THE BASIC BRAIN MATTER

[The following is a long section from E.O. Wilson's book CONSILIENCE. It reflects to me explanations from many other books I've recently read, such as LeDoux's The Synaptic Self, Pinker's How the Mind Works, La Cerra's The Origin of Minds and, finally, McCone's Going Inside; a tour around a moment of consciousness. I'm a novice, but, if you ask me, what is included in this passage from Wilson's book is what we novice's want to know about the evolution of mind. It specially struck up memories of McCone's Going Inside. Anyhow, take your time and read it. Copy it out and study it. To understand this passage is to understand that there just can't be no god thing nowhere, nohow, notime out there anywhere.]

from CONSILIENCE by biologist E.O. Wilson (pp. 106-115):

WHAT MORE CAN be said of brain structure? If a Divine Engineer designed it, unconstrained by humanity’s biological history, He might have chosen mortal but angelic beings cast in His own image. They would presumably be rational, far-seeing, wise, benevolent, unrebellious, selfless, and guilt-free, and, as such, ready-made stewards of the beautiful planet bequeathed them. But we are nothing like that. We have original sin, which makes us better than angels. Whatever good we possess we have earned, during a long and arduous evolutionary history. The human brain bears the stamp of 400 million years of trial and error, traceable by fossils and molecular homology in nearly unbroken sequence from fish to amphibian to reptile to primitive mammal to our immediate primate forerunners. In the final step the brain was catapulted to a radically new level, equipped for language and culture. Because of its ancient pedigree, however, it could not be planted like a new computer into an empty cranial space. The old brain had been assembled there as a vehicle of instinct, and remained vital from one heartbeat to the next as new parts were added. The new brain had to be jury-rigged in steps within and around the old brain. Otherwise the organism could not have survived generation by generation. The result was human nature: genius animated with animal craftiness and emotion, combining the passion of politics and art with rationality, to create a new instrument of survival.

Brain scientists have vindicated the evolutionary view of mind. They have established that passion is inseverably linked to reason. Emotion is not just a perturbation of reason but a vital part of it. This chimeric quality of the mind is what makes it so elusive. The hardest task of brain scientists is to explain the products-tested engineering of the cortical circuits against the background of the species’ deep history. Beyond the elements of gross anatomy I have just summarized, the hypothetical role of Divine Engineer is not open to them. Unable to deduce from first principles the optimum balance of instinct and reason, they must ferret out the location and function of the brain’s governing circuits one by one. Progress is measured by piecemeal discoveries and cautious inferences. Here are a few of the most important made by researchers to date:

• The human brain preserves the three primitive divisions found throughout the vertebrates from fishes to mammals: hindbrain, midbrain, and forebrain. The first two together, referred to as the brain stem, form the swollen posthead on which the massively enlarged forebrain rests.

• The hindbrain comprises in turn the pons, medulla, and cerebellum. Together they regulate breathing, heartbeat, and coordination of body movements. The midbrain controls sleep and arousal. It also partly regulates auditory reflexes and perception.

• A major part of the forebrain is composed of the limbic system, the master traffic-control complex that regulates emotional response as well as the integration and transfer of sensory information. Its key centers are the amygdala (emotion), hippocampus (memory, especially short-term memory), hypothalamus (memory, temperature control, sexual drive, hunger, and thirst), and thalamus (awareness of temperature and all other senses except smell, awareness of pain, and the mediation of some processes of memory).

• The forebrain also includes the cerebral cortex, which has grown and expanded during evolution to cover the rest of the brain. As the primary seat of consciousness, it stores and collates information from the senses. It also directs voluntary motor activity and integrates higher functions, including speech and motivation.

• The key functions of the three successive divisions—hind- plus midbrain, limbic system, and cerebral cortex—can be neatly summarized in this sequence: heartbeat, heartstrings, heartless.

• No single part of the forebrain is the site of conscious experience. Higher levels of mental activity sweep through circuits that embrace a large part of the forebrain. When we see and speak of color, for example, visual information passes from the cones and interneurons of the retina through the thalamus to the visual cortex at the rear of the brain. After the information is codified and integrated anew at each step, through patterns of neuron firing, it then spreads forward to the speech centers of the lateral cortex. As a result, we first see red and then say “red.” Thinking about the phenomenon consists of adding more and more connections of pattern and meaning, and thus activating additional areas of the brain. The more novel and complicated the connections, the greater the amount of this spreading activation. The better the connections are learned by such experience, the more they are put on autopilot. When the same stimulus is applied later, new activation is diminished and the circuits are more predictable. The procedure becomes a “habit.” In one such inferred pathway of memory formation, sensory information is conveyed from the cerebral cortex to the amygdala and hippocampus, then to the thalamus, then to the prefrontal cortex (just behind the brow), and back to the original sensory regions of the cortex for storage. Along the way codes are interpreted and altered according to inputs from other parts of the brain.

• Because of the microscopic size of the nerve cells, a large amount of circuitry can be packed into a very small space. The hypothalamus, a major relay and control center at the base of the brain, is about the size of a lima bean. (The nervous systems of animals are even more impressively miniaturized. The entire brains of gnats and other extremely small insects, which carry instructions for a series of complex instinctive acts, from flight to mating, are barely visible to the naked eye.)

• Disturbance of particular circuits of the human brain often produce bizarre results. Injuries to certain sites of the undersurface of the parietal and occipital lobes, which occupy the side and rear of the cerebral cortex, cause the rare condition called prosopagnosia. The patient can no longer recognize other persons by their faces, but he can still remember them by their voices. Just as oddly, he retains the ability to recognize objects other than faces by sight alone.

• There may be centers in the brain that are especially active in the organization and perception of free will. One appears to be located within or at least close to the anterior cingulate sulcus, on the inside of a fold of the cerebral cortex. Patients who have sustained damage to the region lose initiative and concern for their own welfare. From one moment to the next they focus on nothing in particular, yet remain capable of reasoned responses when pressed.

• Other complex mental operations, while engaging regions over large parts of the brain, are vulnerable to localized perturbation. Patients with temporal lobe epilepsy often develop hyperreligiosity, the tendency to charge all events, large and small, with cosmic significance. They are also prone to hypergraphia, a compulsion to express their visions in an undisciplined stream of poems, letters, or stories.

• The neural pathways used in sensory integration are also highly specialized. When subjects name pictures of animals during PET (positron emission tomography) imaging, a method that reveals patterns of nerve-cell firing, their visual cortices light up in the same pattern seen when they sort out subtle differences in the appearance of objects. When, on the other hand, they silently name pictures of tools, neural activity shifts to parts of the cortex concerned with hand movements and action words, such as “write” for pencil.

I HAVE S P0 K E N so far about the physical processes that produce the mind. Now, to come to the heart of the matter, what is the mind? Brain scientists understandably dance around this question. Wisely, they rarely commit themselves to a simple declarative definition, Most believe that the fundamental properties of the elements responsible for mind—neurons neurotransmitters, and hormones—are reasonably well known. What is lacking is a sufficient grasp of the emergent, holistic properties of the neuron circuits, and of cognition, the way the circuits process information to create perception and knowledge. Although dispatches from the research front grow yearly in number and sophistication, it is hard to judge how much we know in comparison with what we need to know in order to create a powerful and enduring theory of mind production by the brain. The grand synthesis could come quickly, or it could come with painful slowness over a period of decades.

Still, the experts cannot resist speculation on the essential nature of mind. While it is very risky to speak of consensus, and while I have no great trust in my own biases as interpreter, I believe I have been able to piece together enough of their overlapping opinions to forecast a probable outline of the eventual theory, as follows.

Mind is a stream of conscious and subconscious experience. It is at root the coded representation of sensory impressions and the memory and imagination of sensory impressions. The information composing it is most likely sorted and retrieved by vector coding, which denotes direction and magnitude. For example, a particular taste might be partly classified by the combined activity of nerve cells responding to different degrees of sweetness, saltiness, and sourness. If the brain were designed to distinguish ten increments in each of these taste dimensions, the coding could discriminate 10 X 10 X 10, or 1,000 substances.

Consciousness consists of the parallel processing of vast numbers of such coding networks. Many are linked by the synchronized firing of the nerve cells at forty cycles per second, allowing the simultaneous internal mapping of multiple sensory impressions. Some of the impressions are real, fed by ongoing stimulation from outside the nervous system, while others are recalled from the memory banks of the cortex. All together they create scenarios that flow realistically back and forth through time. The scenarios are a virtual reality. They can either closely match pieces of the external world or depart indefinitely far from it. They re-create the past and cast up alternative futures that serve as choices for future thought and bodily action. The scenarios comprise dense and finely differentiated patterns in the brain circuits. When fully open to input from the outside, they correspond well to all the parts of the environment, including activity of the body parts, monitored by the sense organs.

Who or what within the brain monitors all this activity? No one. Nothing. The scenarios are not seen by some other part of the brain. They just are. Consciousness is the virtual world composed by the scenarios. There is not even a Cartesian theater, to use Daniel Dennett’s dismissive phrase, no single locus of the brain where the scenarios are played out in coherent form. Instead, there are interlacing patterns of neural activity within and among particular sites throughout the forebrain, from cerebral cortex to other specialized centers of cognition such as the thalamus, amygdala, and hippocampus. There is no single stream of consciousness in which all information is brought together by an executive ego. There are instead multiple streams of activity, some of which contribute momentarily to conscious thought and then phase out. Consciousness is the massive coupled aggregates of such participating circuits. The mind is a self-organizing republic of scenarios that individually germinate, grow, evolve, disappear, and occasionally linger to spawn additional thought and physical activity.

The neural circuits do not turn on and off like parts of an electrical grid. In many sectors of the forebrain at least, they are arranged in parallel relays stepping from one neuron level to the next, integrating more and more coded information with each step. The energy of light striking the retina, to expand the example I gave earlier, is transduced into patterns of neuron firing. The patterns are relayed through a sequence of intermediate neuron systems out of the retinal fields through the lateral geniculate nuclei of the thalamus back to the primary visual cortex at the rear of the brain. Cells in the visual cortex fed by the integrated stimuli sum up the information from different parts of the retina. They recognize and by their own pattern of firing specify spots or lines. Further systems of these higher-order cells integrate the information from multiple feeder cells to map the shape and movement of objects. In ways still not understood, this pattern is coupled with simultaneous input from other parts of the brain to create the full scenarios of consciousness. The biologist S. J. Singer has drily expressed the matter thus: I link, therefore I am.

Because just to generate consciousness requires an astronomically large population of cells, the brain is sharply limited in its capacity to create and hold complex moving imagery. A key measure of that capacity lies in the distinction made by psychologists between short-term and long-term memory. Short-term memory is the ready state of the conscious mind. It composes all of the current and remembered parts of the virtual scenarios. It can handle only about seven words or other symbols simultaneously. The brain takes about one second to scan these symbols fully, and it forgets most of the information within thirty seconds. Long-term memory takes much longer to acquire, but it has an almost unlimited capacity, and a large fraction of it is retained for life. By spreading activation, the conscious mind summons information from the store of long-term memory and holds it for a brief interval in short-term memory. During this time it processes the information, at a rate of about one symbol per 25 milliseconds, while scenarios arising from the information compete for dominance.

Long-term memory recalls specific events by drawing particular persons, objects, and actions into the conscious mind through a time sequence. For example, it easily re-creates an Olympic moment: the lighting of the torch, a running athlete, the cheering of the crowd. It also re-creates not just moving images and sound but meaning in the form of linked concepts simultaneously experienced. Fire is connected to hot, red, dangerous, cooked, the passion of sex, and the creative act, and on out through multitudinous hypertext pathways selected by context, sometimes building new associations in memory for future recall. The concepts are the nodes or reference points in long-term memory. Many are labeled by words in ordinary language, but others are not. Recall of images from the long-term banks with little or no linkage is just memory. Recall with linkages, and especially when tinged by the resonance of emotional circuits, is remembrance.

The capacity for remembrance by the manipulation of symbols is a transcendent achievement for an organic machine. It has authored all of culture. But it still falls far short of the demands placed by the body on the nervous system. Hundreds of organs must be regulated continuously and precisely; any serious perturbation is followed by illness or death. A heart forgetful for ten seconds can drop you like a stone. The proper functioning of the organs is under the control of hard-wired autopilots in the brain and spinal cord, whose neuron circuits are our inheritance from hundreds of millions of years of vertebrate evolution prior to the origin of human consciousness. The autopilot circuits are shorter and simpler than those of the higher cerebral centers and only marginally communicate with them. Only by intense meditative training can they occasionally be brought under conscious control.

Under automatic control, and specifically through balance of the antagonistic elements of the autonomic nervous system, pupils of the eye constrict or dilate, saliva pours out or is contained, the stomach churns or quietens, the heart pounds or calms, and so on through alternative states in all the organs. The sympathetic nerves of the autonomic nervous system pump the body up for action. They arise from the middle sections of the spinal cord, and typically regulate target organs by release of the neurotransmitter norepinephrine. The parasympathetic nerves relax the body as a whole while intensifying the processes of digestion. They rise from the brain stem and lowermost segment of the spinal cord, and the neurotransmitter they release to the target organs is acetylcholine—also the agent of sleep.

Reflexes are swift automatic responses mediated by short circuits of neurons through the spinal cord and lower brain. The most complex is the startle response, which prepares the body for an imminent blow or collision. Imagine that you are surprised by a loud noise close by—a car horn blasts, someone shouts, a dog charges in a fury of barking. You react without thinking. Your eyes close, your head sags, your mouth opens, your knees buckle slightly. All are reactions that prepare you for the violent contact that might follow an instant later. The startle response occurs in a split second, faster than the conscious mind can follow, faster than can be imitated by conscious effort even with long practice.

Automatic responses, true to their primal role, are relatively impervious to the conscious will. This principle of archaism extends even to the facial expressions that communicate emotion. A spontaneous and genuine smile, which originates in the limbic system and is emotion-driven, is unmistakable to the practiced observer. A contrived smile is constructed from the conscious processes of the cerebrum and is betrayed by telltale nuances: a slightly different configuration of facial muscle contraction and a tendency toward lopsidedness of the upward curving mouth. A natural smile can be closely imitated by an experienced actor. It can also be evoked by artificially inducing the appropriate emotion—the basic technique of method acting. In ordinary usage it is modified deliberately in accordance with local culture, to convey irony (the pursed smile), restrained politeness (the thin smile), threat (the wolfish smile), and other refined presentations of self.

Much of the input to the brain does not come from the outside world but from internal body sensors that monitor the state of respiration, heartbeat, digestion, and other physiological activities. The flood of “gut feeling” that results is blended with rational thought, feeding it, and being fed by it through reflexes of internal organs and neurohormonal loops.

As the scenarios of consciousness fly by, driven by stimuli and drawing upon memories of prior scenarios, they are weighted and modified by emotion. What is emotion? It is the modification of neural activity that animates and focuses mental activity. It is created by physiological activity that selects certain streams of information over others, shifting the body and mind to higher or lower degrees of activity, agitating the circuits that create scenarios, and selecting ones that end in certain ways. The winning scenarios are those that match goals preprogrammed by instinct and the satisfactions of prior experience. Current experience and memory continually perturb the states of mind and body. By thought and action the states are then moved backward to the original condition or forward to conditions conceived in new scenarios. The dynamism of the process provokes labeling by words that denote the basic categories of emotion—anger, disgust, fear, pleasure, surprise. It breaks the categories into many degrees and joins them to create myriad subtle compounds. Thus we experience feelings that are variously weak, strong, mixed, and new.

Without the stimulus and guidance of emotion, rational thought slows and disintegrates. The rational mind does not float above the irrational it cannot free itself to engage in pure reason. There are pure theorems in mathematics but no pure thoughts that discover them. In the brain-in-the-vat fantasy of neurobiological theory and science fiction, the organ in its nutrient bath has been detached from the impediments of the body and liberated to explore the inner universe of the mind. But that is not what would ensue in reality. All the evidence from the brain sciences points in the opposite direction, to a waiting coffin-bound hell of the wakened dead, where the remembered and imagined world decays until chaos mercifully grants oblivion.

Consciousness satisfies emotion by the physical actions it selects in the midst of turbulent sensation. It is the specialized part of the mind that creates and sorts scenarios, the means by which the future is guessed and courses of action chosen. Consciousness is not a remote command center but part of the system, intimately wired to all the neural and hormonal circuits regulating physiology. Consciousness acts and reacts to achieve a dynamic steady state. It perturbs the body in precise ways with each changing circumstance, as required for well-being and response to opportunity, and helps return it to the original condition when challenge and opportunity have been met.

The reciprocity of mind and body can be visualized in the following scenario, which I have adapted from an account by the neurologist Antonio R. Damasio. Imagine that you are strolling along a deserted city street at night. Your reverie is interrupted by quick footsteps drawing close behind. Your brain focuses instantly and churns out alternative scenarios—ignore, freeze, turn and confront, or escape. The last scenario prevails and you act. You run toward a lighted storefront further down the street. In the space of a few seconds, the conscious response triggers automatic changes in your physiology.

The catecholamine hormones epinephrine (“adrenaline”) and norepinephrine pour into the bloodstream from the adrenal medulla and travel to all parts of the body, increasing the basal metabolic rate, breaking down glycogen in the liver and skeletal muscles to glucose for a quick energy feed. The heart races. The bronchioles of the lungs dilate to admit more air. Digestion slows. The bladder and colon prepare to void their contents, disencumbering the body to prepare for violent action and possible injury.

A few seconds more pass. Time slows in the crisis: The event span seems like minutes. Signals arising from all the changes are relayed back to the brain by more nerve fibers and the rise of hormone titers in the bloodstream. As further seconds tick away, the body and brain shift together in precisely programmed ways. Emotional circuits of the limbic system kick in—the new scenarios flooding the mind are charged with fright, then anger that sharply focuses the attention of the cerebral cortex, closing out all other thought not relevant to immediate survival.

The storefront is reached, the race won. People are inside, the pursuer is gone. Was the follower really in pursuit? No matter. The republic of bodily systems, informed by reassuring signals from the conscious brain, begins its slow stand-down to the original calm state.

Damasio, in depicting the mind holistically in such episodes, has suggested the existence of two broad categories of emotion. The first, primary emotion, comprises the responses ordinarily called inborn or instinctive. Primary emotion requires little conscious activity beyond the recognition of certain elementary stimuli, the kind that students of instinctive behavior in animals call releasers—they are said to “release” the preprogrammed behavior. For human beings such stimuli include sexual enticement, loud noises, the sudden appearance of large shapes, the writhing movements of snakes or serpentine objects, and the particular configurations of pain associated with heart attacks or broken bones. The primary emotions have been passed down with little change from the vertebrate forebears of the human line. They are activated by circuits of the limbic system, among which the amygdala appears to be the master integrating and relay center.

Secondary emotions arise from personalized events of life. To meet an old friend, fall in love, win a promotion, or suffer an insult is to fire the limbic circuits of primary emotion, but only after the highest integrative processes of the cerebral cortex have been engaged. We must know who is friend or enemy, and why they are behaving a certain way. By this interpretation, the emperor’s rage and poet’s rapture are cultural elaborations retrofitted to the same machinery that drives the prehuman primates. Nature, Damasio observes, “with its tinkerish knack for economy, did not select independent mechanisms for expressing primary and secondary emotions. It simply allowed secondary emotions to be expressed by the same channel already prepared to convey primary emotions.”

Ordinary words used to denote emotion and other processes of mental activity make only a crude fit to the models used by the brain scientists in their attempts at rigorous explanation. But the ordinary and conventional conceptions—what some philosophers call folk psychology—are necessary if we are to make better sense of thousands of years of literate history, and thereby join the cultures of the past with those of the future. To that end I offer the following neuroscience-accented definitions of several of the most important concepts of mental activity.

What we call meaning is the linkage among the neural networks created by the spreading excitation that enlarges imagery and engages emotion. The competitive selection among scenarios is what we call decision making. The outcome, in terms of the match of the winning scenario to instinctive or learned favorable states, sets the kind and intensity of subsequent emotion. The persistent form and intensity of emotions is called mood. The ability of the brain to generate novel scenarios and settle on the most effective among them is called creativity. The persistent production of scenarios lacking reality and survival value is called insanity.

The explicit material constructions I have put upon mental life will be disputed by some brain scientists, and reckoned inadequate by others. That is the unavoidable fate of synthesis. In choosing certain hypotheses over others, I have tried to serve as an honest broker searching for the gravitational center of opinion, where by and large the supporting data are most persuasive and mutually consistent. To include all models and hypotheses deserving respect in this tumultuous discipline, and then to clarify the distinctions among them, would require a full-dress textbook. Undoubtedly events will prove that in places I chose badly. For that eventuality I apologize now to the slighted scientists, a concession I comfortably make, knowing that the recognition they deserve and will inevitably receive cannot be blunted by premature omission on the part of any one observer.