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 投稿者:.  投稿日:2015年 3月 4日(水)14時51分54秒



How does the mind arise from the brain?

 投稿者:永井哲志  投稿日:2013年 1月29日(火)10時56分59秒
  How does the mind arise from the brain?
The study of comparing the neur al stem cells with the mer istematic cells in a cherry tree
Research notes from the Minamiohya Clinic, 2012     Authur : Tetsushi Nagai

1. Foreword
2. On what grounds can we compare neural stem cells and meristematic cells ?
3 What is the mind??Neuroscientific approaches up to the present
3.1 Where is the mind?
3.2 Understanding the mind with psychology
3.3 Understanding the mind with neuroscience
3.4 The problems with neuroscience
4. Development of the brain and a cherry tree
4.1 A new theory based on the existence of neural stem cells
4.2 Neural stem cells and meristematic cells
5. How does the mind arise from the brain?
5.1 Conjectures based on brain development
5.2 The relationship between form and function
5.3 The role of time
5.4 Self-consciousness
5.5 Intuition
6. The development of the mind
7. Afterword

ABSTRACT(long version)
A machine operates based on the systems with which it is provided; the behaviour of humanbeings, however, is based not only on instinct but also on thoughts that originate in the mind.What is this mind, and how does it arise from the brain as a function? These questions remainunanswered. In an attempt to clarify these issues, psychology deals with the mind by splittingit into various parts, while,inneuroscience, it is believed that if it can be determined exactlywhere in the brain these parts are localized (i.e., the theory of functional localization)?and ifwe then investigate how the millions of cells there work together?we will finally be able tounderstand the relationship between the mind and brain. However, even if a deficit occurs atsome location in the brain?even one that induces some functional impairment?as long as
the brain recognizes its own existence (i.e. is self-aware), then that intuition, which forms thevery foundation of the mind, will also continue to exist. Basically, according to the variousanalyses based on the theory of the localization of brain function, the mind is not locatedanywhere in the brain. This theory of localization of function cannot in fact explain the minditself. The mind that is born of the brain must be thought of as one of the various phenomenaof life, which, just like the organs in the human body, all begin from various types of stemcell division.
Plants, animals, and indeed all living things have mechanisms in common. That is to say,from birth until death, at all times, on the basis of inherited genetic information, everyorganism is able to discriminate between self and non-self; every organism also possessesundifferentiated growth points (parts which grow with the passing of time) that grow withoutcessation. When these growth points complete their differentiation,they are left behind as akind of trace while new growth points are born. With the repetition of this process, newmemories are accumulated, and an individual’s existence thus constantly changes. Thesegrowth points, along with the mechanism of memory, can be said to be the building blocks oflife.
In plants, these structures, which respond to the surrounding environment and grow based onthe differentiation of meristematic cells, are visible to the naked eye. On observing the broadleaveddeciduous rosa multiflora sakura (hereafter referred to as ‘the cherry tree’), we canconclude that the derivation of large branches and twigs from the single thick trunk is similarto the anatomical development of the structures of the human brain. The present studyexamines the growth of a cherry tree and usesthese observations to determine what role theactivity of the huge numbers of neural stem cells has in the creation of the phenomenonknown as the mind.
Neural stem cells (which here correspond to the cherry tree’s meristematic cells) are located in the various regions of the brain (the cherry tree’s twigs), respond to information from theexternal environment, and differentiate into nerve cells and glial cells (buds, flowers, and leaves in the cherry tree). As part of this process, new structures are built as memories and systems (new leaf stems in the cherry tree). Meanwhile, old or damaged nerve tissue that cannot be reused is discarded (in the cherry tree, this corresponds to the withering and breaking off of branches that do not receive sufficient sunlight), and the memories contained within are lost. In this way, we see that as long as they live, both the brain and the cherry tree are constantly developing.
Thus it can be conjectured that the mind, on the basis of information gained from both theoutside world by groups of neural stem cells (groups of meristematic cells in the cherry tree)and its own memories (the trunk and branches of the cherry tree), is essentially the activity ofdifferentiation with a view to the future.

ABSTRACT(short version)
Human behaviour is controlled not only by instincts but also by the mind. However, therelation of the mind to the brain has not been fully explained. In conventional interpretations,the mind is not believed to be located at any one spot in the brain, which, if true, suggests thatwe will remain forever unable to explain the mind completely, regardless of ourunderstanding of the brain’s local functions. Brain development resembles the branchingprocess of the cherry tree, in which the trunk branches off into limbs and limbs into twigs. Asa novel method of understanding the mind, we compare the patterns of neural stem cellactivity with the growth patterns of the cherry tree. Studying plants in the natural worldenables us to keep an open mind.
Each neural stem cell (the meristematic cell in the cherry tree,) in the cerebrum (the
branches) changes into neurons or glial cells (buds, flowers, and leaves) in response toinformation from the external environment. New tissue is added to the memory (new stems).Meanwhile, old neurons die (just as twigs that have long been in the shade will break off).Growth continues as long as life continues.
This novel perspective suggests that the mind encompasses the entire cerebrum, whose neuralstem cells (the meritematic cells in the cherry tree) retrieve information from both theexternal environment and internal memory (the tree’s stem and limbs).

心 mind
脳 brain 大脳 cerebrum
神経幹細胞 neural stem cells
生長点細胞 meristematic cells
記憶 memory
自己意識 self-consciousness
直観 intuition
ニューラル ネットワーク  neural network


Despite recent technological advances, many things about the brain remain unclear to us,such as the structures that give rise to brain function, the activity of the brain, and braindiseases and their treatment. Our current knowledge is merely the tip of the iceberg. Researchhas shown only that every part of the brain contains a great number of nerve cells (neurons),as well as supportive glial cells, with blood vessels that crisscross its surface.
Under the surface of the brain, there are hidden things that we have not even begun to
understand (Masao Itō, 1998). For example, we are completely unable to explain how
memories, thoughts, and emotions are created simply by neurons and glial cells, even if wevainly attempt to explain these processes based on the phenomena of physics, the chemicalreactions that we have discovered, or even the latest computer technology. This is becausethe brain comprises an uncountable number of cells, each of which has its own individual life and is able to alter itself and divide. Biology researchers have gone all the way down to the molecular level to solve this fundamental problem and have made valuable discoveries, but the relationship between the brain and mind remains unclear.
The workings of human life and the growth of a plant?for example, the symbolic broadleaved deciduous rosa multiflora sakura (hereafter referred to as ‘the cherry tree’)?are comparable in that they have a common life process. That is, as living things, both have cells that continuously differentiate into new cells. Similar to the human brain, the cherry tree has mechanisms that allow it to recognize itself and respond to its environment. Those structures are located at the ends of the tree’s roots and leaf stalks and are called meristematic cells.
These cells actively divide and are the points at which new tissues are created. Of course, this is not to say that a cherry tree?which is, of course, a plant?has an organ like a brain that can react simultaneously to external stimuli and give rise to thoughts and reactions. However, through cytodifferentiation of its innumerable meristematic cells, the cherry tree adjusts itself to the changing seasons and develops buds that grow into flowers, leaves, and branches. For a single tree, this is a marvellous achievement in terms of growth.
In recent years, cells known as neural stem cells have been discovered in the brains of human adults. These cells can be thought of as acting in a similar way to a plant’s meristematic cells. They possess what is called ‘diversity characteristics’, meaning that they have the potential to become many different types of nerve cell but have not yet undergone cell differentiation at the most detailed level. This discovery, overturned the widespread belief that ‘regeneration of neurons does not occur in higher animals’ (Gerd Kempemann, Fred H. Gage 1997). The discovery of these new neural stem cells suggests that the brain and plants possess and operate on the same kinds of growth mechanisms.
By using simpler modes of thought that differ from previous purely neuroscientific methods, we may now be able to significantly advance our understanding of the mysterious and complex workings of the brain. Comprehending the mind is said to be the greatest challenge left to mankind; it is also one of the most difficult in principle. We cannot expect any significant progress if we persist in clinging stubbornly to traditional scientific methods.
In this article, the meristematic cells of plants and the neural stem cells of the brain are compared as a foundation for a novel theory of the workings of the brain. Rather than using standard scientific methodology, I will attempt to apply an intuitive approach to the question: ‘How does the mind arise from the brain?’

The French philosopher and mathematician Blaise Pascal (1623 ? 1662) said: ‘Man is a thinking reed.’ What kind of living thing did he mean by a ‘reed’? It is thought that plants neither think nor have feelings; indeed, for a plant, neither of these functions is necessary. Plants are easy to understand as living things. However, they have keenly developed senses: they cleverly adjust to changes in the natural environment and even have the ability to propagate by means of cloning.
In the distant past, biologists maintained that only plants and animals that could be seen by the naked eye should be classed as living things. However, with the invention of the microscope and other such equipment, microbes and other organisms that could not be seen with the naked eye came to be classified with animals and plants under the general term of living things. Living things differ from inanimate objects because the former have cells. The cell is the smallest unit possessed by all living things and acts as a microscopic ‘room’ for the organism’s genes (DNA).
When it comes to the phenomenon of life, all living things on Earth?not just animals, butplants, amoebae, and bacteria, too?share the same basic mechanisms. In addition, they are largely the same in their basic cell structure, basic metabolic functions, genes, and even, to date, the code of their chemical molecules. Thus, when comparing them as living things at the cell level, animals and plants are basically the same. One large difference between them,however, is that plants do not have to acquire energy from other animals, because plants obtain their energy from the sun. Furthermore, animals have various internal organs. Of particular interest is the brain, which allows animals to distinguish themselves from others,control the other organs of the body, and operate as one complete organism.
The most unusual role of the human brain is that it enables us to recognize our surroundings (i.e., self awareness). Understanding the structures of the brain is part of my work, but I believe it is vital basic knowledge for all of us. Due to the unfortunate fact that my clinic does not have the relevant specialized research facilities, I have been restricted in terms of methodology to observing the daily lives and activities of human beings, along with the cherry tree that I can see from my window.
Ever since ancient times, Japanese have considered the cherry tree a symbol of their
psychology as a people. Alongside us, the cherry tree changes with the seasons; first it
sprouts buds, then it flowers, then bursts into full bloom, and finally sheds its leaves and remains bare throughout the winter. The thought occurred to me that the grace, beauty, and strength of the cherry tree exhibit the very meaning of what it is to be alive?after which I was possessed to ask: ‘What is the mind?’

3.1 Where is the mind?
When we awaken from sleep, all our sensory organs?our eyes, ears, and skin?naturally become aware of the world around us. In addition to this awareness, we think and recognize based on our memories of our existence in society (otherwise known as self-awareness). Until now, what we called the mind had been defined simply as the origin of all mental activity in the brain or, alternatively, as the general term for mental activity. These vague definitions were due to the fact that the brain has no muscles; thus, we cannot directly view mental activity with the naked eye. These invisible brain activities are inferred on the basis of various external stimuli, e.g., facial expressions, behaviour, body language, and spoken language. Moreover, we also sometimes define the mind as a complicated ‘awareness’ that we can neither see nor describe in words. Sometimes, the mind is defined as the thoughts and ideas that arise seemingly of their own accord.
What is the mind? Where is it located? Human beings have asked themselves these questions since the dawn of civilization. Six thousand years ago, in Egypt, it was believed that the heart was the seat of the mind; four thousand years ago, in Babylonia, the mind was said to be in the liver. In Ancient Greece, with the advent of more systematic scholarship, it was said that the mind originated in the functions of the brain or heart. For example, Hippocrates (c. 460 BCE ? c. 377 BCE), the father of medicine, believed that the mind was ‘the functions of the brain’, the philosopher Plato (c. 428 BCE ? c. 347 BCE) believed that ‘the mind lies in the spinal cord’, and Plato’s pupil Aristotle (c. 348 BCE ? c. 322 BCE) thought that the mind was to be found in the heart.
Because Aristotle’s ideas had a great influence on European thinking, it was long believed that the heart was the seat of the mind. However, with the birth of modern science in the 17th century, the brain once more became the focus of attention. The French philosopher René Descartes (1596 ? 1650) claimed that the origin of thoughts, and the mind, was in a very deep part of the brain called the pineal gland, which was connected to the nerves of the eyes, thus making it able to sense light and secrete hormones. Similarly, the second-century Roman physician Galen (c. 130 ? c. 200), who devoted himself to anatomical research, believed that what he called ‘the flow of the spirits’ was not to be found in the brain itself, but inside cerebrospinal fluid-filled channels within the interior of the brain, which he called ‘brain rooms’.
There were many other such theories, but after the 17th century it was generally agreed that there was some relationship between the mind and brain. However, the nature of that relationship was an issue that split thought broadly into two schools. The first?the monistic theory?claimed that the mind and the mental activities of the brain were the same thing and that they were just two words for the same process; the second?the dualistic theory?claimed that the mind and brain were different things, different processes, and that the mind was independent from the brain.
The two theories fundamentally differed, which led to a long intellectual standoff. However, the dualistic theory was predominant because it was compatible with the principles of Christianity. As an example, in the 18th century, the French physician Julian Offroy de la Mettrie (1709 ? 1751) propounded a monistic mode of thought and demonstrated that according to the principles of physiology, nothing other than the functions of the brain could be responsible for human mental activity. Upon publication of his findings he was faced with a storm of vitriol from the Church and was forced into exile.
Today,however, we do not have the luxury of doubting the monistic theory. We accept that what we call our mind is a function of brain activity. It is undeniable that the human brain is created from a mesh of innumerable nerve cells and that all mental activities are spun from inside this mesh. However, regardless of where we search in the brain, there is no physical proof of this fact. Furthermore, there is still no answer to the question: How does the mind arise from the brain?

3.2 Understanding the mind with psychology
After plants put down roots into the earth, they cannot move. Instead, they must use their keen senses to adjust and adapt themselves to the seasons and environment in which they grow. We humans, however, do not simply repeat the same actions over and over in this way; we are aware of our environment, and our actions are controlled based on memories, emotions, moods, and thoughts that come from the brain.
Scientific research on human mental/psychological development began in 1879, when the German physiologist and philosopher Wilhelm Wundt (1832 ? 1920) founded the world’s first laboratory of psychological research at the University of Leipzig. However, the inner workings of the human mind are obscure and cannot easily be measured directly or objectively; thus the science of psychology attempts to clarify these internal psychological and emotional processes by means of objective research based on quantifiable external behaviours. In psychology, which deals with the relationship between hidden mental processes and external behaviours and uses both experiments and observation as research methods, the word ‘reactions’ is used rather than the word ‘mind’. Furthermore, psychology divides the processes of human life from birth until death into three stages?the activities of the mind, the actions born of these activities, and the human meaning that those actions have?and regards the mind as composed of many components. Due to recent developments in neuroscientific research methods, we have managed to understand the relationship of some of these components to the brain itself. However, we still cannot explain the essence of the innermost component that controls the other components on a fundamental level. This
innermost component has been variously referred to as the self, ego, soul, spirit, or one’s self and is thought to be the quintessence of life.

3.3 Understanding the mind with neuroscience
In ancient times, it was believed that pneuma was at the origin of all nature, human life, and all their associated workings. This word in Greek has various meanings, including breath, wind, and soul. Pneuma was invisible to the naked eye, but its movements could be heard and felt. It connected human being to human being, and human being to nature, and its existence was credited with enabling humans to live together and achieve greatness as individuals.
In 1791, Luigi Galvani (1737 ? 1798), an Italian anatomist and physician, discovered
electricity using the leg of a frog and thus paved the way for the discovery of the
neurotransmission system. The English chemist and theologian Joseph Priestley (1733 ? 1804) developed an innovative method of experimentation. Beginning with his discovery of oxygen in air, he also separated various different gases and eventually found that the heat within the human body was caused by chemical reactions. In 1774, Priestley visited France and explained his discovery of the constituents of air to the chemist Antoine Laurent Lavoisier (1743 ? 1794). Lavoisier immediately realized the significance of the fact that eventhings that are invisible to the naked eye are made up of many different substances. This led in turn to the chemical revolution that would form the foundation of modern chemistry and that thoroughly negated the idea of the existence of the metaphysical substance pneuma,which had been thought to be responsible for thermogenesis in the human body.
At this time, in an effort to keep up with developments in modern physiology, brain research also entered a period of extremely significant developments. Research by the English physiologist Charles Scott Sherrington (1861 ? 1952) revealed that transmissions between neurons were caused by electric signals and that transmission of these electric signals was due to a chemical agent found in the gaps between neurons (the synapses). Thus information is transferred within the brain via two types of transmission: chemical and electrical. The discovery of this ‘information transmission circuit’, which is known as a neural circuit or neural network, provided a stepping stone for continuing efforts to understand brain structure.
After the Second World War, W. Penfield (1891 ? 1976), a Canadian neurologist and
neurosurgeon who had studied under Sherrington, put into practice the contemporaneously formulated theory of the localization of brain function, which was based on the idea of electrical stimulation of the cerebral cortex during brain surgery. After obtaining the patient’s advance consent, he attached electrodes to various regions of the cerebral cortex, applied electrical stimulation, and observed the patient’s responses. The results he observed when he applied the stimulus to the region of the brain just above the ear had a decisive impact on neuroscience as a whole: Penfield’s experiment effectively proved the localization theory. However, despite the fact that he had proved that brain function was localized, Penfield
concluded that, ‘The mind is not inside the brain?it is located elsewhere.’
In 1958, D.H. Hubel (1926 ?) and T.N. Wiesel (1924 ?) discovered the optic nerve cells, which respond only to specific stimuli and specific conditions. This discovery set the precedent for the various hypotheses related to recognition cells, which were put forward during the 1980s and 1990s.
When we see the image of an object, our various nerve cells respond to that image. There are currently two basic schools of thought on how we recognize an image. The first suggests that there is a specific cell in the brain designed to respond to each individual image of an object. This idea takes the localization of brain function all the way down to the individual cell level. If we were to accept this hypothesis, it would mean that we each have, for example, a specific ‘granny cell’ that responds only to our grandmother’s face and, similarly, a specific ‘grandpa cell’ that responds only to the face of our grandfather. The second theory is that we have cells that all selectively respond to various characteristics of shapes, i.e., an object is displayed to us via a combination of these cells. According to this idea, each image of an object is displayed to us as a combination of the object’s particular characteristics; the information we receive is not necessarily localized down to the level of individual cells, and the information is displayed by a group of incomplete cells that have a number of possible responses.
From the 1970s to the 1980s, the discipline of computer science made immense advances. In parallel with this technological progress, the idea that the mental activities of the brain were similar to the data-processing functions of a computer gradually gained strength. With advent of the computational theory of neuroscientist David Marr (1916 ? 1998), the monistic theory of the brain became persuasive. Using as an example the fact that the information transmission circuit found in the synapses of the brain works in exactly the same way as acomputer, Marr proved in theory that it was possible to explain both the brain and a computer by invoking the same system.
The existence of such an information processing system showed that the brain is constantly processing information at extremely high speeds. However, at the same time it was recognized that the brain is an information processing system so complicated and so fast that no matter how many supercomputers one might link together, a machine did not stand a chance of keeping up. Despite this, computer science has expanded the methods that can be applied to investigating the many questions related to the mind that are raised by those invisible brain activities. Along with increased knowledge in the fields of anatomy, electrophysiology, experimental physiology, and developmental physiology, new brain activity scanning systems such as magnetic resonance imaging (MRI) and positron emission tomography (PET) were introduced during this period. These allow us visualize, via an onscreen image, the region of the brain that is responsible for recognition functions. Simulation technology, which is able to reconstruct neural networks/neural circuits and nerve systems, is also being utilized. With the use of these technologies, neuroscience research is advancing at a rapid pace. We are getting ever closer to the crux of the monistic theory, which states that the mind is to be found somewhere within the brain.

3.4 Problems with neuroscience

It is thought that the brain’s processing of information in the sensory mechanisms is carried out by the approximately 14 billion nerve cells that make up the cerebral cortex. Nerve cells are bound to each other at synapses. The total number of synapses in the entire cerebral cortex is as high as 105 x 14 billion. These synapses combine together, creating innumerable nerve circuit meshes. The nerve cells in these meshes do not remain fixed in place like part of a machine; rather they are constantly undergoing cell division and reproducing. Thus the nerve circuit itself is also constantly changing. Although these numberless billions of nerve cells all have the same genes, the cells have been created in different environments and at different times via cell differentiation. So, even if we regard all nerve cells and all synapses
to be identical, and add them together, this still does not explain the workings of the brain as a whole. The reality is that even if we focus our efforts and manage to ultimately explain themechanisms of one part of the brain in detail, we are still unable to explain the mind, which isthe sum of the functions of the entire brain.

Natural science aims to explore universal truths and laws, and neuroscience then applies thatsystematic knowledge. However, both natural science and neuroscience ultimately regard thebrain as if it were something inorganic. The knowledge obtained in this manner is taken asobjectively proven fact, which is then applied to every given phenomenon, no matter howlimited the sphere or in what type of organism it was found to hold true initially. Theprevailing belief that comprehending every phenomenon on a basic level requires that we beable to understand and interpret it has been the dominant mode of thought since the scientificrevolution. Therefore, based on this idea, scientists believe that if only we can discover newfacts about the brain, these facts can be interpreted via the brain-as-inorganic-matter mode of
thinking that has held sway until now. Basically, this mode of thought leads to the incorrectnotion that the ‘phenomenon of life’ and the ‘functions of the machine’, which both haveliving cells as their basic components, act based on the same structures. In the end, for us ashuman beings, the act of clarifying and understanding some given phenomenon is nothingmore than an attempt to satisfy ourselves, to feel secure, or, alternatively, to replicate saidphenomenon so as to make use of it in our daily lives.

With the abilities we have as human beings we must realize that just because we can
understand, accept, be satisfied with, and make use of the simple and universal structures asthey are, we cannot expect to understand and be able to replicate the basic structures of thephenomenon of life in the same way as we would a machine.


4.1. A new theory based on the existence of neural stem cells

There are several hundred billion nerve cells in the brain. These are made up of the meshes ofelectrically activated neurons and non-excitable glial cells, which help neurons functionproperly and whose number is ten times greater. Unlike other normal cells, a neuron issurrounded by multiple dendrites; one of those dendrites is longer than the others and iscalled an axon. Neurons communicate through a structure called a synapse, which connectsthe neurons together. Electrical signals arising from a neuron go through the dendrites and theaxons and are sent to neighbouring neurons by chemicals in the synapse. It is thought that thisnetwork, which sends signals to the neurons through the synapses, is the brain’s basic cellular
tissue structure (which I shall refer to as the ‘neural network’).

It used to be thought that most of the neural network, which produces the essential neuralfunctions, was formed during foetal development and that the cells would not divide againafter they were formed. It was also believed that the adult’ brain was larger than that of anewborn baby due to age-related increases in the number of glial cells, (which are separatefrom neurons); and myelin, (which acts as an insulator for synapses and for electricallyexcitable neurons and is produced during infant development). Furthermore, it was thoughtthat although tens of thousands of neurons perish every day in the adult brain, they could notbe replaced. This ‘textbook’ theory went utterly unchallenged until relatively recently.

In 1997, Peter S. Erikson (1936 ?), of Sahlgrenska University in Sweden, and Fred H. Gage(1940 ?), of the Salk Institute for Biological Studies, discovered that neurons are newlycreated every day, even in the brain of a fully grown adult?at least in the hippocampus,which is located in the medial temporal lobe of the brain and plays an important role inmemory and learning. Furthermore, in just the last few years, the discovery of neural stemcells?which do not differentiate into the cells of the nervous system and therefore have thepotential to become various types of cell?has overturned the conventional wisdom thatneurons are not newly created in the brains of adult higher-order animals.

As it has become clear that neurons are replaced in the adult brain, it can be further assumedthat the structure of the neural network is not fixed, but rather is constantly changing.Moreover, this discovery has given rise to the hypothesis that the mind is formed by theaccumulation of new information that is stored as memories.

4.2 Neural stem cells and Meristematic cells

Once a cherry tree has matured, it appears to have stopped growing. This is because as thetree is buffeted by winds and damaged by insects over the years, only the strong branches survive, and the number of meristematic cells?the cells able to produce new buds?continues to decrease. However, even an old tree with a severely depleted number of meristematic cells continues every spring to produce a small number of buds (which then bloom into flowers), puts out fresh green leaves, and thus continues to grow for as long as it lives. We can interpret this in terms of the brain by saying that although the number of neural stem cells decreases with age, the brain, just like the cherry tree, continues to put out new‘buds’, so to speak, and continues to develop as long as it lives.

Over the years, substantial effort has been devoted to understanding the extremely complexfunctions of the brain. Perhaps this is because we human beings see ourselves as specialorganisms, and therefore believe that we must have special qualities or mechanisms. However, if we treat human beings as just one type of organism, we can see that all living creatures?including plants, animals, fungi, and viruses?have mechanisms in common. In other words, from birth until death, at all times, every organism recognizes its self and its non-self and possesses undifferentiated growth points. Those growth points, which have finished differentiating, leave traces of themselves behind as memories, and as this process is repeated, the memories one possesses, as one’s ‘self’, change over time. It is thought that these growth points (which are able to differentiate) and memories (which have been created from these differentiated growth points) are the building blocks of life.

Through asymmetric division, neural stem cells, which are the brain’s growth points, growinto two different daughter cells: a new neural stem cell and a nerve cell. Because of the very large number of differentiating neural stem cells, the brain can play an important role as an organ (the neuron network structure)?namely, the continuous creation of an individual’spersonality by means of the constant differentiation of neural stem cells into nerve cells, in combination with information gleaned from the outside environment and accumulated memories. Once these nerve cells have finished their duties, the glial cells are left as memories. In the meantime, the next group of neural stem cells begins to differentiate; thus the neuron network is constantly updated and the brain keeps developing, just like a cherry tree.

Again, this concept is easier to understand if we liken the brain to a cherry tree. A cherry tree growing outdoors is constantly subject to natural stimuli; it is buffeted by wind and, exposed to the sun and rain. The countless number of meristematic cells in the buds on the tree’s branches sense light and temperature, differentiate, and put out buds, flowers, and leaves. In this way, the new branches that have grown over the years remain as ‘memories’, while new meristematic cells are produced. These growth cells gather together and eventually form a whole cherry tree?from the thick trunk to the numerous small branches growing out from it?that keeps growing. In short, both the brain and cherry tree continuously change and
develop, without limit.


5.1 Conjectures based on brain development

When considering how the mind arises from the brain, it is important to understand on a basic level how the brain occurs and how it is structured. The human brain comes into existence when one fertilized egg differentiates, producing a vast number of cells. This egg has the potential to differentiate into all of our given organs. At around the middle of the third week of the prenatal period, neural stem cells appear. In the early stages of the embryonic period, after repeated cell division and propagation, stem cells of the central nerve system called neural epithelial cells form a single blind-ended tube. On the upper end of the tube grow three ampulae, which will eventually develop into the brain. These three ampulae, from top to bottom, are called the prosencephalon, or forebrain; the mesencephalon, or midbrain; and
rhombencephalon, or hindbrain. The forebrain develops further, growing into the
telencephalon, or cerebrum, which swells out on both sides. It resembles the shape of a hemisphere and thus is called the cerebral hemisphere. The midbrain does not develop much further, but the hindbrain further differentiates into three sections: the pons, the cerebellum, and the medulla oblongata. The pons and the cerebellum together are referred to as the hindbrain, while the medulla oblongata is known as the myelencephalon.

The basic structure of the brain in vertebrates has unchanged little throughout evolution, and the greatest evidence of evolution can be seen in the development of the cerebrum. For instance, in reptiles the cerebrum is merely an appendage of the olfactory bulb, while in mammals it is responsible for most of the functions of the central nervous system. In human beings, the cerebrum is extremely large, to the extent that it covers most of the diencephalon and midbrain. In allometric growth studies of the brain capacity of various species, a line of continuity is apparent from mice all the way up to whales. This enables us to make conjectures regarding the evolutionary process of the central nervous system. In particular, the highly developed forebrain of human beings (which later differentiates into the cerebrum and diencephalon, or interbrain) is very interesting due to its large size and the functions for which it is responsible.

The same thing can be said of a cherry tree. That is, a single seed grows into a trunk, branches, foliage, and flowers, to form a tree. Of all plants, the cherry tree in particular responds to the outside world by putting out buds, then flowers, then produces green and finally red foliage in accordance with the changing seasons and years, which is very similar to how the human cerebrum functions.

5.2 The relationship between form and function

The outside world provides stimuli that our sensory organs take in and respond to. For
example, a sound stimulus is responded to by a hearing organ such as the vestibulocochlear nerve; a light stimulus is responded to by the eyes, the retina, and the optic nerve; and the warmth produced by light is felt by the skin. When the brain recognizes things in the outside world, as well as the various matters that arise within the mind, it recognizes both the form of the thing as it exists at that moment in time and the functions that will arise from the changes that the form will undergo. Function is a phenomenon that is tied to changes in form. For example, our eyes recognize a cherry tree as a form. Changes in this form take place so slowly that we cannot recognize these changes as functions. However, because we have a stored memory of the changes in the cherry tree’s flowers (i.e., the fact that they are in full
bloom for a very short period of time, after which they all fall to the ground), when we see the cherry tree in full bloom, in an instant our brain recalls the changes it will undergo. Thus we are made aware of the transience of the life of the cherry blossoms.

Our senses of sight and touch can recognize the form and function of what we are seeing or touching; however, sounds, smells, and flavours are invisible. Thus the brain cannot directly recognize their form through our remaining three senses of hearing, smell, and taste. However, it can recognize their function, and finally, through those functions, the brain isable to grasp the form. This is why we are able to reproduce in our memory the forms and functions of things we have seen, sounds we have heard, or scenes or situations that have made an impression on us. Stimuli from the outside world are instantaneously converted into electrical signals at the various sensory organs throughout the body, and these signals in turn activate the respective nerve cell networks of the organs able to respond to the signal. The signal is then recognized by the nerve cell network of the brain as a whole. This influences the differentiation of nerve stem cells and becomes a new memory. Due to this endless process, our brain can reconstruct what we are not actually seeing, hearing, tasting, or touching as if it were reality.

5.3 The role of time

When it comes to our self-awareness, we are not aware of any changes as they happen; it is asif every moment is the same as the last. However, just like the cherry tree, our brain keepsdeveloping. A group of neural stem cells in the cerebrum continues to respond not only tochanges in its environment but also to our previously extant memories, which are based onthe flow of time. Therefore, time is an extremely important factor in recognizing the flowfrom past to future in the huge number of memories in the mind.

A newborn baby sleeps almost all the time. When it gets hungry, it wakes up and cries, is fed milk by its mother, quietens, and goes back to sleep. A baby’s life consists of repeating this daily cycle of short periods of wakefulness and long periods of sleep. During this earliest period, the baby’s brain and sensory organs are immature; it cannot yet clearly distinguish between its self and non-self. However, after this earliest period of infancy, as the eyes and ears develop, the baby gains the ability to recognize (reconstruct) the outside world inside his or her brain, even without the input of information from the outside world. Further changes occur as the cerebral cortex rapidly develops, and the baby is now awake for longer periods
of time and can better recognize its external environment (the outside world). It also begins to recognize itself (self-consciousness). Thus, with this clear division between how wakeful periods and sleep periods are used, new memories are accumulated in the brain with the passage of time, while unnecessary memories are discarded.
Recognition of the sense of being alive has at its foundation the so-called time factors of past, present, and future. In nature and society, on the other hand, there exists the time factor of history, which is based on the passing of months and years. On the basis of this factor, we recognize the four distinct seasons in Japan, through which the cherry blossom tree proceeds in its growth cycle. Thus we see that our memories are linked to concepts of date, time, and season.

5.4 Self-consciousness

The brain, like the other organs, develops to completion in the womb. Immediately after birth,the brain has no consciousness and of course cannot recognize itself or anything else. However, with stimuli from the various sensory organs, the brain continues to develop and byaround the age of three years, it can recognize its own existence. In short, it is able torecognize its self, or ego (oneself). This self is based on the new memories that the brain creates by what it takes from what is around us (the outside world) and what it obtains from thinking of intangible things (the interior world). This is what is known as self-consciousness. This process is basically no different from the process of the cherry blossom tree. Every year the cherry tree puts out an abundance of buds, from which sprout twigs. Of course, not all of these new twigs remain; some are broken, cannot grow, and fall off the tree. This is how a cherry tree ages, and the tree form changes. Self-consciousness develops when the sensory organs, located throughout the bodyrecognize the outside world and send information that is deemed important to the group of undifferentiated neural stem cells in the brain. This information is then compared with the fundamental memories (the self or the ego), and the brain creates new memories (the neuron network). Even with our eyes closed, we can picture an imaginary scene that appears real to us, because these neuron networks, which continue to work and develop every second,
become what we could call a ‘momentary self’, search for old memories stored in the
network, and display them in the mind’s eye. The cherry tree, of course, does not have a neuron network like that of the human brain. Instead, its self is its countless meristematic cells, which all differentiate and develop according to their environment.

The phenomenon of dreaming?i.e., seeing images in the brain while asleep despite theabsence of information from the outside world?can also be explained in this way. By combining various memories, the brain is able to create an internal scene that we think we are seeing and compare it with previous existing memories. The act of thinking is basically making judgments based on a comparison between the world that surrounded you in the past and that which surrounds you in the present. At the time in question, we tend to always believe our judgment is correct; however, with the passage of time, we often come to reconsider our original decision. In short, we are constantly recognizing things anew. The decision we made at that time, or what we thought at that time, is accumulated in the brain as memories. It is believed that this mechanism of self-consciousness is a function of the cerebrum, which has developed enough to reproduce and recognize many versions of our self.

5.5 Intuition

An infant, even though it is not able even to talk, discriminates events around it and responds to them with intense curiosity by smiling endearingly or crying loudly. It is thought that it is during this stage that neural stem cells differentiate most actively in a person’s lifetime. At this time, of course, knowledge based on scientific principles and so on is unnecessary; the infant’s brain develops simply via the process of intuition developing into mind, just as the cherry tree does.

Intuition is the keen and instantaneous feeling we have towards even the smallest of stimuli, without thinking deeply or imagining anything consciously. This is the most important element of the mind. Intuition is basically close to instinct, or our animal-like mind. What we take in from our intuition develops into a clearer mind?that is, our own intentions, or selfconsciousness? when the thought process proceeds further. The difference between the intuitions of the brain and cherry blossom tree lies in the dissimilar characteristics of neural stem cells and meristematic cells. What is essential to understand is that the intuition that the brain shows regarding the changing seasons is neither inferior nor superior to the intuition displayed by the meristematic cells of the cherry tree.

There is a theory that in ancient times?before calendars existed, when the seasons were not yet clearly defined?people managed their agricultural activities by observing cherry trees. When they saw the cherry trees in full bloom on the mountainside, they could determine when it was time to plant rice seedlings or how much harvest they could expect in the autumn.

We are not born with a distinct self-consciousness. We are completely dependent on theperson who rears us for the lifelines of nutrition, temperature regulation, protection fromoutside dangers, and so forth. During this early period, the mind is not yet among the brain’sfunctions. With time, the body grows; however, if an infant does not receive stimuli or information from the outside world, the mind cannot arise spontaneously within the brain, based on things that the infant has never seen or heard. The mind develops to completion by obtaining knowledge, acquiring techniques, and learning the ability to be independent as an individual. It takes as long as twenty years for the mind to grow into that of an adult member of society.

There are some expressions frequently used in Japanese such as ‘having a heart’, ‘having no heart’, and ‘having a good heart’. It is safe to assume that these expressions come from the fact that, from the birth of human society to the present day, humans have always depended on one another. In short, our minds develop on the basis of our brain’s memories of individuals, society, and nature. Indeed the mind itself is proof of a person’s having been raised in human society. The above expressions indicate that human beings recognize that,
for us to live in nature or in human society, we need to follow the proper rules of mutual reliance, the rules of nature, and the moral codes of human society.
The human mind is made of inherited memories that have accumulated in the long and difficult history of human mutual dependence and of human dependence on nature. The Japanese expression o-tagai-sama (we are both of equal status in this regard) symbolizes the desire to settle issues calmly, through compromise and mutual understanding. This is wisdom that has been cultivated over the history of human society?it is not easily dislodged. The brain, with its huge capacity of memories, can acquire a mind unfathomably rich in wisdom, built on the basis of human interdependence and mankind’s dependence on nature. With this wisdom as a foundation, the brain not only preserves its own existence but also keeps on
learning and developing as it makes careful choices to preserve its own existence.

In summary, the mind is not included in our genetic information. If cloning technology advances sufficiently, it would be possible to create a human in a short period of time bysimply copying the genes of cells. However, to create a copy of a human being with exactly the same mind as the source, the copy would have to spend exactly the same length of time alive and be raised in exactly the same environment in which the source was brought up. In short, it would be impossible.


Until now, we have long believed that an affluent society can be created on the basis of scientific ideas. At present, however, regardless of the scientific knowledge we havemanaged to accumulate, we are surrounded by changes in our environment?the problem of ageing societies, explosive increases in the world’s population, severe disasters, and so on? as well as other such unpredictable events that have created more complex and difficult problems for us to solve. If this situation continues, then distress and anxiety, worries about not being able to have a stable life, and a general feeling of despair will all undoubtedly increase because, behind the curtain of ‘scientific advancement’ and ‘scientific ideas’, there are problems we have either failed to notice or have avoided discussing, i.e., those problems that cannot be explained with science.

For instance, although it is true that we now live longer, we cannot avoid ageing. The number of elderly people hospitalized for treatment of health problems and anxiety is constantly on the rise. No means have been found to halt these fundamental changes. Life does not let us die easily. Neither science nor medicine has managed to show us a way to adapt to today’s super-ageing society?a phenomenon that we are experiencing for the first time as a species. They tell us nothing about how we can live a peaceful, easy life.

What we must not forget is that there are limits to human abilities and that humans have managed to live in nature by depending on our intuition and mind. The scientific way of thinking only focuses on the benefits to be gained through comparative research; modern science does not place great importance on dealing with difficult and/or unexpected problems. I wonder if the side effects of the issues that have been marginalised will not become more and more apparent in coming years. Furthermore, people have accepted so-called scientifically based ideas, calling them ‘proven facts’, even though they have not confirmed them for themselves. Moreover, depending on their requirements, people interpret these scientifically based ideas in different ways. This leads to the discussion branching off in multiple directions, taking on an uncontrollable life of its own.

So what does the advancement of science really mean to us? Is it absolutely necessary for human happiness? If it is necessary, then to what extent? Are we sure there aren’t some serious hidden disadvantages behind the initial advantages? Has the interpretation of conventional science and its direction thus far been stretched, and has now slipped into selfcomplacency

To answer these questions, I believe that we need to consider in turn the following ones. What is the mind that we have been given? How can we fulfil the mind? What did our ancestors think about the difficult problems of life, and how did they overcome them? We must as individuals also recognize the problems we have caused in nature and society, and not be afraid to express them. If we live without fearing failure, recognizing our own individuality in the midst of the workings of nature, and recognizing the role we have to play, then perhaps we can eventually achieve happiness.

When I see patients in my consultation room, I realize that, for human beings, not only the symptoms of the body, but also the condition of the mind that lies behind those symptoms, is important. If I can help someone to lead, in his or her own way, a principled, enjoyable life by helping that person to understand the questions, What is the mind?, What is the self?, How does the mind arise from the brain?, and Why is the mind necessary?, then I would feel very privileged indeed.


 投稿者:永井哲志  投稿日:2013年 1月26日(土)11時03分27秒


             南大谷クリニック 研究紀要 2012       著者 永井哲志

3.心とは? ―― これまでの脳科学によるアプローチ
3.1 心はどこにあるのか?
3.2 心理学による心の解明
3.3 脳科学による心の解明
3.4 脳科学の問題点
4.1 神経幹細胞の存在による新理論
4.2 脳の神経幹細胞と桜の生長点細胞
5.1 -脳の発生過程からの推測-
5.2 形態と機能
5.3 時間の役割
5.4 自己意識
5.5 直観




 人間の生命の営みと、植物例えばその象徴的な桜の木「バラ科バラ属の落葉広葉樹林であるサクラ」(以下、桜と呼ぶ)の成長には、同じ生物として「細胞から細胞へ分化し続ける」という共通する生命現象が存在する.桜にも自己を認識し環境の変化に対応できる、脳と似た仕組みがある.それは根や茎の先端にあって、活発に細胞分裂を行い、新しい組織を作るもとになる「生長点細胞」である.植物である桜には、外界の刺激に対して同時に相反する思考や反応を生み出す脳のような器官は認められないが、この無数の「生長点細胞」の分化によって、移り行く季節に合わせて、つぼみから花や葉、枝へと、1 本の木としてみごとな成長を遂げていく.
 近年、大人の脳の中にも、植物の生長点細胞と同じような働きをすると考えられる神経系に属する各種の細胞になることはできるがまだ細かく分化を遂げていない「多様性」をもつ「神経幹細胞」が見つかったことによって、「高等動物の成体の脳ではニューロンの新生は起きない」というかつての常識が覆されてしまった(Gerd Kempemann、Fred H.Gage 1997).この新たな「神経幹細胞」の発見は、脳も植物と同じような成長の仕組みで活動している可能性を示唆している.これは、これまでの脳科学的手法とは違った素朴な思考からも、複雑で難解とされてきた脳の働きの解明が可能になったことを意味している.心の理解は人類に残された最大の課題といわれているが、原理的にも最も困難な課題の1つであり、従来の科学的な手法に固執しているだけでは大きな進歩は望めない.本論文は、脳の働きの説明にこれまでは用いられなかった植物の「生長点細胞」と脳の「神経幹細胞」とを対比した理論を用いて、「どのようにして脳から心が生まれるのか?」について直観的に考察した.




3.1 心はどこにあるか?

 「心とは何か? どこにあるのか?」という疑問は、文明の発祥以来、人間になげかけられてきたものである.6千年前のエジプトでは、「心の座は心臓にある」という考えが生まれていたし、4千年前のバビロニアでは「肝臓にある」とされていた.より体系的な学問が芽生えたギリシャ時代には、「脳または心臓の働き」が心を生むとされた.
 たとえば、医学の祖とされるヒッポクラテス(Hippocrates 前460?~377?)は、心は「脳の営み」だと考えていたし、哲学者プラトン(Platon 前428 頃~347 頃?)は「脳と脊髄にある」と唱えていた.一方、プラトンの弟子であるアリストテレス(Aristoteles 前348~前322)は、「心は心臓にある」と考えた.
 アリストテレスの思想はヨーロッパでは大きな影響力を持ち続けたので、長い間「心臓が心の座」と考えられてきた.ところが、17 世紀に現代科学の方法論が生まれると、「脳」がふたたび注目されるようになった.たとえばフランスの哲学者ルネ・デカルト(Ren?Descartes 1956~1650)は、心や意思の源は、「脳」、なかでもその奥深くにあって「目の神経とつながって光を感じ、ホルモンを分泌する松果体」に存在すると主張した.また、2世紀に活躍した古代ローマの医師ガレノス(Galenos 130 頃~200 頃?)は解剖学の研究に努力して、「精神の働き」は脳の実質に在るのではなく、「脳屋」という脳の内部の「脳脊髄液のたまっている空間にある」と考えた.
 その他にもいろいろな考えがあったが、17 世紀以降は、「心は脳と関係がある」という点では大差がなくなった.違いがあったのは、その「関係」についての考え方で、大きく分けて一元論と二元論の2 つがあった.一元論では、「心は脳の活動と同じもの」であり、同じ過程を別の言葉で表したにすぎない.一方、二元論は、「心」と「脳」は別のもの、別の過程であって、「心は脳から独立している」という考えだった.
 これらの考え方はまさに根底から異なっていたので、長い間対立が続いた.優勢だったのは二元論で、これは二元論が宗教、とりわけキリスト教の説く考えと矛盾しないためだった.実際、18 世紀に一元論的な考え方を表明したフランスの医師デラメトリ(Julien Offroy de La Mettrie 1709~1751)は、主として生理学の力を借りて、人間の精神活動は脳という物質の働きにほかならぬことを論証したが、それが発表されると宗教界に激しい憎悪の嵐がまきおこり、亡命を余儀なくされた.

3.2 心理学による心の解明

1879 年にドイツの生理学者・哲学者ブント(Wihelm Wundt 1832~1920)が
ライプツィヒ大学にはじめて心理学教室を創設したときにはじまる.しかし、内面的世界で生じるさまざまな現象は漠然としていて、直接、客観的に測定することは難しい.そこで心理学では、客観的に、外から測定できる行動の研究を通して、内面の心理的精神的な過程を明らかにしようとする.学習、記憶、知覚、認知といった行動について、内に潜む心的過程と外に現れる行動との関連性について考えるとともに、実験や観察といった方法で研究している心理学では「心」を使わず、「反応」という言葉を使う.そして、人間の誕生から死にいたる生涯全体に及ぶ生の営みを、心の働き、その行動へのあらわれ、そしてそれがもつ人間的意味という3つの面からとらえようとして、心を多くの成分に分けて考えたが、近年、そのうちいくつかの成分については、脳との関連が脳科学による研究法の発展により明確になった.だからといって、その数々の成分を根底でつかさどっている中心の成分、生命を与えている根源そのものと考えられていた「自我(self)(ego)」または「魂(a soul)(spirit)」、あるいは「自分自身(my self)」とは何であるかは、やはり説明できてない.

3.3 脳科学による心の解明

1791 年、ドイツの解剖学者・医師ガルヴァ-ニ(Luigi Galvani 1737~1798)がカエルの脚を使って動物電気を発見し、神経伝達機構の究明の道を開いた.また、イギリスの化学者・神学者プリ-ストリ-(Joseph Priestley 1733~1804)らは、革新的な実験法を開発し、空気中の酸素の発見をはじめ、さまざまな気体を分離するとともに、体内の熱は化学反応によって生じることを発見した.1774 年、プリ-ストリ-はフランスを訪れ、空気の成分を発見したことをフランスの化学者ラヴォアジェ(Antoine Laurent Lavoisier 1743~1794)に説明した.ラヴォアジェはただちに、目に見えないようなものでもさまざまな物質で構成されていることの重要性を発見し、近代化学の確立につながる化学革命へのきっかけとなったのである.体内の熱発生の要因とされていた霊的存在、プネウマはこの化学革命によって、完全に否定されることになった.
 脳の研究もこのときを境にして、近代生理学の形成期と足並みをそろえるように、大発展期を迎えるのである.イギリスの生理学者シェリントン(Charles Scott Scherrington 1861~1952)らの研究によって、ニュ-ロン部分では電気信号による伝達が行なわれ、ニュ-ロンとニュ-ロンの間にある接合部(シナプス部分)では、化学物質による信号伝達が起こるということが解明された.これは電気系と化学系という2種類の伝達機構を使用することによって情報を伝える、「情報伝達回路」(ニュ-ロン・ネットワ-クまたは神経回路と呼ぶ)としての脳の構造解明への足がかりを与えることになった.
 第2次大戦後、シェリントンの下で学んだカナダの神経学者で脳外科医のペンフィ-ルド(W.Penfield 1891~1976)は、脳手術にさいして大脳皮質の電気刺激に基づいた新たな「機能的局在論」を実質的に施行した際、患者の同意を得て大脳皮質の様々な部位に電極を刺し、電気刺激を与えて、その時の患者の様子を観察した.その結果、患者の頭の側面、耳の上のあたりにある領域は、脳科学に決定的な影響をもたらした.いわゆる「脳の局在説」という考えがその実験によって証明されたからである.
1958 年ヒュ-ベル(D. H. Hubel 1926~)とウィ-ゼル(T. N. Wiesel 1924
~)によって発見された、特定の刺激と特定の状況にのみ反応する視覚神経細胞の存在は、やがて80年代、90年代にさまざまな認識細胞の仮説を生む先べんとなった.物体像が視覚的に提示されると、私たちの脳にはそれぞれの物体像に対応した神経細胞の活動が起こる.その物体像の認識にいては、現在、大きく分けて2つの考え方がある.1つは、個々の物体像そのものに対応している特定の神経細胞があるという考え方である.機能局在を1 個の細胞レベルまで押し進めようとする立場である.この考え方に従うと、おばあさんの顔にのみ反応する「おばあさん細胞」が、おじいさんの顔にのみ反応する「おじいさん細胞」があるということになる.もう1つは、さまざまな図形特徴に対してそれぞれ選択的な細胞があり、これらの細胞の組み合わせによって個々の物体像が表現されているという考え方である.この考え方によると、それぞれの物体像は、その物体に含まれる図形特徴の組み合わせによって表現されることになる、情報表現は1 個の細胞のレベルまで必ずしも局在せず、複数の選択性の不完全な細胞の集合によって認識対象が表現されているとする立場である.
 1970 年から80 年代にかけては、コンピュ-タ-科学が爆発的な進歩を遂げた.その進歩と呼応するように、脳の精神活動とコンピュ-タ-の情報処理の仕組みを同じように考えることが次第に強くなってきた.この脳の一元論は、認知科学者デイビット・マ-(David Marr 1916~1998)の計算理論の登場によって決定的になる.マ-は、シナプスの情報伝達回路がコンピュ-タ-とまったく同じ働きをするという例を参考に、脳とコンピュ-タ-は同じ仕組みで説明できる可能性があるということを理論面から裏づけた.

3.4 脳科学の問題点

 脳の感覚過程における情報処理は、大脳皮質を構成する約140 億の神経細胞の活動によって行なわれているとされる.神経細胞は、それぞれシナプスで他神経細胞と結合しているが、大脳皮質全体のシナプスの総数は10 万×140 億個に達する.この超天文学的な数のシナプスが複合しながら無数の神経回路網を作っているのである.そして神経細胞は機械の部品のように固定されているのではなく、刻々と細胞分裂によって新しく生まれ変わっているので、神経回路も常に変化している.また、これら無数の神経細胞はみな同じ遺伝子をもっているが、それぞれ違った環境と時間で分化してでき上がっているので、神経細胞とシナプスをみな同じ単位とみなして積み上げても、脳全体の働きを説明することにはならない.したがって、どんなに努力して、ある1部位の詳細なメカニズムを解明しても、脳全体の機能である心を明らかにすることはできないというのが現実なのである.


4.1 神経幹細胞の存在による新理論

 人間の脳全体では数1000 億個以上の神経細胞があるとされ、その細胞の構築は電気的に興奮するニュ-ロンと、ニュ-ロンの活動、維持を助ける働きをしているその10 倍もの数の非興奮性細胞であるグリア細胞との網の目からなる.ニュ-ロンは普通の細胞とは違い、周囲から神経突起というものが多数伸びている.そのうちの一本は特に長く、軸索と呼ばれている.そして、ニュ-ロン同士の間をつなぐシナプスと呼ばれる構造で互いに連絡しあっていて、ニュ-ロンに発生する電気的信号は軸索や神経突起を通り、シナプスの化学物質を介して隣のニュ-ロンへ伝えられる.このシナプスを介するニューロンへの信号伝達網が、「脳の細胞組織の基本的な構造」(以下、ニューロン・ネットワーク組織と呼ぶ)となっていると考えられている.
 しかし1997 年、スウェ-デンのサ-ルグレンスカ大学病院のエリクソン
(PeterS.Eriksson 1936~)とソ-ク生物学研究所のゲ-ジ(Gage 1940~)らは、成長を終えた大人の脳(成人の脳)でも、少なくとも記憶と学習に重要な働きをしている側頭葉の内側にある海馬においては、ニュ-ロンが日常的に新生していることを発見した.またここ数年間で、その成人の脳の中にも、神経系に属する各種の細胞に分化を遂げていない未分化で多様性(その時点でどのような細胞になるのか決まっていない)をもつ「神経幹細胞」が見つかったことにより、「高等動物の成人の脳ではニュ-ロンの新生は起きない」というかつての定説が覆されてしまった.

4.2 神経幹細胞と生長点細胞




 心は脳からどのようにして生まれるのかを考える上で、その脳の発生と構成に関する基礎的知識をもつことは大切なことである.私たちの脳は1 個の受精卵から分化して膨大な数の細胞が形成される間に出来上がっていく.その1 個の受精卵はあらゆる臓器に分化できる能力があり、受精後およそ3 週目途中の
胎生期には、神経幹細胞があらわれ、胚発生の初期に脳は中枢神経系の幹細胞である神経上皮細胞が分裂と増殖を繰り返して、盲端になっている一本の管(くだ)(神経管)になる.その管の上端(頭側)の部分はやがて脳になる3 個の膨大部を生じる.これらを前から後へ前脳胞・中脳胞・菱脳胞である.前脳胞はさらに著しく発達して終脳はまた大脳となり、大きく左右に向かって膨隆し、そのおのおのが半球状を呈しているので、これを大脳半球という.中脳胞はあまり発達しないが、菱脳胞はさらに分化して橋・小脳・延髄の3 部 に分かれる.

5.2 形態と機能


 5.3 時間の役割


5.4 自己意識

 脳も他の臓器と同じように母親のお腹の中で成長して完成する.そして、出世時はまだ意識もなく、もちろん自分のことなど分からない.しかし、出生直後から様々な感覚器からの刺激で脳はさらに成長して3歳ごろ自分の存在を知ることになる.つまり「自我(self)(ego)」、あるいは「自分自身(my self)」を感じるようになる.その自分を基に、身の周り(外界)と実際にないものを思い浮かべること(内界)から感じ取ることができるすべての物事が脳の中で新たな記憶となって形成されていく.それが「自己意識」でる.

5.5 直観





 私たちにとって科学の進歩とは何か? 人間の幸福にとってどうしても必要
なのか? どこまで必要なのか? メリットの裏に深刻なデメリットが隠されてないか? これまでの科学の考え方、方向性はそれ自体が拡大解釈されて、自己満足に陥ってしまってはいないか?
 この疑問に答えるには、「私たち人間に与えられた心とは何か?」、「心を満たしてくれるものは何か?」、「先人たちは一生の難題をどのように考えてどのような心で乗り越えてきたのか?」などをよく考察し、一人ひとりが自然の中の自分自身と社会の問題点(困っていること)を正直に捉え、素直に表現する必要があるのではないか? 失敗を恐れず自然の営みの中で自分の個性を知り、自分の役割を考えながら生きていけば、やがては幸せを感じるのではないか?




 投稿者:永井哲志  投稿日:2012年 9月 6日(木)20時30分30秒
  心は脳からどようにして生まれるのか?    のキーワードで検索して頂きますと論文があります。




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  FIRTH PIERLAAIT(ファース ピアーライト)って




 投稿者: あだち  投稿日:2007年 6月 3日(日)13時43分11秒

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 投稿者:タマ  投稿日:2006年12月15日(金)12時19分5秒


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 投稿者:タマ  投稿日:2006年12月 3日(日)13時50分23秒
  精神波量子脳理論  「神秘体験」(弓月城太郎・作)より

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 また長い間不明とされていた記憶の「保存」と「脳内(及び脳外)での遍在性・全体性」の謎は、量子エンタングルメント とアハラノフ・ボーム効果、及び形態因果作用による時空間を隔てた相互作用により説明される。
 ではゲーデル命題を決定へと導く情報エントロピーの減少はどこからもたらされるのだろうか? そのためには「力の場」と「意味の場」の連続体について論じる必要がある。
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 ああ! 朝日が昇る。レース越しにエレガントな緑のシルエットが霞んで見える。世界は黎明の時を迎え、森羅万象は光の世界へと立ち返ってゆく。窓の外では小鳥たちが歌を歌い、神の子であるこの小さき私を祝福した。


 投稿者:タマ  投稿日:2006年11月18日(土)18時17分2秒
  来た! 来た! 来たー!! 超常現象の物理的メカニズムを解明したSF小説がついに発表された。


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蛇足 2

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