Electrochemical Events in the Brain Information

Acknowledgements:

Many of the ideas that I present in this paper, such as the hypothesis of consciousness as an irreducible, fundamental aspect of reality analagous to the phenomenon of electric charge in physical systems; the need for a conscious entity to interpret the electrochemical events in the brain; and recent discoveries in the field of deterministic chaos which render the laws of physics flexible enough to allow interaction between the conscious self and his physical body, come originally from Dr. Richard Thompson, a mathematician at the Bhaktivedanta Institute in San Diego, California. I am deeply appreciative for his kind help and inspiration.

I also wish to thank neurophysiologists Margaret Livingstone and John Eccles for providing detailed information about the process of visual perception, Dr. Michael Sabom for providing detailed reports of autoscopic phenomena and a scholarly analysis of their significance, and Dr. Ian Stevenson for providing well documented cases that suggest that the conscious self can move from one physical body to another.

1. The intrinsic nature of consciousness

Since time immemorial philosophers have asked the question: "Who am I?" The obvious response to this question is, of course, "I am my physical body." This is natural since, if my body is injured, I feel pain. If the injury is severe enough, then my ability to perform certain activities is impaired. Also, certain stimuli in relation to my body result in an experience of pleasure for me. In other words, a change in the physiochemical situation of my body results in a change in the contents of my consciousness. Thus, our ordinary daily experiences seem to repeatedly reinforce our conviction that we are our bodies. No one would deny that there is a relationship between me and my body, but the real question is: Precisely what is this relationship?

Those who are more sophisticated will undoubtedly say that, in addition to being my body, I am also my mind and intelligence. But are not the terms "mind" and "intelligence" nothing more than mere names for elaborate systems of electrochemical reactions in the brain? If this is true, then the real thing taking place are the electrochemical reactions, and the words "mind" and "intelligence" are just superficial names for these more fundamental reactions.

Ultimately, then, those who answer the question "Who are you?" by saying "I am my physical body" or "I am my body, mind and intelligence" are really saying that "I am a complicated system of coordinated electrochemical reactions in my physical brain and body." Carried to its logical conclusion, this really means that ultimately I do not exist. The real thing occuring are the electrochemical interactions, and the word "I" is just a term for a certain temporary state of organization in the underlying chemical phenomena.

The philosophical schools known as "functionalism" and "behaviorism" maintain that all aspects of a human being can be adequately described in this way. Functionalism is based on the concept

that all human behavior can be duplicated by appropriate computer programs, and it provides the philosophical basis for research in the branch of computer science called "artificial intelligence". According to these philosophies, a complete description of human behavior can be given in the following way:

1. A certain environmental stimulus is specified as the input.

2. The senses of the physical body generate a systematic pattern of electrochemical pulses that encodes certain aspects of this input stimulus.

3. Transmission of this systematic pattern of pulses to the brain.

4. The performance of sophisticated information processing operations (analogous to those performed in computers) on this pattern of pulses by elaborate neural networks in the brain. The result of these operations is the production of a pattern of output electrochemical pulses.

5. This output pattern is transmitted along certain motor nerves to the appropriate muscles.

6. This results in a sequence of coordinated muscular contractions that carry out a desired activity. This constitutes a person's external observable behavior.

Let us suppose, for example, that I hit my thumb with a hammer. This results in damage to the tissues of the thumb. Nerves in the thumb are stimulated and a systematic pattern of electrical pulses is transmitted to the brain. Certain aspects of the physiological damage in the thumb are encoded in this pattern of electrical pulses.

According to neurophysiology, the brain contains billions of neurons which are interconnected in such a way that they form special circuits called neural networks that are able to perform sophisticated information processing tasks. These neural networks are analogous to the networks of silicon logic gates used in computers. It is believed that certain neural networks process the pattern of electrical pulses coming from the senses and extract certain features of this pattern. I will discuss this in greater detail in the second chapter.

When the pattern of electrical pulses from the senses reaches the brain, it causes a highly complicated pattern of changes to take place in the neurons there. Various electrochemical reactions take place such as the pumping of sodium and potassium ions through neural cell walls and the releasing of certain molecules that function as neurotransmitters. It is by means of reactions such as these that electrical pulses are transmitted from one neuron to another (this is described in greater detail in section 2.1.1.5). These kinds of reactions are also responsible for the logical functioning of neurons. By this it is meant that, given a number of input signals, a neuron will produce an appropriate output signal. In this regard the functioning of a neuron is analagous to the functioning of a silicon logic gate, such as an "and" gate or an "or" gate, used in modern computers.

In general, these kinds of reactions can be described in terms of the motion of charged particles and the formation and dissolution of various chemical bonds. The division of physics that describes the formation of chemical bonds is called quantum mechanics. The quantum mechanical picture of an atom shows certain regions, called electron orbitals, where electrons have a high probability of being found. The way in which the electron orbitals of an atom interact with those of other atoms determines the nature of the chemical bonding between these atoms.

Thus, according to the modern scientific picture, the electrochemical activities in the brain reduce down to a very long list of the activities and interactions of various subatomic particles such as electrons. Each of these particles possesses only a few simple characteristics such as charge, mass and spin. Thus the mode of interaction and characteristics of each of these subatomic particles could be described by a few simple equations or a short list of numbers.

Ultimately, the entire activity of the brain can be described as a long list of numbers corresponding to the states of the various subatomic particles that make up the brain. The numbers in this list would be changing constantly as the various electrochemical states of the brain change in response to changes in the physical body and its environment.

A pattern of output pulses is generated by the action of certain neural networks in the brain. This output pattern is transmitted along certain motor nerves to various muscles, such as the muscles of the hand and arm, resulting in a characteristic waving of the hand, and to certain facial muscles, resulting in a characteristic contortion of the face. Part of the output pattern is also transmitted to the muscles that control the vocal chords, resulting in yelling and cursing. In this way, behaviorists and functionalists describe the activity of hitting one's thumb with a hammer.

We note that although the details may vary, they would also describe other human behavior, such as eating, running, laughing, analyzing mathematical equations, falling in love, etc in the same basic way. In fact, behaviorists and functionalists are committed to the philosophy that all human behavior without exception can be completely described in similar terms -- in other words, in terms of the activities of neural networks in the brain and, more generally, electrochemical reactions in the body.

There are certain types of long-term purposeful behavior such as, for example, embarking on an eight-year study program to achieve a Ph.D. degree in physics, that involve elaborate planning and activity in which a person's actions are obviously more than just immediate reactions to environmental stimuli. Such behavior would be described by behaviorists as the result of past environmental stimuli working in conjunction with certain neural networks in the brain. For example, suppose that a father strongly desires that his son become a physicist. When the child is young the father naturally tries to interest his son in physics in many different ways over a period of many years. This is the environmental stimulus, and it is stored in the child's memory which, according to behaviorists, must also be a physiochemical process in the brain. They would also say that working in conjunction with this stimulus stored in the memory are elaborate neural networks that inspire one with a strong drive to become a success in his chosen field. This is the position of the functionalists and similar behavioristic philosophers.

What can we say about this position? Such a description involving the action of neural networks in the brain, if elaborated in sufficient detail, may be an adequate explanation for certain types of human behavior such as those involving immediate responses to certain environmental stimuli. But it is not at all clear that such a description is an adequate explanation for long-term purposeful behavior. It is certainly true that behaviorists have not yet rigorously identified which neural networks in the brain are actually responsible for specific types of long-term goal-directed behavior. Which neural networks inspire one with a strong drive to become a physicist? Which neural networks are responsible for the intense interest in and life-long dedication to music exhibited by great musicians and composers such as Mozart, Beethoven and Bach? And which networks are responsible for the inspirations of great artists such as Michelangelo?

Although these questions are a challenge to the behaviorists' position, there appears to be a much more serious challenge. There appears to be an aspect of human existence that can not be adequately described in terms of electrochemical phenomena in the physical brain and body. This is the aspect of human conscious experience.

When I hit my thumb with a hammer, I have a distinct conscious experience, which is the experience of a specific kind of pain. When I see a sunset I have a distinct conscious experience. Each human activity gives rise to a specific conscious experience. Careful thought about the meaning of conscious experience in general reveals the fact that conscious experience is something qualitatively different from the physical and electrochemical events described earlier.

It is definitely true that a specific pattern of electrochemical events in the brain gives rise to a specific conscious experience, and I shall discuss this in great detail in the second chapter. But the point I want to make here is that conscious experience is completely different from electrochemical events and physical phenomena in general.

Consciousness of the act of hitting my thumb is different from the act of hitting my thumb, and consciousness of electrochemical phenomena is different from electrochemical phenomena. In order to account for consciousness of something, there must be more than just that thing itself.

Human beings on this planet have a considerable number of features in common. We are all born of similar parents, our physical bodies are similar, and our goals and needs are also similar. It would therefore be exceedingly strange if only one out of all of these billions of human beings had internal conscious experience and all the others did not. Therefore it is reasonable to suppose that all human beings possess internal conscious experience. My internal individual conscious experience is certainly subjective, but the fact that all human beings possess consciousness means that consciousness is an objective feature of reality in general. Therefore, any philosophical system that fails to explain the nature of consciousness must be drasticly incomplete.

It is noteworthy that prominent scientists in a number of fields have recognized the distinction between consciousness of a material phenomenon and the material phenomenon itself, including Roger Penrose, Professor of Mathematics at Oxford University (1990); the Nobel Prize winning physicist Eugene Wigner (1964); the Nobel Prize winning neurophysiologist John Eccles and prominent philosopher Karl Popper (1977); and Jerry Fodor of the Artificial Intelligence Department of the Massachusetts Institute of Technology.

Although Professor Fodor is a proponent of functionalism, he nevertheless admitted (Fodor, 1981) that: "Many psychologists who are inclined to accept the functionalist framework are nevertheless worried about the failure of functionalism to reveal much about consciousness. Functionalists have made a few ingenious attempts to talk themselves and their colleagues out of this worry, but they have not, in my view, done so with much success."

There seems to be a serious problem here. I am conscious, but none of the structures or processes in my physical body and brain can account for my consciousness.

1.1 Panpsychism

Some philosophers postulate that consciousness is an inherent feature of matter itself; in other words, each arbitrarily small unit of matter possesses consciousness. This philosophy is called "panpsychism". But the problem with panpsychism is that, for example, if each electron in a man's brain (say the brain of a man named Mr. Jones) were conscious, then the only consciousness in his brain would be the billions of disunited individual states of consciousness of each of the electrons and not the consciousness of Mr. Jones. The nature of consciousness is such that individual consciousnesses do not combine to form an overall consciousness.

In order to illustrate this point, consider a version of philosopher John Searle's Chinese Room example. Consider a computer that consists of thousands of people sitting at desks in a very large room. Each person receives a piece of paper from one of his neighbors (for the sake of brevity, throughout this paper I use "his" in situations where "his or hers" should be used. I hope that no one feels offended). On this paper are certain marks. According to well defined rules, each person makes further marks on this piece of paper and passes it to one of his neighbors. If the rules are properly defined, this group of people can perform any information processing task now performed by electronic computers. A computer can be physically embodied in various forms, such as electric currents in silicon chips, the passing of written notes among a group of people, a system of gears and wheels, etc. The physical means whereby the calculations are performed is not important -- the important thing is that the calculations are performed properly.

Let us suppose that the rules are defined in such a way that the group of people acting as a computer (from now on called the group computer) is able to answer questions in the Chinese language (it is now possible to program electronic computers to provide reasonable answers to certain questions in human languages). Let us also consider the situation in which none of the people in the group understands Chinese or knows that the purpose of the group is to answer questions in Chinese. Each person is simply making marks on paper in a mechanical fashion without understanding the purpose of this activity.

A piece of paper containing a question written in Chinese enters through one door of the room of the group computer. The people make marks on pieces of paper according to the rules. The result of this is a series of Chinese characters that exit through the other door of the room. If the people sitting at the desks have followed the instructions properly, this group computer is able to provide realistic answers to questions in Chinese.

But none of the people understand Chinese. Within the room the only type of consciousness present is that of each person, who is only conscious of mechanically making marks on a piece of paper, and who is not even conscious of the purpose of the group. There is no overall consciousness of answering questions in Chinese. This is what we mean when we say that there is no overall or group consciousness in a group of conscious persons.

Sometimes people talk about a "group spirit or consciousness" but this is an innacurate use of the word consciousness. Of course, the people in a group may influence each other in various ways. But the people in a group influence the contents of each other's consciousness, they do not change the fundamental fact that each person has his own individual conscious experience, and these individual conscious experiences are the only kind of conscious experience present in the group.

Now let us compare this group of conscious persons to the group of hypothetical conscious electrons in Mr. Jones' brain. Granting that each electron is conscious, we still have the problem that each electron has its own individual conscious experience. Thus there would be a multitude of disunited individual conscious experiences of each of the conscious electrons, but there would not be the consciousness of Mr. Jones. Regardless of what each electron is conscious of, the only type of consciousness in Mr. Jones' brain would be a multitude of such individual electronic consciousnesses.

If Mr. Jones happened to be walking down the street, he

would naturally be conscious of the people on the sidewalk and the cars in the street. He is conscious of them because he possesses suitable senses, such as eyes and ears, that are able to pick up gross material stimuli (the existence of consciousness does not depend on senses, but in order to be conscious of certain material phenomena, there must be suitable sensory mechanisms to transmit material data to the conscious observer). According to modern physics, electrons do not possess suitable senses, hence even if they are conscious, the electrons within Mr. Jones' brain would be utterly unaware of the cars and people on the street. We have used the example of electrons, but the conclusion is the same if we consider any subatomic particle. Thus we see that the philosophy of panpsychism is unable to account for human conscious experience.

How, then, can we account for human conscious experience? Earlier we discussed how electrochemical activity in the brain fails to account for human conscious experience (not granting any special property such as consciousness to each unit of matter, but simply realizing that consciousness does not emerge from the interaction of purely material elements). Then we considered the philosophy (panpsychism) in which each arbitrarily small unit of matter possesses consciousness. But this also fails to account for our conscious experience.

1.2 The hypothesis that consciousness is a

fundamental, irreducible aspect of reality

Because consciousness does not emerge from the interaction of purely material elements, it is not unreasonable to consider the hypothesis that consciousness is a fundamental, irreducible aspect of reality. Mathematician Richard Thompson (1989) points out that in physics, the phenomenon of electric charge is considered to be fundamental and irreducible -- in other words, electric charge can not be explained as the interaction of other, more fundamental, entities. Electric charge must be postulated as an extra primitive element in physical systems. Thus, within modern physics it is not unprecedented to recognize a fundamental quantity such as electric charge.

Let us consider, then, the hypothesis that consciousness, like electric charge, is an irreducible, fundamental feature of reality. Each person has his own individual conscious experience. Let us postulate, then, that within the body of each human being there is a fundamental irreducible particle called "the conscious self" or just "the self" for short.

The reason that we have selected the words "the conscious self" to describe this quantum of consciousness is because this particle is, in essence, who we actually are. As outlined in the above discussion, we have been logically forced, step by step, to this conclusion in order to account for human conscious experience. Thus, according to this analysis, within the physical body of each human being there is one particle, called "the self", that identifies with that particular body and is able to use the senses of that body.

There may be many individual quanta of consciousness within each physical body, but only one of them is able to use the senses of that body, and only one of them identifies himself as that particular body.

The self possesses the power of consciousness and identity. I am actually the self, I am not my physical body or brain. The physical body and brain are sophisticated machines. In particular, the brain is a sophisticated information processing machine like modern electronic computers. But I am the conscious self, and I am qualitatively different from the physical and electrochemical interactions taking place within the brain and other organs of my physical body.

There is undoubtedly a relationship between the electrochemical phenomena in my physical body and the contents of my consciousness, but I (my actual self) am fundamentally completely different from such electrochemical phenomena.

This raises many questions about the interaction between me and my physical body. In particular, if I am completely different from my physical body, then why does damage to my physical brain impair my ability? And how do I, who am non-physical, interact with the structures of my physical body? What are the mechanics of this interaction? If I am not my physical body, then why do I identify myself as it? Why do I experience pain or pleasure when certain physical and electrochemical reactions take place in my physical body? How do such reactions give rise to my experience of pain or pleasure? These are all questions of great importance, and in the next few sections I shall outline a hypothesis that may help to shed some light on them.

2. How the interface works between the fundamental particle of consciousness called the self and his physical body

"Interactionism" is the technical philosophical term for a philosophy that postulates a non-physical particle called the self that interacts with his physical body. A central question in interactionistic philosophies is: Precisely what is the nature of the interface between the self and his physical body? Let us try to clarify the nature of this interface by examining the processes of sense perception and willed action.

2.1 Sense perception: The flow of information from the physical body to the conscious self

The conscious self who identifies with a particular physical body obtains information about that body and its environment through the action of his physical senses. It is important to recognize that we are not directly in contact with the physical world! In fact, our only contact with the physical world is through a very indirect means -- our physical senses. The reason that this is described as indirect is that our physical senses break down the stimuli coming from the physical world into a series of electrical pulses that encodes certain features of these stimuli. This encoded information must be decoded, or in other words, the original information from the physical world must be reconstructed in order for the conscious self to understand it.

It may not be necessary to postulate such a decoding operation in order to explain certain types of behavior, such as those which involve more or less immediate responses to environmental stimuli, since such responses might be explicable in terms of neural networks in accordance with the scheme that I outlined earlier (chapter 1, steps 1 through 6). In fact, it is conceivable that a machine could be built that duplicates such behavior (such a machine would perform steps 1 through 6 above). This is the goal of the field of endeavor known as "artificial intelligence." Due to the great complexity of the human brain and body, man-made machines are not yet able to adequately duplicate many aspects of human behavior, but it is hoped that technological advances may someday overcome this problem. There appears to be no fundamental reason why a machine could not duplicate the encoding function of the senses and the subsequent information processing activities of the neural networks in the brain, since the human brain and body are, according to modern science, nothing more than sophisticated machines. We simply have to figure out in greater detail precisely how the brain works and then build a computer that can work in the same way.

But if we want to explain how a person becomes conscious of environmental stimuli, then there must be a process whereby the complex electrochemical events in the brain are translated into the appropriate conscious experiences in the self. Let us now examine why such a translation process is needed and how it might work.

The series of electrical pulses produced by the physical senses that encodes an environmental stimulus is transmitted to the brain where it changes the overall pattern of electrochemical states in the billions of neurons in the brain. Each human activity establishes a specific electrochemical pattern in the brain. For example, the act of hitting one's thumb with a hammer establishes one specific pattern, whereas the act of seeing a sunrise establishes another. The act of eating pizza establishes yet another. Each one of the above examples, along with a huge variety of other bodily and mental stimuli routinely experienced by human beings, gives rise to a certain pattern. Each one of these patterns is distinct from all the others.

Let us consider the hypothetical situation in which you are looking inside someone's head and you are able to directly observe, at the molecular level, the electrochemical events that routinely take place in the brain. You would see activities such as the pumping of sodium and potassium ions across neural cell walls and the releasing of certain molecules that act as neurotransmitters. You would also see the formation and dissolution of various types of chemical bonds between the atoms. There are billions of such molecular events taking place every second within the brain.

It seems that, based on the latest research in neurophysiology, each particular electrochemical pattern in the brain is actually a code for a specific conscious experience, but you do not understand the language of electrochemical events in which the code is written, and thus you would be unable to realize what experience the person (whose brain you are observing) is having. To you, it is just a meaningless pattern of electrochemical activity -- you have no idea whether the person is experiencing pain or pleasure.

To illustrate what we mean by a "code", consider the English words that you are reading now. The series of ink marks on this page are a code. The series of marks "g r a n d m o t h e r" are ultimately nothing more than funny-looking marks on paper. A person who does not know that each letter is a code for a certain kind of sound and that each word has a specific meaning would surely see these letters and words as meaningless marks on paper. But those who understand English have learned this code. For them, the marks "g r a n d m o t h e r" have a clear meaning. (Try reading a language that uses characters the meaning of which you do not know -- for example, Chinese, Arabic, Sanskrit or Greek).

If that person himself were somehow able to directly see, at the molecular level, these electrochemical events in his own brain, he would also be unable to understand what they mean! The conscious experience that he is having while engaging in routine daily activities is correlated with the electrochemical events in his brain, but the correlation is established in such a way that he is not aware of how it is being established.

Within the brain electrochemical activities take place, and within the self various conscious experiences take place. Both of these things are real. Now the question is: How is the correlation established between these two real phenomena?

The overall electrochemical pattern in the brain changes constantly in response to changing environmental and internal stimuli. A change in the electrochemical pattern in one's brain results in a change in the contents of one's consciousness. But the electrochemical pattern is purely physical whereas the contents of consciousness are non-physical. Precisely how is a change in something physical closely correlated with a change in something completely non-physical? Let us call this correlation a "PNP link", where PNP means "Physical -- Non-physical". We shall explore the nature of this link in the next few sections.

2.1.1 The process of vision

As a concrete example of the process of sense perception, let us consider vision. Visual perception is taking place all the time within ourselves and others, and thus most people do not regard it as a particularly noteworthy achievement. But neurophysiologists who have analyzed in detail the workings of the eye and brain and scientists who have tried to duplicate human visual capabilities in machines have discovered the incredible sophistication of human vision.

2.1.1.1 Pattern recognition

For example, for the last few decades, computer scientists working in the field of artificial intelligence at top universities, such as the Massachusetts Institute of Technology (MIT), have worked very hard to try to program computers to recognize objects the way even ordinary human beings can. The seemingly simple act of recognizing apples and oranges is actually incredibly complicated, since apples, oranges and other natural objects may have a range of different shapes, sizes and colors, and appear different from different angles and under different lighting conditions. Nevertheless, even unintelligent human beings have no trouble recognizing such objects.

But to get machines to do so has thus far proven impossible. According to Dr. Richard Thompson (1989), computer scientists "have no idea how to represent the knowledge that a three-year-old child has of his mother's kitchen." In other words, even the most sophisticated modern pattern recognition programs are unable to endow a machine with the ability to recognize ordinary household objects as well as a three-year-old child.

Suppose the goal is to distinguish apples from all other objects. Apples can be a variety of sizes, colors, and shapes. Furthermore, they can be seen from a variety of different angles and under a variety of different lighting and background conditions. To distinguish apples from other objects clearly requires very sophisticated programming procedures.

What to speak of real objects that are, of course, exceedingly complex, even to get machines to discriminate between simple geometric shapes is a difficult task! To give an idea of how involved it is, according to Dr. Thompson (1981, p.120): "Many birds are highly discriminating in their response to the coloring and physical shapes of other birds. This means that they are able to make fine distinctions between complex patterns of color and form. Yet computer programs that can discriminate between simple geometric shapes have proven very difficult to write, and have involved many elaborate programming procedures. For example, one such program, called the 'MIT robot,' requires some 3.6 million bits of programming instructions."

It is thus clear that pattern recognition involves highly sophisticated analysis. Moreover, not only are human beings and many kinds of animals able to perform the sophisticated computations required to recognize real objects, they are able to perform these computations in an incredibly short period of time (often in less than a second). According to neurophysiologists, neural networks in the retina and various sections of the brain enable men and animals to accomplish visual pattern recognition.

The brain and retina are able to perform functions that are far superior to present-day computers. Yet, according to the modern conception, the brain and retina are nothing more than biological computers that use neurons as the logical elements. Hence, it should be possible, by devising clever enough experiments, to figure out how the brain and retina are performing sophisticated functions such as pattern recognition in the real world. During the last few decades, a tremendous amount of research work has in fact been devoted to this goal. Let us now look at some of the significant findings of this research.

2.1.1.2 The perception of color

The process of vision begins when light enters the eye and is focused on the retina. The retina consists of several layers of cells. The rearmost layer consists of special cells called "rods" and "cones" that are sensitive to light (photoreceptors). The total number of rods in the human retina is about 100 million, and the total number of cones is about 10 million. Rods are more sensitive to light than cones and are used under low light conditions in which the cones do not operate. But rods are not capable of color vision which explains why we see only black and white under low light conditions.

Cones contain special light-absorbing molecules called pigments. In the human eye, there are three types of cones: The first type contains pigments that are most sensitive to the short wavelengths of human vision (around 4000 Angstroms); the second type contains pigments most sensitive to medium wavelengths (around 5000 to 6000 Angstroms); and the third type contains pigments most sensitive to long wavelengths (around 7000 Angstroms).

Although each of these pigments is most sensitive to a given range of wavelengths, they nevertheless absorb light over a larger range of wavelengths. Thus the output signal from each of these three different types of cone cells is not very selective for wavelength, and hence each cone cell does not provide very much information about the wavelength of the light incident upon it. But if the outputs from the different types of cone cells are compared with each other, the resultant signal is more selective for wavelength.

According to neurophysiologist Margaret Livingstone (1988, p.68) a special type of neural network compares the strength of the output signals from the three different types of cone cells and generates a systematic pattern of electrical pulses that encodes the result of this comparison operation. Such a systematic pattern is translated by the PNP linkage (as mentioned earlier, "PNP linkage" means "physical -- non-physical linkage") in such a way that the self has the conscious experience of seeing a particular color. The conscious self can not understand by his own power what these patterns of pulses are supposed to mean. He is dependent on the PNP linkage to translate these patterns for him. Each pattern is a code for a particular color. Since people can be conscious of many different nuances of each of the major colors (such as yellow, red, blue, and green), there must be many different patterns each one of which codes for a particular nuance of color.

Later in this section I shall offer a detailed hypothesis concerning how the PNP linkage may operate. For the moment, however, it is important to note that although we commonly use the words "blue light" to describe light having wavelengths around 4000 Angstroms, there is nothing inherently "blue" about electromagnetic radiation that happens to have such a wavelength. Similarly, there is nothing inherently "green" about electromagnetic energy that happens to have a wavelength around 5000 Angstroms, nor is there anything inherently "red" about electromagnetic radiation that happens to have a wavelength around 7000 Angstroms. "Red", "green", and "blue" are non-physical states of consciousness in the self. They are qualitatively completely different from electromagnetic energy, regardless of its wavelength.

Electromagnetic energy is just a kind of energy. Why should electromagnetic energy having a wavelength of 4000 Angstroms happen to be correlated with the conscious experience of seeing blue? Energy having a wavelength of 4000 Angstroms causes the three different types of cone cells in the retina to generate specific output signals which in turn causes certain neural networks to generate a systematic pattern of electrical pulses that is displayed in a specific region of the brain. But this display is nothing more than a set of electrochemical events. Regardless of how sophisticated they are, it is true in general that neural networks do nothing more than perform information processing operations (such as comparing the strength of the output signals from the different types of cone cells) and display the results in the form of patterns of electrochemical events in neurons. Such patterns are qualitatively completely different from the conscious experience of seeing blue. Therefore, in order to create this conscious experience, something more than (and qualitatively different from) neural machinery is required. It is for this reason that I put forward the hypothesis of the PNP linkage. I do not lightly introduce such a radical hypothesis (the idea of a PNP linkage in the brain is radical in terms of the presently dominant mechanistic theories in the biological sciences). It seems, however, that something of this sort is required if we acknowledge the fact that conscious experiences are qualitatively different from electrochemical events in the brain.

As a concrete example of the process of color perception, let us suppose that a person is looking at a red car parked in front of a blue building. The red light reflected from this car is focused on one section of his retina. The three different types of cone cells in this section are thus exposed to this red light. The cone cells in this section that are most sensitive to red light produce signals that are stronger than the signals produced by the cones in this section that are most sensitive to shorter wavelengths. The color comparison neural networks in this section compare the strong signals from the red cone cells with the relatively weaker signals from the other types of cone cells and produce a specific pattern of electrical pulses that is a code for the conscious experience of seeing the color red. This code is translated by the PNP linkage in such a way that the self has the conscious experience of seeing red light in the appropriate section of the visual field. If the person who is looking at the red car is only (for example) two meters away from it, then the image of the car would occupy a significant percentage of the retina and hence the red light reflected from the car would be incident upon millions of different cone cells (recall from before that the total number of cone cells in the retina is approximately ten million).

However, the cone cells situated in the sections of the retina that receive the blue light reflected from the building are stimulated in a different way. In these sections, the red cone cells produce a relatively weak output signal whereas the blue cone cells produce a comparitively stronger output signal. The color comparison neural networks in these sections of the retina compare the outputs from the three kinds of cone cells and produce a pattern of pulses that is a code for the conscious experience of seeing the color blue.

Light entering the eyes that is not purely red, blue or green would result in various strengths of the output signals of the three types of cone cells. The color comparison neural network compares the relative strengths of the output signals from the different types of cones and produces the appropriate pattern of pulses which, when translated by the PNP linkage, results in the production of the conscious experience of seeing the appropriate color.

2.1.1.3 The processing of visual information in the brain

The neural networks responsible for the analysis of various aspects of the incoming light (such as its color and intensity) are situated in the retina and various regions of the brain. There is considerable evidence that the analysis takes place in steps along specific pathways. Dr. Livingstone (1988, p.68) reported that electrical signals generated by the photoreceptor cells (rods and cones) in the retina are not immediately transmitted along the optic nerve to the brain. Instead, these signals are passed to special networks of neurons in the retina which process them and then send them to another layer of neurons in the retina called "ganglion cells".

Ganglion cells are of two different types -- large and small. The large cells do not discriminate between one type of cone cell signal and another. They are not color selective and thus they are not part of the color-analysis system.

But the small ganglion cells discriminate between the three different types of cone cells by comparing the signals received from them. Thus the output signals from these small ganglion cells are more color-discriminating than the input signals they receive from the cone cells.

The output signals from both the large and small ganglion cells are transmitted along the optic nerves to the two "lateral geniculate bodies" of the brain. Each of the two optic nerves consists of approximately a million nerve fibers.

Within the lateral geniculate bodies there are small neurons (called "parvo" cells) and large neurons (called "magno" cells). The signals from the small retinal ganglion cells are transmitted to the parvo cells, and the signals from the large retinal ganglion cells are transmitted to the magno cells. The parvo neurons are part of the system which processes information about color contrast, and the magno neurons are part of the system which processes information about luminance contrast. The functional significance of the magno and parvo systems will become more clear as we trace the path of visual information processing from the retina through various regions of the brain.

The output from the parvo and magno cells are then transmitted to another region of the brain called "visual area 1" of the cerebral cortex (situated at the rearmost part of the brain). Neurophysiologists describe visual area 1 as consisting of six layers, one above the other.

If visual area 1 is stained in a certain way, a special pattern of light and dark regions can be observed in its upper layers. Dr. Livingstone and her colleagues decided to call the dark regions "blobs", and the lighter regions that surround them "interblobs." Clever tests revealed (Livingstone, 1988, p.71) that "the interblobs receive input from the parvo system, layer 4B (of visual area 1) receives input from the magno system and the blobs seem to receive input from both."

During the last few decades, numerous tests have been performed at a number of different universities in which a microelectrode was inserted into various regions of visual area 1 and other parts of the brain. By carefully positioning the microelectrode just outside of a neuron, one is able to detect the electrical pulses produced by this particular neuron (Popper and Eccles, 1977, p.265) without disturbing its functioning.

In a typical test, various objects are displayed before the eyes (in other words, "in the visual field") of a fully conscious person at the same time that the microelectrode is positioned near a particular neuron in his brain. The goal is to determine which types of visual stimuli cause this particular neuron to fire.

As mentioned earlier, Dr. Livingstone and her colleagues identified three different subdivisions in visual area 1 ("blobs", "interblob regions", and "layer 4B"). They measured the responses of cells in each of these three subdivisions to various kinds of stimuli in the visual field, including shape, position, distance, movement, color, brightness and size. They discovered that the neurons in the various subdivisions displayed a great difference in their responses (Livingstone, 1988, p.71): "The blobs contain cells that are highly selective for color or brightness but are not at all selective for shape or movement. Interblob cells are selective for orientation but not for color or movement. An interblob cell may respond to a vertical bar, for instance, regardless of how it moves or whether it is black, white or colored -- the only criterion is that the bar be vertical; that same cell will not respond to bars in any other orientation. Cells in layer 4B are also unselective for color, but they are selective for orientation and movement; a cell in this system, for example, will respond either to horizontal bars that move upward or to vertical bars that move horizontally but not to both".

Signals from these three subdivisions of visual area 1 are transmitted to a nearby region of the brain called visual area 2. The same staining technique revealed the fact that visual area 2 also contains at least three significant subdivisions, called "pale stripes", "thick stripes", and "thin stripes." Dr. Livingstone (1988, p.71) said that: "The color-selective blobs of visual area 1 provide input to the thin stripes of visual area 2, which continue the processing of color information. The orientation selective interblobs provide input to the pale stripes, which process the information in a way that suggests they are involved in shape analysis. The magno system provides input to the thick stripes, which analyze information about stereoscopic depth."

Information from the thick stripes of visual area 2 is then transmitted to another part of the brain called the middle temporal (MT). Many of the neurons in this part of the brain are sensitive to movement. It is also believed that the middle temporal is responsible for stereopsis. Stereopsis is a function of the brain which estimates how far away an object is based on the slightly different images of this object in the two eyes.

Signals from the thin stripes of visual area 2 are transmitted to a part of the brain concerned with color vision called visual area 4 (V4).

Various aspects of visual processing, such as the perception of shape, movement and color, seem to be performed step by step along independent pathways in the brain. For example, the "parvo-interblob-pale-stripe system" represents a sequence of information processing stages going from the retina to the parvo neurons of the lateral geniculate bodies and then to the "interblob" neurons of visual area 1 and then to the "pale-stripe" neurons of visual area 2. According to Dr. Livingstone, it seems that this sequential processing system enables one to see the shape of stationary objects in great detail. But it does not provide information about the color of these objects.

Another step by step processing sequence is the "blob-thin-stripe-V4" system which goes from the retina to the lateral geniculate bodies and then to the "blob" neurons of visual area 1 and then to the "thin stripe" neurons of visual area 2 and then to the neurons of visual area 4. Dr. Livingstone said (1988, p.72): "The blob-thin-stripe-V4 system processes information about color and shades of gray but not about movement, shape discrimination or depth. This system has a severalfold lower acuity than the interblob system and therefore sees objects in color but not in great detail."

The "magno-4B-thick-stripe-MT" system provides information about movement and how far away an object is based on stereoscopic analysis. But it provides no information about the color of an object.

The idea that different aspects of visual processing are performed by different parts of the brain seems to be confirmed by the various kinds of partial blindness exhibited by persons who are suffering from damage to specific parts of their brain. For example, in one case, a person is unable to recognize faces although he is still able to perceive shapes. In another case, a person is unable to see color, but he is still able to see shapes.

Nobel prize winning neurophysiologist John Eccles (Popper and Eccles, 1977, p.263) reported that there is no exact replica of the visual field displayed on a "screen" in the brain, although there is a region of neurons in the visual cortex (the rearmost part of the human brain) that contains a distorted representation of the visual field.

2.1.1.4 Certain neurons respond only to specific

shapes in the visual field

Dr. Eccles (1977, p.266) also reported that some neurons respond only to specific stimuli in the visual field: "there are neurons that are specially sensitive to the length and thickness of bright or dark lines as well as to their orientation and even to two lines meeting at an angle." He also said that in the part of the brain called the "inferotemporal cortex" of monkeys there are special neurons that respond only to specific shapes in the visual field (1977, p.268): "neurons may be fired by rectangles in the visual field and not by discs, or by stars and not by circles. Evidently some of the neurons have a remarkable feature recognition propensity. It is suggested that the feature responsivity of some neurons may be so specific that it is not discoverable in the limited testing time available in an experiment."

He mentioned that the inferotemporal cortex of monkeys corresponds to the "lower part of the right temporal lobe" in human beings, since it is in this part of the human brain that neurons respond to specific shapes, both simple geometric shapes and more irregular ones.

Dr. Eccles believes that the neurons which respond to specific shapes in the visual field are able to do so because they receive input pulses from the appropriate neurons that respond to simpler forms, such as lines at particular orientations, that can be fitted together to compose the specific shape. For example, a neuron that responds to a triangle in the visual field does so because it receives input pulses from neurons that respond to lines at the appropriate angles for composing the triangle.

If this idea is correct, then it suggests the following scenario for the recognition of simple geometric forms: A geometric form (a triangle, for example) is displayed before the eyes of a conscious individual. The appropriate photoreceptor cells of the retina are stimulated and consequently generate electrical pulses as output. This output is sent to certain regions of the brain including the "parvo" cells. The output from the parvo cells is sent to the "interblob" cells. As mentioned earlier, Dr. Livingstone reported that an interblob cell that responds to a line at a particular orientation does not respond to lines at any other orientations. The output from the photoreceptor cells thus results in the firing of three particular neurons, each of which is exclusively responsive to one of the lines that make up the triangle present in the visual field. The output pulses from each of these three neurons are transmitted to one neuron that responds to this triangle.

2.1.1.5 How signals are generated within neurons and transmitted to other neurons

In order for this system to function properly, output signals from certain neurons must be transmitted to certain other neurons. In the brain this is accomplished by interconnections between the neurons called "axons" and "dendrites."

The main body of a neuron is called the soma. It contains the nucleus and other organelles that are essential for cellular functioning. Output from the neuron is transmitted along the axon, which typically branches into a number of nerve fibers. A signal can be sent along each of the fibers, thus allowing the output of one neuron to be transmitted to many other neurons. At the end of each such fiber is a special organelle called the synaptic knob.

The output of a neuron is in the form of an electric pulse that travels along a nerve fiber. The