The Minder Brain

How Your Brain Keeps You Alive, Protects You from Danger, and Ensures that You Reproduce

Joe Herbert

• Publisher: WSPC
• Year: 2007
• ISBN:
  9789814338240
• Topic: Biological Sciences
• Subtopic: Neuroscience
• Index: Biological Sciences

Ambition, genius, thought, imagination, love, hate, greed and, above all, consciousness ourselves as alive and as part of our world — all this is somehow enabled by the brain. The brain is the person, and if it goes wrong, a person is ruined. This book is about part of what the brain does — a role of which many of us are hardly aware, but one that has ensured, the survival of mankind. Despite famine, drought, wars, cold, infections and hostile environments, we survive as a species — though not always as individuals. All this time, our brains have been coping with what fate throws at us — a process that some call adaptation. How does the brain do it? How does it know what's needed? How does it enable us to provide that need? How much do we depend on our own brains, or on those of others?

This book is different from other books on the brain. It deals with the brain's role in survival, rather than “higher” cognitive functions (such as language or thought). It describes the special part of the brain that keeps you alive: that makes you feel hungry when you need energy, makes you feel thirsty when you need water, drives you to reproduce so that your species survives, makes you fearful of things or individuals that might harm you, and defends you against adversity.

Contents:

• The Brain as a Survival Machine
• A Chemical Code for Survival
• Serotonin, Steroids and Signalling
• The Brain and Stress
• The Weight-Watcher in the Brain
• Staying Wet and Salty
• Keeping Warm, Staying Cool
• The Sexual Brain
• Bonding, Motherhood and Love
• The Brain Goes to War
• The Rhythm of Life
• The Brain Breaks Down
• Individuality

Readership: A general level book that will interest both non-scientists and scientists from other fields.

Chapter 1

The Brain as a Survival Machine

This is Charles Darwin writing in 1859: “It is most necessary…never to forget that every single organic being around us may be said to be striving to the utmost to increase its numbers; that each lives by a struggle at some period of its life; that heavy destruction inevitably falls either on the young or old…. Lighten any check, mitigate the destruction ever so little, and the number of the species will almost instantaneously increase to any amount. The face of Nature may be compared to a yielding surface, with ten thousand sharp wedges packed close together and driven inwards by incessant blows…”. This book is about how we use our brain in this struggle for existence. It is about how parts of our brain, inherited from our mammalian ancestors, are dedicated to make sure we survive, although we are hardly aware of them; and about how these work together with more recently acquired brain structures to guide us through life, keeping us safe and sound for the most part, so that we pass our qualities on to succeeding generations.

You, like everyone else, have a warm, soft, rather moist, body, needing regular intakes of usable energy. You are here because your parents had the will and opportunity to reproduce. But you live in a tough world. Food, water and essential minerals like salt are not easily available in the environment from which you originally evolved. You have to want them and to know where to look to find them. You have to keep warm in the cold, or keep cool if the weather gets too hot. You have to find a mate, if you are to pass on something of yourself to succeeding generations. Your ancestors will have had to avoid being eaten by another species, whilst making sure that they themselves were effective predators. You are in competitions for many of the things you need, including a mate, with others of your own kind. To survive, you have to adapt. That is, you need the means to mould your behaviour to take account of how your world is, and to change your behaviour when it changes. Some of these changes may be sudden, others slow. Some arrive without warning, others are more predictable. Adaptation means not only changing your behaviour. Your body needs to adapt as well, making sure that it tells you what it needs to keep you going, and that it is resilient at moments of difficulty or shortage. So you survive into better times. No matter that you now live in a world we think of as technologically advanced. No matter that there are some who think that the modern world has removed some of the selection pressures on humans to which other animals are customarily exposed—true, if true at all, for only a small segment of humanity. You still carry with you many of the features that made your ancestors such a success. Otherwise, you would not be around today. The very fact that these qualities are now used in circumstances hardly imaginable, even a few centuries ago, is a tribute to your adaptive capacity.

Your brain not only keeps you alive, well and—as far as it can—out of danger, it also enables you to deal with life's emergencies. This may be a period of food shortage, or dehydration, or intense cold, or a confrontation with a larger, stronger rival, or the demands of giving birth or rearing young or preserving a territory, escaping from danger or keeping down a difficult job or coping with a bereavement. Such a demand may be short-lived and sharp; it may be long and unremitting; or intermittent and unpredictable. A general name for such an event, or set of events is ‘stress’. Actually, a better word is ‘stressor’, meaning some external or internal event that induces ‘stress’—the state of demand. Stressors can arise from the physiological world—too little food, too much heat and so on—or from the social and psychological one—a fight, arguments with friends, an unsatisfactory relationship, a demanding job. These are all examples of the need to adapt, and adaptation needs a brain. We will discuss stress more in Chapter 4.

This book is about the role of the brain in everyday life—adapting to intermittent emergencies such as stress. Modern ideas on adaptation began in the 19th century. Claude Bernard, like many other great scientists, is known for only a little of what he actually did. He was particularly interested in digestion, and worked on the way that the liver converts fats and sugars such as glucose in the food to glycogen, a form in which energy is stored. He recognised that the body needed to maintain levels in the blood of important molecules like glucose despite the fact that they were not always available. Hence, his dictum which resonates down the centuries: a constant internal environment is the condition for free life (La fixité du milieu intérieur est la condition de la vie libre). You walk around an inconstant, unpredictable and often unsatisfactory world carrying your own private, much more consistent, world with you—the inside of your body. But you have to keep it that way, despite the buffeting it gets from the outside world, a process now called ‘homeostasis’. Some great scientists, like Bernard, tend to be resistant to the ideas of others—in his case, those of Darwin. Bernard was a ‘generalist’: he was interested in general properties of the body, not with individual differences. This does not detract from the stature of Darwin, who was fascinated by the importance of individuality, and showed how small variations in an individual's characters (a longer leg, a sharper claw, a less obvious colour etc.) might make it more or less ‘fit;’ that is, change the odds ever so little for or against its favour when conditions became tough. Not only were physical features important: slight advantages in the ability to communicate, to be a more effective parent, to learn a new skill, or to recognise a dangerous situation were all part of the Darwinian theory of selection. These abilities depend upon a brain. So, too, does the ability to know when to use your sharper claw to attack, or run away on your longer legs, or to summon help from those whom you know may offer it.

Social and Physical Evolution

Owing to the struggle for life, variations, if they be in any degree profitable to the individuals of a species, in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by the offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are born, but a small number can survive. I have called this principle, by which a slight variation, if useful, is preserved, by the term ‘natural selection’, in order to mark its relation to man's power of selection. But the expression often used by Mr Herbert Spencer of the survival of the fittest is more accurate, and is sometimes equally convenient.

Charles Darwin. (1872) The origin of species. Sixth ed. Ed. R E Leakey (Hill and Wang, NewYork.)

In recent years, historians have come to see that the most far-reaching change which grew out of the Renaissance was the evolution of the scientific method of inquiry. They have, therefore, given to the period of growth in science between 1500 and 1700 a new name, the Scientific Revolution…. Butterfield…says…that it ‘outshines everything since the rise of Christianity and reduces the Renaissance and reformation to the rank of mere episodes’…. It was in the first place an intellectual revolution: it taught men to think differently. Only later was this put to a new practical use, in the Industrial Revolution about 1800, which gave our civilisation its outward character.

J Bronowski, B Mazlish. (1960) The western intellectual tradition. (Hutchinson, London.)

…A sense of genetic unity, kinship, and deep history are among the values that bond us to the living environment. They are survival mechanisms for ourselves and our species…. biological diversity is an investment in immortality.

Edmund O Wilson. (2002) The future of life. (Little, Brown and Co., London.)

To transform a weed into a cultivated plant, a wild beast into a domestic animal…to make stout, water-tight pottery out of clay which is friable and unstable…to work out techniques, often long and complex, which permit cultivation without soil or alternatively without water; to change toxic roots or seeds into foodstuffs…there is no doubt that all these achievements required a genuinely scientific attitude, sustained and watchful interest and desire for knowledge for its own sake. For only a small proportion of observations and experiments…could have yielded practical and immediately useful results.

C Levi-Strauss. (1962) The savage mind. (Weidenfeld and Nicolson, London.)

Some 10,000 years ago, certain human populations in the near east changed their way of life from that of hunting community to one based on the domestication of plants and animals…. The surplus food produced by the farmers could support large numbers of people, who could become labourers, artisans, soldiers, artists, politicians and scientists…. It should be emphasised however, that the change was wholly cultural; it took place far too quickly and too recently to be associated with biological changes in individuals.

D Pilbeam. (1970) The evolution of man. (Thames and Hudson, London.)

Darwin's contemporaries saw at once what a heavy blow he was striking against piety. His theory entailed the inference that we are here today not because God reciprocates our love, forgives our sins, and attends to our entreaties but because each of our oceanic and terrestrial foremothers was lucky enough to elude her predators long enough to reproduce.

F C Crews. (2001) New York Review of Books.

On their journey through time, everyone brings their individual qualities, which may give them an advantage over others, or at least an increased chance of dealing with the exigencies of their uncertain world. In the terrible siege of Leningrad (St Petersburg) in 1942, between 600,000 and 1 million people died of cold and starvation. But some survived. This was not a random event. Though no doubt chance played a part, other factors tipped the balance between who would live and who would die. Much would have depended on the brain, whose ability to adapt to demands varies from individual to individual, and from time to time, within the same person. This, as we shall, see, is as critical a factor as any other in success or failure, and in determining the cost that even success may entail. Darwin showed us that studying physiological or behavioural control systems, important though this is, is not enough: we also need to know about how they vary between individuals, and how individuals thus vary in their effectiveness to deal with demand.

The brain is not a simple or uniform structure, so we have to ask whether there are parts of it that are more concerned than others with the story I want to tell. To answer this is not as easy as you might think. Suppose that you wake in the middle of the night, and feel hungry. You reach out a hand to turn on the bedside lamp. You get out of bed and put on a sweater. You walk downstairs quietly, so as not to wake others, go into the kitchen, open the door of the fridge and look for something to eat. You select a piece of cheese. Then, you scan the tins of food on the shelf above the fridge, reading the labels. You see one that you fancy and open it with a can-opener. You put it all on the plate, sit down and eat, though you find you have eaten enough before all the food has gone. So you store the remainder in the fridge for tomorrow.

You have just performed an adaptive response: you have defended your body against a too-low blood glucose—though you had no idea that this was the underlying cause of your behaviour. During the series of actions that make up your response, a large part of your brain has been used. It has detected the fall in your blood glucose levels. It has woken up. It has generated the sensation of hunger. It has motivated you to get food. It has decided to go and find some, and has remembered where food is to be found. It has allowed you to feel the light switch. It is also responsible for your knowing what a light switch is. It has recognised that as you get out of bed you are getting cold, and remembered that putting on a sweater can counteract cold. It has enabled you to perform the rather complicated actions of actually putting the sweater on. It has enabled you to walk downstairs without falling over. It has remembered that there are others asleep, and that is it anti-social to wake them—that is, there will be social repercussions (cost) if you do. It has recognised a fridge. It has also recognised a food object. Your brain enables you to read, and to translate what you read into food. That is, you know from the symbols on the tin—also recognised as such by your brain—that inside is a certain sort of food. The skill of opening a tin is only possible because your brain enables you to do so. You eat, using motor patterns generated by your brain. Signals from your body go to your brain, telling you when you have eaten enough. Your brain recalls that food is costly, and that there are means of preserving it for later, and that you will be hungry again quite soon. A great mixture of what psychologists would call motivation, emotion, memory and cognition, and what neuroscientists would call sensory and motor function. Does this mean that to understand the role of the brain in adaptation, we have to discuss everything we know about it?

Open thy mind, the truth is coming; know,
When the articulations of the brain
Has been perfected in the embryo,

Then the First Mover turns to it, full fain
Of nature's triumph, and inbreathes a rare
New spirit, filled with virtue to constrain

To its own substance whatso active there
It finds, and make one single soul complete,
Alive, and sensitive, and self-aware.

Dante. The divine comedy. II. Purgatory. Canto XXV. Translated by D L Sayers. (Penguin Books, Harmondsworth.)

All that is noble and excellent and all that is worst in human commerce has been thought to derive from the brain, a sort of gland that secretes lofty ideas and superior morals when healthy and oozes destructive plans when diseased.

F Gonzalez-Crussi. (1986) Notes of an anatomist. (Picador, London.)

Killer instinct. General use, to describe the quality of extreme seriousness thought to be required to win in sport and life.

Nigel Rees. (1996) Dictionary of cliches. (Cassell, London.)

Nature, that fram'd us of four elements
Warring within our breasts for regiment,
Doth teach us all to have aspiring minds:
Our souls, whose faculties can comprehend
The wondrous architecture of the world,
And measure every wandering plant's course,
Still climbing after knowledge infinite,
And always moving as the restless spheres,
Wills us to ware ourselves and never rest,
Until we reach the ripest fruit of all,
That perfect bliss and sole felicity,
The sweet fruition of an earthly crown.

Christopher Marlowe. (1564–1593) From: Tamburlaine the great.

…The intellectual, to my mind, is more in touch with humanity than is the confident scientist, who patronizes the past, over-simplifies the present, and envisages a future where his leadership will be accepted…. It is high time he came out of his ivory laboratory. We want him to plan for our bodies. We do not want him to plan for our minds, and we cannot accept, so far, his assurance that he will not.

E M Forster. (1951) Two cheers for democracy. (Edward Arnold, London.)

Fortunately not. This is because we know that parts of the brain are specialised for particular functions. For example, there is a complex pathway in the brain, starting at the eyes and responsible for vision. This is the visual ‘system,’ and it enables what we call ‘seeing’. Another set of nerve cells and pathways enable us to move. The arrangement of the motor system, as it is called, is rather distinct from the visual one, so that damage to it (for example, following a stroke) can cause paralysis—loss of movement—without blindness. Yet another part of the brain takes the information received by the sensory pathways and uses it to form an imprint, which we call memory. Next time we see, or hear, or feel the same sensation, we may be able to recall having experienced it before. Even more complex functions, like recognising a particular friend (or a fridge), or being able to read, are the responsibility of other parts of the brain. Damage to any one of them will interfere with that function, leaving others intact. These parts of the brain may be used for adaptive purposes (as in our night-time scenario) but they also have other uses. ‘Seeing’ is what the visual system does: you ‘see’ for many reasons, one of which is to be able to adapt. But the visual system is not a dedicated adaptation system: it does not tell you that you need to adapt, or how to do it: it provides the means (or part of them). You ‘move’ all the time; sometimes as part of adaptation, but for many other reasons. During the episode of your nocturnal feast, you used many of these parts of the brain. But many of them can be used in other, and quite different contexts. Later that day, you may play a game of tennis, or read your e-mail, watch television, or go to the office and write a memo. You will interact with colleagues and friends. You will use many of the same areas of the brain that were so useful during your midnight meal. None of these parts of the brain is dedicated to survival, though clearly essential for it.

But there is a brain system which has, as its main function, our preservation and that of our species. This part of the brain is particularly concerned with making sure that we do the things that maximise our health, keep us in good condition, and reproduce. As part of all these functions, it detects threats to our survival, recognises what they are, and devises the strategy by which we will overcome or compensate for these demands. It is clear that such an adaptation system cannot work on its own. No good being hungry or thirsty if you cannot move to where there is food or water, or recognise it when you see it. That means there must be co-operation between different parts of the brain, obvious enough. But none of these other systems has survival, adaptation and procreation as its ...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Dedication Page
• Foreword
• Contents
• Chapter 1 - The Brain as a Survival Machine
• Chapter 2 - A Chemical Code for Survival
• Chapter 3 - Serotonin, Steroids and Signalling
• Chapter 4 - The Brain and Stress
• Chapter 5 - The Weight-Watcher in the Brain
• Chapter 6 - Staying Wet and Salty
• Chapter 7 - Keeping Warm, Staying Cool
• Chapter 8 - The Sexual Brain
• Chapter 9 - Bonding, Motherhood and Love
• Chapter 10 - The Brain Goes to War
• Chapter 11 - The Rhythm of Life
• Chapter 12 - The Brain Breaks Down
• Chapter 13 - Individuality
• Author Index
• Subject Index