mechanism is the generation of neuronal signals that are distributed to various nervous structures of the brainstem and higher centers, to ask for the performance of voluntary activities: in higher organisms, in fact, it is not possible to maintain homeostatic equilibrium, and therefore not even a mere vegetative survival, without performing active behaviors, such as searching for food and water, behaviors aimed at protecting from heat al cold, sexual and reproductive behaviors. It might be appropriate to pause for a moment considering these aspects: without voluntary activity man cannot survive, even though he may breath and posses healthy heart, liver and reins, unless one attaches him to machines that nourish and hydrate him, and protect him from extreme temperatures.

Above the hypothalamus, a big structure with the shape of two collated globes, the thalamus (this is the ancient word for nuptial bed, presumably there were no king-size mattresses at that time), constitutes the last stage of organization and control for the information that must reach the cerebral cortex. The thalamus performs an essential function of elaboration and filtering on the passing information. If the thalamus prevents the sensory information from reaching the cortex, the latter works in a completely different way, by elaborating according to its own rhythms in a state of altered conscience, independent of sensory information (sleep).

Cerebral cortex

The cerebral cortex constitutes most of the mass of the encephalon in man. Cortex development is what mostly differentiates human encephalon from that of other animals, even primates. In less brilliant animals, the cortex constitutes a small portion of the encephalon, almost an optional accessory, which suggests that it must not be strictly indispensable to permit the animal to correctly react to stimuli and behave in the most appropriate way. This is why the doubt arises that looking at man’s brain − and possibly woman’s one, in particular − as a mere instrument to optimize behavior, in a stimulus-response logic, might be a little minimizing, and might not let us grasp, perceive and taste its potentialities and its essence itself.

The cortex constitutes two hemispheres, characterized by a rough and complicated surface, similar to the kernel of a nut, rich of ridges (cortical gyri) separated by troughs. In lower animals, actually, it is much less bumpy and jagged. Cortex organization is symmetrical in the two hemispheres, even though several higher functions in man are performed in an asymmetrical fashion by the right or left hemisphere.

Information reaches the cortex mostly through the thalamus; in general information coming from the left part of the body reaches the right thalamus and hemisphere, and vice versa. The various cortical areas are intensely interconnected by massive bundles of axonal fibers (white matter) that run partly on the surface and partly in the depth of the cortex. The two hemispheres are strictly connected by an antero-posterior arch of white matter (callous body) that is constituted by a massive ribbon of transversal axon fibers. The hemispheres enclose a large mass of nervous tissue, located in the lowest central region: a region where white connection areas alternate with gray regions of neuronal bodies with their intricate local connections (basal ganglia or nuclei).

A major fraction of cortical elaboration is relayed to the cerebellum and basal ganglia. Both structures return their own elaboration to the cortex, through the thalamus, although the cerebellum also has direct output connections towards the brainstem. The function of these reciprocal connections of the cortex with the cerebellum and basal ganglia is very important, and will be discussed later.

Learning

Most functions in cells are performed by proteins, large molecules that can change their shape (more properly conformation). When they change their shape some proteins may bind chemical substances and bring them together in such a way to favor a specific chemical reaction (these proteins are called enzymes); other proteins may move molecules or cellular organelles along filaments, or slide different filaments on one another to produce movement (muscle contraction, for example); other proteins may be inserted in the cellular membrane and cross it: by changing their shape they can transport small molecules or electrolytes, or let them through in a regulated way, from one side to the other of the membrane. Briefly, by changing their shape proteins control and regulate all the chemical activity of the cell, produce movement, define the composition of the internal fluid in the cell and its organelles, and produce the electrical activities of the cell, that are generated by the active transport or the passive flux of ions, which are electrically charged, across the membranes. In turn, the proteins are regulated and modulated in various ways by the momentary − rapidly reversible − binding of ions or small molecules, or by the electric field, or following modifications in their chemical structure (by adding /removing pieces of the molecule) that are in turn produced by other enzyme-proteins. Finally, the presence itself of each protein, and thus the function it performs, can be regulated by controlling its synthesis starting from the gene that codes for the protein.

In nervous cells, the response to the neurotransmitter, the elaboration of the electrical signal and the secretion of transmitter molecules can be regulated in thousands of ways by influencing the activity of the proteins involved. The functional organization and the number of the synapses can also be modified by changing the activity of proteins. The crucial point, in nerve cells, is that one of the most efficient and flexible means to modify the activity of their proteins is electrical activity itself. As a consequence, neurons modify in time many of their properties, and may strengthen or weaken synapses, or even destroy them or make new ones, and all this as a function of their own activity, or in other words as a function of the information their are elaborating. Thus the functionality and organization of neural circuits, in their complex, and the way they process information, change as a function of the information itself they are elaborating. This constitutes the cellular basis of the capacity of neural circuits − and of brain in the end − to learn, and the cellular basis of memory.

Typically, a synapse can be strengthened if it is stimulated in an intense and repetitive way. However, the fundamental characteristic of learning processes in the central nervous system is associativity: a synapse strengthens, or in some systems weakens, when it is activated several times in synchrony with a nearby synapse, or just after it, with the result that the neuron learns to respond to one of the two signals with the same intensity with which it used to respond to the simultaneous occurrence of both of them: when two stimuli appear associated, several times, to a neuron, this learns to respond to one of them alone as if the other were also there. And it is sufficient to recognize some elements to have the brain work as if it had recognized the whole, it is enough to recognize a few tracts of a face to feel the pleasure that we have experienced in the past with that person...

The “paleo-cortex” and the limbic system

The most “ancient” portions of the cerebral cortex, that first are found in ascending the evolutionary staircase, are in charge of extracting signals that request a behavioral response, from pain, sensory and visceral information, and of generating the necessary signals to coordinate such response. They are regions in which the most rudimentary aspects of “emotional” life are elaborated (pain, pleasure, well-being, distress), together with the resulting “motivational drives”, capable of producing active behaviors, not simply reflex but autonomous reactions. In lower animals the schemes for the execution of such behaviors − such as fetching food, building a lair, courting and sexual activity − are already pre-cabled to a major extent in the sub-cortical neural network, and constitute instinctive behavior. Therefore, the role of the cortex is almost exclusively that of evaluating the opportunity of instinctive behavior, possibly choosing the appropriate response among several different possibilities, and of triggering such behaviors in the appropriate situation and moment. The structures that constitute this portion of the cortex are in strict connection with the hypothalamus and with two nervous structures that have a rather precise function and a marked learning capability: amygdale and nucleus accumbens.

The amygdale is an almond-shaped nervous nucleus, whose neurons have the job of discharging impulses when signals that indicate danger reach the nervous system. The amygdale not only responds to signals instinctively associated to danger, but learns to recognize other signals associated to danger, based on experience. Activation of the amygdale at increasing levels triggers the visceral, mimic and behavioral reactions typically associated to anxiety, fear and terror.

The nucleus accumbens is a lower lateral portion of the basal ganglia, that receives information from many regions of the central nervous system and is in charge of detecting the possibility of satisfying a physiological need or obtaining a gratification. When this happens, the neurons that have recognized the possibility of well-being start firing, thereby acting as a powerful source of motivational drive (anticipation) to enact behaviors that are adequate to obtain the desired result. A further important pathway that reaches the nucleus accumbens comes from regions of the midbrain (the VTA) that are activated when a positive event occurs, a need is being fulfilled, a distress is overcome, or a situation of well-being has been reached. This neuronal connection is said «reward pathway» and produces an activation of the nucleus accumbens that performs two different and equally important functions: first, this activity of the accumbens underscores the condition of pleasure and gratification; second, this activation contributes to train specific neurons in the accumbens itself to fire in the future, every time a situation occurs that may lead to this same gratification. The capacity of directly or indirectly activating this neuronal pathway is shared by many drugs acting on the nervous system, such as nicotine, amphetamines, cocaine, heroine, and constitutes the fundamental mechanism by which these drugs establish a condition of psychological dependence.

These two structures (amygdale and accumbens), together with some other communication pathways and the most ancient portions of the cerebral cortex (in the innermost portion of the brain, where the two hemispheres face each other) constitute the system that performs the general elaboration of emotions and motivational drives, the so-called limbic system. The name itself is evocative, as if it were to indicate the region where deep urges, physiological needs, pain and pleasure approach, through emotional elaboration, the threshold of conscious perception: a “limbo” in between the storms generated by conflicts among vital urges and the ethereal lands of conscious cognitive elaboration.

Cerebral cortex specializations

Each cerebral hemisphere is crossed by a transverse furrow (central or Sylvius fissure), approximately at the center of the skull, that separates the anterior part (frontal lobe) from the middle-posterior part (parietal, temporal and occipital lobes). In vague analogy with the organization of the medulla, all the posterior part of the cerebral cortex is involved in the elaboration of sensory information (“input” to the brain), whereas the anterior part is involved in the elaboration and programming of behavior (“output”).

In particular, the posterior part of the cortex (occipital lobe) elaborates visual information. Auditory information is elaborated in the temporal lobe. Taste information is elaborated in the internal region of the temporal lobe and olfactory information more anteriorly. Just behind the central fissure, a stripe of cortex of the parietal lobe elaborates somatosensory information − tactile and skin sensory information, and proprioceptive information from joints and muscles that make it possible to know the position of each body segment at any moment. This cortex stripe is topologically organized: information coming from the foot reaches the central region (toward the top and center of the head), while information from higher levels is distributed to more lateral and lower regions, thereby drawing a species of small monstrous man, upside down on the surface of the cortex, a warped troll with short and small legs, tiny chest, huge hands, wide face and an enormous tongue, because the quantity of cortex dedicated to each region of the body depends on the quantity and importance of the information coming from that region itself. The “homuncule” on the right parietal cortex reproduces the left part of the body, and vice versa.

Anterior to the central fissure, facing the sensory homuncule, a motor homuncule can be drawn on the surface of the frontal cortex, deformed in about the same way: this stripe of the frontal cortex constitutes the primary motor area, which is responsible for the voluntary control of muscles in the contra-lateral part of the body. In the motor area many neurons (pyramidal neurons) send their signals directly to the neurons of the anterior gray matter of the medulla − motor neurons − which directly activate skeletal muscles.

In addition to these regions with sensory and motor functions, the cortex comprises the above-mentioned limbic areas, more “ancient”, that elaborates information with emotional relevance.

Associative cortex

The regions of the cortex described up to here − limbic cortex, primary visual area, other primary sensory areas and primary motor area − comprise most of the cortex of a mouse, but they only account for a minor fraction of human cortex. Each primary region is encircled by “associative” cortex, that elaborates in a thousand different ways the information present in the corresponding primary area. In man, other areas are even more developed, broad and important: they are the regions in between these associative areas, that compare and relate information obtained through different sensory modalities (multimodal associative areas).

Thus, in man most of the cortex is taken by associative areas, and in particular multimodal areas. This is particularly true for the frontal lobe, which is tremendously developed in man with respect to any other animal, and is not only capable of programming the most refined movements, but also of elaborating a complex behavior, which is regulated on simultaneous different time scales, aims and projects, and admits suspension, deferral and rescheduling of the various behaviors and projects, conciliation and compromise. The role of multimodal associative areas is not less important in parietal, occipital and temporal regions, where they sustain most cognitive, mnemonic, logic and linguistic activities. More generally, as we shall see, the degree of vigilance and conscience is a function, in man, of the intensity of neuronal activity in multimodal associative areas.