The Conscious Dimension

by Allan Chubb

Reductionist and Epiphenomenal Opinion

Reductionists base their conclusions about consciousness on the physical nature and functioning of the nervous system. They begin with a study of neuroanatomy and then progress to physiology, electrochemistry and biochemistry. Some of these fields are areas for the specialist but we can gain enough understanding of these subjects to understand why reductionists think the way they do. We will begin by looking at the gross anatomy of the brain. Remember that scientists view zoology from an evolutionary perspective. Look at Diagram 10 which shows the brains of a fish, amphibian, lizard, rabbit and man. This represents the evolutionary stages of the development of the brain. These diagrams are not to scale but it will be noted that the evolutionary trend has been for an increase in the size of the forebrain culminating with a very large human forebrain, or cerebrum.

Gross Neuroanatomy

It was thought at first that information in the brain was stored all over the cerebrum, very much like the way that a hologram stores information about one object in the picture with this information at every location on the hologram. Diagnostic experiments at Yerkes laboratory at Yale showed that this was not the case and that different areas in the cerebrum specialise in storing different kinds of information.There are, however, rich neural connections between these areas.

This is a good starting point, although it should be realised that in reality more than one discrete area is involved in a conscious activity such as vision. The most simple example is to locate which areas are active when you are consciously aware of a red light or a small red object such as a ball. We shall see, however, that tracking such a simple conscious event can prove difficult. It is not a simple event but more a process. Later we shall be considering memory. The hippocampus plays an important role in our memory functioning and research suggests it is important in enabling us to handle spatial relations and sequences of spacial relations. It also handles sequential relations of an auditory kind. In this way it is crucial to the correct functioning of memory.
Other parts of the brain are also important. The amygdala is important as it is involved in anger and fear. The awareness of pain is connected with the mid brain, the hind brain and the brain stem. In the mid brain we find the putamen. When you learn a motor skill such as walking, cycling or a racket sport, to name a few such skills, these are eventually delegated to the putamen and are then performed without our conscious involvement. Also involved in controlling such coordinated behaviours is the hind brain structure, the cerebellum, which is largely responsible for the integration and coordination of the neurones involved in such activities.

In the mid brain we find the thalamus and hypothalamus. The thalamus is the relay centre for nerves carrying information to and from the cerebral cortex. The hypothalamus, although a relatively small part of the brain, has an important role in regulating the amount of sugar in the blood and also calcium, potassium and phosphate levels. It is a homostatic regulator, controlling when we feel hungry, thirsty, sleepy, when we have a propensity for sexual activity, and is important in temperature control. In short, the hypothalamus functions as a kind of switch mechanism, although these activities do not function alone. They are integrated both by neural connections and hormonal control with other parts of the nervous system and body.

The sense organs connect to the relevant areas of the cerebrum. In the case of sight, hearing, smell and taste these go relatively directly. Although some information about touch and muscle tone is conveyed to the cerebrum by the facial nerves, most information about this is conveyed by relatively long nerves entering the spinal cord, passing dorsally up the cord to the thalamus and thence to the cerebrum. Information from the internal organs such as heart, lungs and gut, of which we are totally unaware, travels via the spinal cord to centres in the brain stem. However, some information about these functions does occasionally arrive at the brain as evidenced by pain in these areas, and awareness of psychosomatic problems.

The autonomic nervous system, which is beyond conscious control, is responsible for stimulating the reticular activating system (RAS) in the brain stem. It consists of two complimentary parts: the parasympathetic and the sympathetic system. The parasympathetic activity has the effect of slowing things down and conserving energy while the sympathetic system is the spend thrift of the body’s energy. It has been called the fight or flight system. Clearly most of the time it is better to be functioning on the parasympathetic system as this conserves energy and for the most part the mind and body are most effective in this state.

The RAS is located in the brain stem and, though a lowly centre, is of some importance since it controls the level of conscious awareness. It does this by sending a diffuse network of neurones to the cerebral cortex. When the RAS is little active we feel sleepy. As the activity of the RAS increases so does the level of attentiveness. This can vary from just being aware, to a relaxed state, to an attentive state, to a very alert state and sometimes to the ultimate state of hysteria; a very high state of RAS activity. It is important to remember that consciousness functions at various levels.

These are the gross anatomical structures of the nervous system of humans and their associated functions, but what about the role of the microstructure in the functioning of the nervous system and in consciousness? It is believed that the brain is the seat of consciousness and that the cerebrum plays a major role. Let us now look at the microstructure of the cerebrum.

Conduction of the Nerve Impulse

It must be stated at the outset that there are a vast number of different kinds of nerve cells in the cortex of the cerebrum which are organised into six layers, some being divided into sublayers. These layers are most highly organised in the human brain. However, we can grasp the basic functioning of neurones at the micro neurological level by considering how a simple reverberatory nerve circuit functions and is integrated.

First let us see how a single neurone conducts an impulse and how that information crosses the gap between neurones. The classical account of how the nerve conducts the electrical nerve impulse is based on the activity of the membrane of the neurone.

When the nerve cell is at rest, not conducting, the sodium ions (NA+) arrange themselves on the outside of the membrane and the potassium ions (P+) arrange themselves along the inside of the cell membrane. This creates an electrical potential across the membrane. There are tiny channels in the membrane which can allow an exchange of potassium and sodium ions. When the neurone is stimulated and conducts, a ripple passes along the neurone from the cell body towards the dendrites as sodium ions and potassium ions exchange places. However, as this takes place, the original situation of the sodium ions on the outside and the potassium ions on the inside is quickly restored. Whereas electricity in a wire could travel round the earth several times a second, this method of conduction is slow, being measured in metres per second. Some nerves conduct faster than others.

At best the conduction speed is only a metre or two a second. After this the nerve rests for a very brief period, known as the refractory period, then it can be stimulated again.

When the impulse reaches the end of the axon and dendrites, in order to trigger an impulse on the next nerve it must cross a small gap known as the synaptic gap. At the end of the dendrites is a swelling known as the synaptic bouton which contains a number of small vesicles in which are chemicals that can either activate or inhibit the activity of the next neurone as they abut onto the cell body. When the nerve impulse arrives at the synaptic bouton the vesicles are released into the synaptic cleft and this releases chemicals across the gap. On the cell body they either add an increment of excitation or inhibition to the cell body of the next neurone. It takes many of these synaptic clefts to stimulate the next cell to fire an action potential, and whether the next cell fires or not is computed electro-chemically from the relative amounts of excitory and inhibitory chemicals arriving on the membrane of the next cell body of the next neurone.

How the condition of the nerve impulse occurred was first studied in the squid giant axon. In invertebrates all nerves are unmyelinated and this has imposed a limit on the speed at which the nerve impulse can be conducted. In unmyelinated nerves the larger the cross section of the nerve the faster it can conduct. However this imposes a limit on invertebrates since it is obviously impractical for nerves to exceed a certain size.

Vertebrates have been able to achieve fast conduction and still keep the cross section of the nerve small by coating the axon with a myelin sheath. This has enabled some miniaturisation of the brain and peripheral nerves. Not all neurones in vertebrates are myelinated but most are.

Myelination of nerves enables a form of conduction known as saltary conduction, which is faster than conduction in the unmyelinated nerves previously described. The diagram shows a myelinated nerve and the nodes of Ranvier. In such nerves the nerve impulse does not ripple all the way down the axon but instead jumps from one node to the next, thereby speeding up conduction. This has been of great advantage to vertebrates and enabled their nervous systems to evolve to the present level.

This is the classical explanation of conduction in the nervous system. However, Sir Roger Penrose has suggested the interior structures in the neurone axon, known as microtubules, are involved. These are oriented along the length of the axon and contain chemicals which can exist in two quantum states. Normally the two states would be randomly arranged rather as molecules in an iron bar are arranged before becoming magnetic. This persists for a while and this persistence is known as coherence. Sir Roger Penrose suggests that when the nerve is stimulated these chemicals in the microtubule take on a particular quantum state and coherence is maintained sufficiently long to induce coherence in adjacent microtubules. Since every microtubule connects to six others and there are many of these along an axon it would result in a far greater number of computations taking place in the nerve affecting whether synaptic vesicles were released across the synaptic cleft or not. The best calculations concerning the computing power of the brain based on the classical theory that everything is achieved by conduction along the cell membrane and synaptic vesicles crossing the synaptic gap, is about 10/14 operations per second assuming 100% efficiency. Of course the brain never functions at 100% efficiency, but this figure is useful to compare with the estimate for efficiency if neural computation is achieved by the quantum state of the microtubules of the nerve cells. At 100% efficiency a comparable number of basic operations per second would be 10/27, putting it beyond any computational scheme. These two comparative estimates of operational power serve to show what the difference in functional capacity might be. Present estimates of the current potential capacity of Artificial Intelligence do not exceed 10/14. If the operation of the brain is achieved by using the microtubules then it is hard to see how Artificial Intelligence will ever be able to simulate the human brain. Besides, as JZ Young observes, the human brain does not function like a computer. Patrick Meredith has observed that the human brain is the most unpredictable piece of protoplasm.

Reverberatory Circuits

Having outlined the ideas about the way neurones conduct the nerve impulse it is now possible to consider the ways in which these neurones connect into circuits. Circuits of neurones, known as reverberatory circuits, are known to exist.

Since these reverberatory circuits are self-sustaining for a number of microseconds, reductionists believe that they form the neurological basis of unconscious and conscious awareness. These circuits arrange themselves into more complex systems, accounting for what D. O. Hebb describes as ‘The Organisation of Behaviour’.

It should be noted that there is a difference in the functions of the left and right hemispheres of the human brain. In the case of the left hemisphere the fatty myelin sheath continues well up the axon to the cell body. In the case of the axons in the right hemisphere there is a larger gap, allowing a greater number of synaptic connections. The result of this difference is that in a healthy brain the left hemisphere specialises in analytical processes such as mathematical calculations, whereas the right hemisphere is adept at recognising patterns and interpreting spatial relationships. In this way the various tasks are catered for.

Next we must consider how the memory functions at the synaptic cleft before considering the reductionist viewpoint further. Three types of memory are recognised: short term, intermediate and long term memory. The explanation of these is thought to be due to changes that take place at the synaptic junctions. Short term memory refers to things you can only retain in your mind for a short time. The classical illustration is to ask a person to try and remember a list of three lettered nonsense syllables such as ZOQ, JIR, TUX, WEG, and KIZ. People find that they can only retain such lists for a very short time. Scientists think that the chemical activity of the reverberatory circuit synapses account for this.

Intermediate term memory refers to some memories that last longer such as a day or more. Recording the day’s events in a diary is an example of this. If you leave writing up your diary for too long you may not be able to recall what happened on a particular day. The causes of this type of memory are more complex but it is known that there is what is termed plasticity at the junctions between nerves with some synaptic boutons swelling with use leading to increased vesicle release and sometimes even new synapses develop. These situations need not be permanent and can change with time. We have already seen that the region of the brain known as the hippocampus is important in intermediate memory.

Long term memory refers to things that you have remembered for a long time, maybe even from youth. It has been shown that in such cases actual chemical bridges of a relatively permanent nature form across the synaptic clefts.

There are now theories that DNA and RNA may be involved in memory so it would be more accurate to say that we do not really understand memory.

The Reductionist and Epiphenominal Position

Armed with this information we are now in a position to understand the basis for the reductionist view. The explanation of the brain in these terms has a long way to go and is the field of much current research. Such explanations are known as the search for the neurological correlate of consciousness (NCC). The true reductionist believes that consciousness is an illusion and that all decisions are taken electrochemically at the synaptic clefts. They believe that this is all controlled by the laws of physics and that in reality we do not possess free will.

Before passing on to modern trends in research on consciousness it is instructive to consider the history of the subject. Donald Hebb suggested that the reverberatory circuits through use came to overlap in a common experience and that they eventually formed larger reverberatory systems that represented impressions in the mind. The interplay of these more complex circuits represent our thinking. Eventually the activity of these systems arrive via the nerves at the muscles or glands causing activity, usually of the desired type. In babies and young infants we witness the gradual learning to coordinate muscle control such as eye/hand coordination and learning to grasp things. As time progresses the nature of the tasks undertaken becomes more complex as more reverberatory circuits become integrated and organised. Crawling, walking and running are examples of this.

The problem with Hebb’s idea is that it does not explain why some circuit systems should come to dominate others. An experiment by Tinbergen with a kite flown over some young ducklings in a roofless pen showed that these ducklings must have some kind of analysers built into their nervous systems. The kite is illustrated in the diagram below and it will be observed that if the kite is drawn in one direction it appears as the silhouette of a duck, but if pulled in the opposite direction as the silhouette of a hawk (a predator). In the experiment the ducklings, too young to have any experience of hawks or even duck silhouettes, ran for cover when the kite appeared as a hawk but did not do so when the kite appeared as a duck.

This led to a search for analysers in the nervous system which may account for a lot of the bias that develops in the organisation of behaviour. The implication is that the analysers are inherited as a result of evolution. Ducklings without such analysers could have disastrous ends. Psychologists are interested in finding which behaviours are inborn and which are developed. We shall be looking at this subject in more detail in the chapter on developmental psychology.

So far we have seen the basis for the thinking of the reductionist although it must be stated that the trend today is to recognise qualia. Qualia can be understood as the simplest basic units of perception or experience. The view of some reductionists is veering to what is known as integrated information theory. In the simplest form it involves areas of the brain, particularly the cerebral cortex, which are active during a qualia. In any given experience of the individual many qualia are active simultaneously, and somehow these must be integrated since healthy individuals report that their conscious experience at any time is a unity. As a result, although neuroscience finds qualia in various locations in the brain it is viewed that some holistic process is involved by which all these qualia are integrated into a unified experience, hence the term ‘integrated information theory’. Scientists are not sure that integrated information theory is correct but the search is on for such a solution.

How does this explain consciousness? Well conscious experience cannot be explained as such. The search is on for the Neurological Correlate of Consciousness (NCC). In this quest various channels are being explored. We have considered nerve networks and reverberatory circuits. Another field of investigation is the electronic field around the brain created by the brain’s activity. Can brain waves account for consciousness? Yet another approach is to investigate tissues which appear to be conscious and compare them with tissues known to be not conscious, even within the brain, and trying to trace chemicals likely to be involved to discover whether these chemicals charge up electronically. Even at the quantum level research proceeds to find the NCC’s. We shall see in the chapter on quantum theory that it may be important in explaining why we see conscious experience as a unity.

Not all scientists in this field view consciousness as an illusion. Already some neuroscientists are seeking an integrated information theory which recognises qualia. For many years there has been a group of scientist who take the epiphenominal view. These scientists view the same facts as reductionists and consider that decisions are taken electrochemically and so consider consciousness to be a dimension of electricity. This makes us think more carefully about what electricity really is.

We cannot leave the subject of reductionism and consciousness without mentioning the finger flexing experiment which reductionists claim to be of great significance. Quite a lot of investigation has been done into the timing of neural activity and the relationship to conscious awareness of those events. It should not surprise us that as far as sensory functioning is concerned consciousness is on the end of the line. Benjamin Libets’ experiments purport to show that in his finger flexing experiments conscious awareness of the decision to flex the finger lags behind the response by about half a second. Much theorising has been based on such experiments suggesting that free will is an illusion. This result is very controversial, as are the conjectures based upon it. We shall return to a discussion of this topic later in the book. However, one thing is true, and that is that our unconscious minds do a great deal of work for us. We may like to regard them as our servants.

In conclusion it must be said that not all philosophers would agree that electricity accounts for consciousness. John Lennox talks about the mindless chatter of electrical circuits. JZ Young, a neuroanatomist inclined towards the reductionist view, reminds us that we do not really know what thinking is. We are now in a position to understand those who take the reductionist and epiphenomenal viewpoints, the strength of whose arguments should not be underestimated, but it is clear we should proceed with caution.