How does consciousness arise? What causes mind? What are the unique neurological processes of the human brain?
DNA, transactions, biochemistry, neurology, higher cortex, stimulus and response, reflex, sensation, receptors, learning.
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4.1 Mind, Brain, and Consciousness
"These are the central questions that the great philosopher David Hume said are of unspeakable importance: How does the mind work, and beyond that why does it work in such a way and not another, and from these two considerations together what is man's ultimate nature?" E O Wilson
"What in the soul is a passion in the body commonly speaking an action; so that there is no better means of arriving at a knowledge of our passions than to examine the difference which exists between soul and body in order to know to which of the two we must attribute each one of the functions within us." Descartes
"It follows that our mental conditions are simply the symbols in consciousness of the changes which take place automatically in the organism; and that, to take an extreme illustration, the feeling we call volition is not the cause of a voluntary act, but the symbol of that state of the brain which is the immediate cause of this act." T H Huxley
"What, in fact, is the alternative to this through-and-through Darwinian vision of the mind? A last hope for the Darwin-dreaders is simply to deny that what happens to memes when they enter the mind could ever, ever be explained in "reductionistic, mechanistic terms. One way would be to espouse outright Cartesian dualism: the mind just can't be the brain... " Daniel Dennett
"We are now in a position to compare the gradual increase through evolutionary time of both the amount of information contained in the genetic material and the amount of information contained in the brains of organisms. The two curves cross at a time corresponding to a few hundred million years ago... Much of the history of life since the Carboniferous Period can be described as the gradual... dominance of brains over genes." Carl Sagan.
"What a waste it is to lose one's mind. Or not to have a mind is being very wasteful. How true that is." Dan Quayle
"Loosing Our Minds to Darwin" Chapter heading of Dennett
4.1.1 How Brains Work
In the Theory of Options we view all human biology as an integrated whole, each part balanced with every other. The relationship of the human hand to the foot say, is a special optimization of function, where four general purpose primate limbs have become optimized into two sets of limbs, one for locomotion and one for manipulation. Many parts of human anatomy form this same optimization. If the new theory is accepted it is hoped that experts will restudy all human anatomy from this perspective to explain it in optimization of function terms.
Even so, the new theory will not be accepted because evolutionary design of the human hand, foot, eye, or face could not be explained any other way. Instead, the most unique of all human anatomical features, the human brain, has become the enabling technology of humanity's shift from its mode of biological to cultural evolution. And it was not just any brain. It was a brain rich with the learning neural circuits of the higher cortex. Specialized reflex neural circuits existed for hundreds of millions of years, but these are costly designs in evolutionary time and effort. Yet when they had been designed once, and all vertebrates but especially higher mammals have them, learning circuits could be multiplied millions of times over for effect. This expediency of evolutionary design is important for two reasons.
- Through learning and cultural evolution, it allows the species an alternative to the biological struggle to adapt.
- Through the highly flexible circuits of the higher cortex learning allows a breaking the physical chain of cause-and-effect inherent in reflexive thinking. This allows humans such novel thought modes as imagination, abstraction, reason and moral feelings.
But how do brains work? We say that humans possess intelligence, but what is that? Human brains evolved by natural selection. But if the outstanding feature of the human brain, its learning circuits, is just a multiplied effect of an attribute evolved in more primitive brains what makes the human brain unique? The Theory of Options teaches that the human brain is optimized for versatility and intelligence, but how do we know this? The brain remains a great puzzle of human evolution so what can the new theory tell us about the brain, which other theories cannot?
Broadly, a brain is a physical, anatomical entity that does three things.
- It centralizes and coordinates nervous functions (a nerve center) much as a telephone exchange might.
- It registers a reaction we call sensation, giving rise to consciousness.
- It gathers information and makes responses.
All these attributes evolved, and brains, as opposed to just nervous systems did not exist even anatomically until forms of sensation and organized response to stimulus evolved. Microscopic and primitive organisms and plants generally do not register sensation, even if some organisms possess a primitive nervous system. But as the available niches for organisms become filled newer organisms are forced to become mobile, actively seeking nourishment and reproduction. Once obtaining mobility however, organisms encounter a range of effects to which the organism must know how to respond. Rather than program the organism with a response for every effect, it is more efficient to group effects together, such that "this group is harmful" or "this group is beneficial". Sensation gives groups of effects immediate identification by labeling a harmful group with sentient awareness of "pain". This allows a general response such as; "always avoid pain" or "seek things which are pleasurable". This is crucial as organisms became larger, when a large outer surface area might need to react to temperature, texture, or impact. Rather than assign a complex neural response for each nerve receptor on the skin surface, it is efficient design to route the receptor information to a central area classifying incoming signals as a category of sensation, which other circuits would be programmed to respond to.
Use of sensation is not only more efficient design, it increases options of behavior. Without sensation the response is fixed. The receptors receive an input, it is processed by dedicated inter-neurons and motor nerves respond with a muscle twitch. But sensation provides additional steps. The receptor nerves send a signal to the inter-neurons, but while these might respond with a direct signal to motor nerves they also send additional signals to a further set of inter-neurons, stimulating sensation. This sensation in turn becomes an impetus to further inter-neurons, which then might send a signal to the motor neurons for a muscular response. The advantage is that the brain can receive several signals producing sensation and evaluate them comparatively for a best response. An organism say, can be programmed to both seek food and conserve energy, but without sensation it cannot evaluate which response optimizes the opportunity latent in any situation. So, if seeking food is registered as a sensation, and so is conserving energy, this will allow an opportune behavior of seeking food in ways that conserve energy, evaluated by motive.
With behavior driven by motive, rather than direct autonomic reflex, organisms can adjust needs for food, procreation, conserving energy and avoiding danger to the overriding motive of a situation. If an organism faces too great a danger competing for mates it can opt to conserve energy and attempt procreation at a more opportune time. Balancing motives this way rather than responding instinctively broadens the range of selective factors operating on individuals, and speeds up evolution. If an organisms faces danger seeking its usual food source it might expend extra energy to seek an alternative source. Organisms that do not have brains also experiment with alternative food sources, only they do it the hard way by individuals who do not make it going extinct. This requires much longer evolutionary time to evolve variation. Extinction is the selection mechanism among organisms with brains as well, only with brains extinction can select among a greater range of attributes because it can weed out inopportune behaviors rather than just selecting out less specialized designs. This increases rate of variation, which is a fitness advantage in changing environments.
4.1.2 Reflex and Learning
But brains do not just evaluate responses. They gather information. Without visual or audio inputs information gathering and sentient response are not so different. But over evolutionary time pleasure of light and fear or elation at movement produced a new form of sensation. This occurs when light and movement awareness produces sensation as information only, without direct motive of "pain" or "pleasure". This higher form of awareness manifested as vision, and later hearing, allows the development of consciousness. This is awareness of the world in a more orderly form. Once evolved visual or audio consciousness allows organisms to register sensations that inform rather than compel. Movement of a large animal might compel flight as reflex, but with consciousness an organism can evaluate if this particular situation does require flight, or if it is safe to stay and gather more food. This will increase options of when to rest or expend energy, and increases behavioral opportunities.
Yet for all the advantages both sentience and consciousness offer, nature never abandons the non-sentient autonomic response system. Instead, in the design of any brain (including hominid brains - see diagram) evolution builds layers of sentient response on top of the non-sentient system, such that organisms with consciousness experience two forms of response. One is the primal, autonomic muscle twitch response independent of sensation. The other is the sentient response, in which motor neurons, rather than responding with a muscle twitch, produce sensation, which by its power motivates the organism to move the muscles it consciously controls in certain behaviors.
In medical terminology any effect producing a response in an organism is called a stimulus, while the process of stimulus-response, without the intermediary of sensation is called reflex. But in philosophy stimulus refers to effects producing sensation, while either sentient or non-sentient responses, providing they are automatic are lumped together as reflex. The distinction is important for the next stage of evolution, which not all brains achieve; evolution of mind. Mind occurs when a brain can experience sensation without direct stimulus. In any brain all sensations, even those from stimulus, are only the body's biochemistry acting on consciousness. But as organisms become more complex nature utilizes the body's biochemistry to create new sensations acting on sentience as mood, affection or emotion, but without direct stimulation. The affection "fear" say, is an abstraction of the sensation "pain", so that a higher organism can experience fear, without direct stimulation of pain. The evolutionary advantage to this is that "fear" will motivate an organism to avoid situations causing "pain", plus emotions help organisms evaluate complex situations where direct stimulus might provide conflicting signals, such as sighting food and danger together. Emotions like fear play a further reflexive role such as heightening the body's preparedness to deal with danger by pumping adrenaline into the blood stream.
Finally, while we regard consciousness as being in a state of awareness when awake, sensation without stimulation, as occurs in mind, can produce mental processes when the brain is asleep, or unconscious. Because all higher mammals dream, learn, remember, and experience emotion, they possess mind, though critics might argue that only humans truly possess mind in its connoted sense. Just we should not become mystical over the meaning of mind. Anatomically it is another layer of neurology built up over the more primitive brain layers. So there are several layers altogether. There is the non-sentient autonomic system, the sentient response system, visual, audio and information gathering response systems, and finally, the topmost layer composes the more complex circuits of mind.
Yet, if mind is so important that only some brains evolve it, what is the enabling technology that makes mind possible?
It is those attributes referred to in this book as learning circuits, and is very important. The first neural circuits to evolve are for reflex, which we say has a fixed wiring diagram. Wiring is a poor term in that it is more like tubing than wiring, but bear with the metaphor. These fixed, reflexive neural circuits are ones in which axons connect to neurons in specific patterns encoded in the genes. Thus, the connection pattern was developed slowly by evolutionary selection of winning designs. (See diagram of typical reflexive circuits.) On the other hand learning circuits are not coded hardwired. Instead, much of the connection is made after birth. The genes encode messages not of how to wire circuits to a specific pattern, but instructions about how to wire up, test, and modify a neural circuit on the fly depending on stimulus. The evolutionary advantage of this is that whereas a thousand distinct reflex circuits would require a thousand separate instructions of how to wire them, a leaning circuit would only require one instruction how to wire it, and another instruction of say, how to reproduce this one pattern many times.
In this sense, learning circuits solve two evolutionary problems at once.
- They allow a much more flexible neurology allowing customization to circumstance, the way modern software can be customized to specific needs.
- Despite producing a more complex brain, learning circuits limit the number of genetic instructions that must be passed on to design a brain. This becomes crucial as the "bits" of complexity needed for brains exceed the "bits" of information which can be reasonably encoded in genes.
This problem of number of instructions is illustrated in the graph attached. This hypothesis was popularized by Carl Sagan in the "Dragons of Eden", but Sagan never followed his argument through. The estimated crossover point is 3 billion bits of information, which can be transmitted by genes, the amount of information a reptile needs in its brain. Mammals radiated 65 million years ago with a more complex, energetic brain than available to reptiles, requiring about 100 billion bits of information for a small mammalian brain. So, 65 million years ago evolutionary niches of creatures who could survive with a brain whose neural circuits could be completely specified genetically were already filled. With genetic code already saturated with instructions of how to wire a brain, nature began selecting for creatures that could multiply their most versatile reflex circuit many times. After this creatures using learning multiplied.
Very earlier, embryonic vertebrate brains are three small bulges in a row, like a match with three heads in a row. We call the topmost bulge the forebrain, the middle bulge is the midbrain, and the first bulge the hindbrain. We must presume that the very first brain was a single bulge, and this mutated to one extra bulge, then into one more. In a fish the hindbrain handles movement, the midbrain handles vision and the forebrain smell. Movement, vision and smell were possibly the evolutionary sequence by which these needs first evolved. Also it seems the deeper brain has most of its wiring fixed at birth, but the forebrain possibly always had some "loose" wires at birth, which could be modified by early learning. From that point forward different parts of the brain began to evolve at different rates. In humans, the midbrain remains tiny, with about 5% of neural bulk. The hindbrain is the next massive with about 15% neural bulk, while the forebrain completely dominates with some 80% of all neural bulk.
As the brain evolves different parts of the brain take over different functions. Learning neurology is flexible. It can acquire new skills in short evolutionary time plus it can quickly increase brain bulk by allowing the final wiring of the extra circuits after birth by learning. On the other hand reflex circuits are more reliable, and might act faster, as they do in computers. Except each new reflex circuit must be carefully refined by selection, which is a slow, costly build up in evolutionary time. Nature, like the computer engineer, must strike a balance between cost, flexibility, speed and reliability over the functions the brain must perform. For example, in early land vertebrates leaning how to walk the first time was done in the forebrain, which is the most flexible, advanced segment of the neurology with the highest concentration of learning circuits. But as walking became increasingly reflexive its basic coordination has been transferred to the hindbrain, leaving the forebrain free for other important things to learn.
Humans too now have a large hindbrain for complex reflexive tasks like muscle coordination in support of walking upright. Some 11% of human brain bulk is in this outgrowth of the hindbrain called the cerebellum. Possibly, early upright walking was focused first in the forebrain, but later shifted to the hindbrain as upright stance became reflexive in humans. Like in early computers, many novel tasks were first performed by the software. But as tasks became universal to all computer programs, it became more reliable and efficient to move these tasks into hardware. For example, 3-D visualization was first done only in software. But as all programs start to require it, this function is now being moved to hardware. Only the human cerebellum is not totally hardware either. Although the hindbrain is more fixed than the forebrain, the cerebellum expanded too quickly in human evolution to have totally fixed neurology. So most of its wiring is completed shortly after birth, though the embryonic hindbrain is totally wired at birth. On the other hand, only basic reflex such as balance or muscle coordination is concentrated in the hindbrain. Athletic skills such as whether one is a good swimmer, are focused in the forebrain where they can be perfected for many years after birth and stay adaptable to circumstance. Again, nature is leveraging that once the learning circuit type is perfected, it can be expanded in brain bulk more rapidly than it would take to select each individual circuit to be perfectly wired at birth. This can be used to expand brain bulk rapidly, while keeping new behaviors flexible through learning after birth.
The process of shifting skills from the fixed circuits of the lower brain to the learning skills of the higher brain is known as encephalization. Only we see that it is a two-way process. Not only are advanced skills moved into more bountiful and flexible learning neurology, but long established, essential skills are slowly refined into hardwired reflex. There are many evolutionary advantages to encephalization. One is that behavior becomes more versatile when relocated to learning circuits. The next advantage concerns genetic instructions. Because learning circuits have an essentially similar design, they can be multiplied in great quantities from much fewer genetic instructions than would be required to design and produce individual circuits of reflex. This allows a greatly expanded brain, from adding only a few genetic instructions. Only as we emphasize encephalization of functions once controlled by reflex allows increased specialization of the remaining reflex circuits. Although encephalization allows less functional reflex the total number of reflex genetic instructions will not go down. Instead, instructions of how to design reflex circuits will be redirected to refining the design of essential reflex, such as vision, metabolism, balance, reproduction and so on.
So, we should not think of encephalization as just of the higher cortex gaining an increased role while the other brain sections remain static. The brain evolves as a unit, and it will pay nature to shift highly repeatable functions back to the lower brain, or refine the functions of the lower brain to specialize while evolving slowly autonomic functions that it does well. In mammals the hindbrain, especially the cerebellum has evolved to a large size over amphibians and reptiles. In early animals movement was directed from the forebrain. But autonomic controls for complex coordination were better refined as semi-reflex. In domesticated animals such as horses and dogs we cannot teach them muscle-coordinated movements wired into the hindbrain that those animals instinctively perform. Yet, humans can train animals to perform movements like jumping with enhanced coordination, and these enhancements are movements controlled from the higher cortex. Finally, in primates, but notably humans, a broad range of muscle coordinated behaviors such as running, fighting, swimming, throwing, jumping, vocalization and acrobatics are learned to a greater or lesser extent. Humans have a large hindbrain because they have many muscles and require complex autonomic control for muscle coordination in any skill. But volitional athletic movement is skill directed in humans from the higher cortex. Maps of the higher cortex show almost the total of it involved in behaviors we might have at first presumed to be reflex.
Some years ago there was a popular triune brain theory, by Richard MacLean. This proposed that the brain had three basic layers, though these layers did not strictly follow the embryonic forebrain, midbrain and hindbrain layers. Maclean's theory was that the inner brain is reptilian, next was the limbic system that was lower mammal, and the outer layer was the neo-cortex or higher mammal. It was an interesting theory, but the three tiered embryonic brain predates mammals, at least to the earliest vertebrates. Plus the brain evolves at least five or six anatomical layers in detail, and neural function evolves outwards as the brain develops across all the layers. Moreover, the physical emotions humans or higher mammals feel such as loneliness or embarrassment are released as physiology in the deeper brain, though such emotions are hardly reptilian. Rather, it seems that transactions leading to behaviors interact across all the brain layers, which evolved to meet those needs at the time. With encephalization especially, the absolute size of the brain's reflex does not go down but increases through refining autonomic controls such as those for highly coordinated actions. Particularly in humans, the relative size of the learning cortex goes up by a large amount.
4.1.4 Feelings and Emotion
Are there any more layers to the brain above learning? Or is learning itself differentiated into layers, at least in terms of circuit design?
Both birds and mammals use learning, but these split from a common reptilian-type ancestor over 300 million years ago. So, if learning circuits only evolved once they should be in the ancestor. We know mammals evolved smarter brains since then, but so did birds, and we are not sure if advanced learning circuits evolve separately in birds. Birds have a form of learning called mimicry or imprinting. This might have evolved separately from how learning circuits of mammals evolved, but it is equally likely that mimicry is a more primitive form of learning, evolved in the common ancestor. As we shall also see learning takes at least two forms physically. One is the wiring of the inter-neurons in ways that can be altered after birth, but there is also "memory" at a synaptic joint where wires are connected to other neurons. Synaptic or "memory" learning is probably very primitive, and already exists in purely reflexive brains like those of fish or reptiles. On the other hand, the common reptilian ancestor of birds and mammals might have evolved at least "wire once" learning circuits, which allow "one time" learning after birth by mimicry or imprinting. In this case there would also be in mammalian brains "wire once" learning circuits although it is not obvious what their exact modern functions is. Still, the unique learning circuit mammals possess is the "wire many times" one, which provides a capacity for learning out of all proportion to anything more primitive brains possess.
The other permutation to learning is what the learning circuits would be connected to. Learning circuits of a "wire once" or "wire many times" type will not allow much learning if they are only connected to fixed wiring reflex neurons. But once learning circuits are connected to each other, learning possibilities multiply rapidly. This is how the "wire many times" circuits might have evolved. In birds say, it seems that the "wire once" circuit can be triggered at different times in the bird's life, probably on an instruction from a fixed neural circuit. But once the "wire on command" neural circuit separated from the fixed circuit to become connected instead to another learning circuit, the learning process itself becomes more independent of the genetic instruction. Whatever the case, in human brains we get massive interconnection between "wire many times" learning circuits larger than any other form of neural connection. This allows for both thinking and learning which is reflective (rather than reflexive), to an extent of allowing 'learning about learning' and 'thinking about thinking' which has become the hallmark of our species. Significantly in all this, human DNA is only 1-2% different from chimp DNA. So, considering the other anatomical differences between chimps and humans, probably not much of the DNA variation goes into neural designs as such, apart from specifying a recipe of a huge number of interconnected "wire many times" neural learning circuits.
Only now we come to an attribute of learning circuits often overlooked. It has been described how sensation is a form of motor response existing in the lower brain, and so circuits producing sensation are available first before learning circuits evolve. Nature is an efficient designer, but especially with respect to neurology. So if circuits producing sensation already exist there would be no need to reinvent them once learning circuits arrived. This would be especially true if sensation circuits were hardwired reflex and saturation of genetic instructions for producing reflexive neural design caused learning to arise anyway. Also, as learning is a more versatile and advanced circuitry, nature is certain to build learning as one more 'layer' over the top existing structure, as it did in every other advance, utilizing at a lower level what was already there. This infers that even though learning circuits produce sensation, but especially more abstracted sensations of mood, temper, and affection, the learning circuits themselves are not inherently "sentient". Rather, the learning circuits of the upper cortex are tied through inter-neurons to those producing "sensation" in the lower brain. For example, in the human brain the thoughts of the higher cortex, the cerebrum, produce emotional responses in the limbic system, which is a lower earlier evolve layer. But physical response of muscle twitch or release of chemicals is possibly in lower, earlier evolved layers, such as the pons or thalamus.
This peculiarity of neurology of where the physical response is produced complicates how we explain emotions such as moral feelings, and how a person responds to behaviors acquired by learning. The process is;
- A stimulus enters through the more primitive brain,
- It moves up through brain layers to as high as learning, and provokes a learned response.
- This response triggers a sensation back in a primitive segment of the lower brain.
We will call the history of a stimulus impinging on the senses, until its final response in the motor circuits, a transaction. Now in primitive animals without learning transactions will be indistinguishable from reflex. We suppose that for two animals of the same genome, without learning;
- Identical stimulus will cause identical reflex
- Identical stimulus will cause identical transactions.
But for animals from the same genome but with learning;
- Identical stimulus will cause identical reflex
- Identical stimulus could cause different transactions.
Lion cubs raised in captivity must be re-taught to kill in the wild. So even for a wild cub and domesticated cub taken from the same litter identical stimulus could cause different responses, and hence different transactions. Just as in humans, violence might cause very different reactions in a soldier to a priest, and so on. Only with learning while the input reflex might be identical the output reflex might be different, depending on how learning circuits routed a learned segment of the transaction through the higher cortex. Thus, two individuals with learning might "feel" different moods from identical circumstances. This in turn complicates moral theory, when we examine why people 'react' in an allegedly programmed way to ideas or suggestions.
As encephalization evolves however, one more component of neural machinery is required, which we will call "transfer circuits". These supervise encephalization. They ensure that learning circuits, which are modifiable, work as reliably under stress as do the solid "hard-wired" circuits of reflex. Encephalization is an efficient strategy but it means transferring crucial behavioral functions to more recently evolved, self-learning circuits, whose phenotype behavior will not be directly controlled by the genotype. This will require one more circuit controlled by the genotype, to control the learning circuits. Little research has been done on this, so for now the existence of "transfer circuits" is only logically inferred. But if they do exist transfer circuits could more logically explain a genetic basis to moral feelings and leaning injunctions, than could other theories. We will return to this issue when we discuss theories of morality.
To summarize then, brain, mind, consciousness, intelligence, moods, and feelings are all complex phenomena, which need explanation. Yet, none of these are in any way metaphysical in that they cannot be explained in evolutionary terms. We see the brain building up anatomically in layers with each new evolutionary strategy, and each new layer bringing into existence new forms of consciousness.
Finally, as we shall see in the following chapters, evolutionary development of the brain plus philosophical theories of mind and intelligence need not stand in contradiction. Rather, we should use the evolution of the brain to verify a purely rational understanding of what mind, brain and consciousness is.
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