Your Brain and You

A Simple Guide to Neuropsychology

Dr Nicky Hayes, C. Psychol. FBPsS

Preface

This book is all about how our brains work to make us who we are. As research into the brain continues, we are discovering more and more about what parts of the brain do what, and how all those various parts connect together. It’s not simple: what we do, think, say and feel comes from many different brain areas all working together. Somehow, these areas work in concert to make us who we are. But that doesn’t mean that we are only a collection of nerve impulses. Our brains affect what we do, but what we do can change our brains, as well. Who we are, as people, is to do with the choices and decisions that we make in our lives. What we are exploring here is how our nerve cells and brain structures make those choices possible.

Another aspect of modern brain science is that it teaches us about neurodiversity, that is, that everyone is different. Each brain is slightly different, we all have different talents and skills, and sometimes a set of characteristics that we think of as ‘normal’ might actually be quite uncommon. You’ll read about how one area of the brain can be doing something while another area simultaneously does something else. But it’s important to remember that such simple descriptions are never the full story: brains can change; established pathways can be interrupted and regrow using different cells; some people are born with brains that do unusual things; and none of us is identical. But we are all marvellous! Our brains are amazing, and I hope this book will help to show you just how amazing they are.

Nicky Hayes

1

What is the brain?

In this chapter you will learn:

•  how the human brain evolved

•  the elements of the basic brain

•  how the thalamus and the limbic system work

•  the function of the cerebrum.

What makes human beings special? People have put forward any number of answers to that question. They have suggested that it is our ability to tell stories, to work together, to store information, to laugh, to imagine, to use language, to learn or to solve problems. It has even been suggested that we are distinctive because we are not really distinctive: we don’t have specialized horns, teeth, other natural weapons or the ability to run fast, and although we can do a lot of physical things, there are almost always other animals that can do them better. So because we are not particularly specialized in terms of our physical abilities or attributes, we have to work out different ways of doing what we need to do.

Any or all of these may be true. But underlying them all is the one thing which makes it all possible: the very special brain that human beings have evolved, and the way that it allows us to interact with our worlds – our physical worlds, our social worlds and our imaginary worlds. That brain is something very special, and it is what allows human beings to be what we are.

Figure 1.1 The human brain

Our brains allow us to see things and make sense of what we are doing. They allow us to take action: to move purposefully and do things when we need to or want to. They allow us to hear: to interpret vibrations in the air, to identify where they are coming from, and to identify their likely cause. They do the same for all of our other senses, including the sense receptors we have inside our bodies, which tell us what our muscles and joints are doing. Our brains make it possible for us to locate ourselves in the material world: to receive information from it, and to act within it.

But they do much more than that. Our brains also allow us to remember things – and in more than one way. They store conscious memories, like PIN numbers and addresses, but they also allow us to remember things that happened in the past, and even allow us to remember to do things in the future (most of the time!). They allow us to store skills, so that we can perform actions or cognitions smoothly and without consciously thinking about the steps involved; and they store patterns and meanings, so that we can make sense of new things that we encounter. They even allow us to imagine things that might happen in the future – or things that might never happen.

As social animals, it is important that we are able to recognize people, and it is our brains that allow us to recognize faces and bodies, and to distinguish between familiar and unfamiliar individuals. Our brains also make it possible for us to develop the attachments and relationships that are the basics of social living and to communicate with other people, using words, signs or symbols. At a more abstract level, our brains also make it possible for us to deal with the ‘three Rs’ – reading, writing and arithmetic, each of which involves distinct areas of the brain. But being human is more than just having mental skills of this kind: it is our ability to empathize with others which really makes us human, and our brains also provide us with the mechanisms for self-knowledge, identification and empathy.

We have emotions, too, and these are only possible because of how our brains have evolved. We feel anger, fear, happiness and disgust, we feel pleasure and pain, and we respond to rewards. We have times when we are alert and agitated, times when we are relaxed or experiencing states like mindfulness, and times when we are asleep. These states of consciousness are part of how our brains work. And, as human beings living modern lives, we also make decisions. The human brain is able to cope with decisions at various levels, ranging from deciding to sip a coffee to deciding to buy a house. The brain is an amazing structure, and in this book we will be exploring all these aspects of how it works.

How did the brain begin?

How did our brains become so complex? Back in evolutionary history, the first animals didn’t have brains at all. They were simple, one-celled organisms, a bit like the amoebae of today, which float in their liquid environment and absorb particles of food as they come across them. As more complex animals developed, one of their advantages was that they became able to detect nearby sources of food. They began to develop specialized cells that could identify the chemical changes in their environment produced by nearby food; and other cells that would help to propel their bodies towards it. They also developed a central linking system, which allowed them to use the information they were receiving and direct their movement accordingly. That central linking system acted as a co-ordinator between the incoming information and the resulting action.

And that was the beginning of it all. The first nervous systems were a simple, ladder-like network of fibres through the body, linked to a simple tube – which we call the neural tube. There’s something similar in the bodies of modern-day planaria, or flatworms. It’s basic, but we know it works because they still survive today. As animals became more complex, so did the structure of the nervous system. The front end of the neural tube began to become enlarged: it was the co-ordination centre which received information from the detectors that identified possible food, or light, or other information like vibrations, which implied that something large was nearby. Those detectors eventually became the sense organs, and the enlarged front part of the neural tube became the brain. The rest of the tube, which passed along the body, became the spinal cord, and the cells that passed information to and from it became the somatic (bodily) nerves. But even though it became so much more elaborate, it was, and still is, a kind of tube. It just has many more knobbly bits on the end than a flatworm has.

By the time of the dinosaurs, animals had become much more complex. That swelling at the front end of the neural tube had become a brain – not a very big one but one with different parts, which allowed it to co-ordinate the various bodily mechanisms needed to keep the animal alive, such as respiration, digestion and heartbeat. The brain also received information from the senses, which had become much more sophisticated, with their own separate organs and nerves and their own specialized parts of the brain. Movement and balance, too, had become vitally important functions, and a large part of the brain had developed to deal with these. And even a type of memory, although less complex than the memory we use, had begun to evolve. The dinosaur brain was tiny by comparison with our modern human brain, but, as palaeontology shows, it worked, and it worked very well. Dinosaurs dominated the land for many millions of years, and their descendants, the birds, are still with us today.

The same brain developments applied to other animals, like fish, amphibians and reptiles. Their adaptation to different ecosystems and food sources led them to evolve into all sorts of different creatures. Some of those ecosystems encouraged them to develop a highly sophisticated sense of smell, so the part of the brain dealing with smell became enlarged. Others required acute vision, which meant that the part of the brain dealing with vision became enlarged. Some animals developed an acute sensitivity to vibrations in the air, leading to an enlarged brain centre for hearing, and so on. As animals evolved to deal with their environments, so the brain evolved to co-ordinate that adaptation.

Another set of animals had appeared during the time of the dinosaurs: the mammals. These had evolved another special part of their brains, which was able to control and regulate their body temperature. As a result, mammals could be active at night and avoid the reptile predators that depended on the sun for warmth and energy. Mammals evolved in other ways, too: they began to suckle their infants and nurture them after they were born, which allowed the young animals a safe time to learn about the physical world around them and to explore. A small part of the mammals’ brain became specialized for adaptation and learning, so they were able to deal with unpredictable or changing environments. All this meant that when the world changed and the dinosaurs died out, the mammals were able to survive and take advantage of the ecological resources the dinosaurs were no longer using.

The mammalian brain, like that of other animals, adapted itself to the demands of its environment. Prey animals became highly sensitive to sensory information, developing acute reflexes enabling them to react quickly. Hunting animals developed in similar ways, as their survival required them to match the prey animals in order to catch them. Some animals were vegetarian, living only on plants; others were omnivores, exploiting whatever food sources they could find. And, most important of all, some of these lived socially, and shared their resources.

Since living socially was important, the demands of social interaction and co-operation meant that mammals lived in an ever-changing environment, so those parts of the brain that allowed them to deal with change and to communicate and pass on information became well developed. Animals living in social groups therefore developed multipurpose brains, which could adapt to different environments, interact with different individuals, spot new opportunities, and deal with problems. And in one particular group of mammals it became so important that it eventually overshadowed all the other parts.

When we look at a human brain today, almost all we can see are the two halves of the cerebrum: the part of the brain which we use for thinking, learning, communicating, deciding, imagining, and just about everything else which makes us human. The other, older parts of the brain are still there, but the cerebrum is so large that it has expanded to spread all over the rest. And since it’s the outer skin, or cortex, of the cerebrum which does most of the work, the cerebrum has become folded and wrinkled, so we can fit more surface area into the space. The human brain is one of the most remarkable things we know about, and understanding fully how it works is likely to keep our scientists busy for many generations to come.

The basic brain

In this book we’ll be exploring what modern neuroscientists have been able to find out about the ways that the brain functions. But even before we do that, we can learn a lot just from looking at the different parts of the brain and seeing how each part has evolved. Let’s begin by thinking about the most basic nerve functions a developing animal would need: to be able to move and to avoid pain.

This takes us back to the ancient neural tube. We still have the equivalent of it in our human central nervous system, although it’s become a bit more sophisticated since then, of course. It’s the spinal cord – the tube of nerve fibres running the length of the spine, linking our body’s nerve fibres with the brain. If we look at a cross-section of the spinal cord, we can see that it really is a tube: it has a hollow in the middle that is filled with a nutrient fluid. That hollow is surrounded by what we call grey matter, which is mostly made up of nerve cell bodies, and the grey matter is surrounded by white matter, which is nerve fibres carrying information to and from the brain. So the spinal cord is the main route for information going between the body and the brain. That’s why people who experience damage to their spinal cord can become paralysed. Their brains may be trying to get their muscles to move, but they simply cannot get the instructions through.

Figure 1.2 The spinal cord in cross-section

Not all movement is directed by the brain, though. The spinal cord also controls some of our reflexes – the rapid muscle movements that happen in response to painful stimuli. This is what happens, for example, if you pull your hand away from a hot surface. You do it quickly, without thinking, because the message of heat and pain only needs to go as far as the spinal cord. When it gets there the message is instantly routed to the nerve cells, which tell your arm to move your hand away. It doesn’t need to go all the way up to the brain. That’s known as a reflex and, because it’s such a basic survival mechanism, it’s controlled by the oldest part of the nervous system. What happens is that the message – pain, unexpected pressure, or whatever – is picked up by sensory nerve cells, which pass the information up to the nerve cells in the spinal cord. From there, a message is immediately passed on to motor nerve cells, which connect to the muscles and instruct them to contract. So you pull your hand away, or jerk your foot upwards, or respond in whichever way the reflex is appropriate.

The top of the spinal cord thickens out and begins to become part of the brain itself. The part where it thickens is known as the medulla, and if we think about it as the next part of the nervous system to evolve, we can see how it, too, is concerned with basic functioning. The medulla is the part of the brain that regulates basic bodily functions, such as breathing, swallowing, digestion and heartbeat – essential functions for all animals apart from the very simplest ones.

The basic brain is therefore a system that allows an animal to move, react to pain, eat, breathe and pass nutrients around its body. But if that animal is to survive in an increasingly complex world, it also needs to be alert and ready to move if something threatens it. Moving upwards from the medulla, we find that the brainstem becomes even thicker, turning into what is known as the midbrain, which is really a collection of several different parts. One of them is the reticular activating system (RAS), which regulates different states of alertness: sleep, wakefulness and attention. In humans and complex mammals, the RAS seems to be able to ‘switch on’ large areas of the cerebral cortex, so we are alert and paying attention to what is around us. It has some sensory pathways and many connections with other areas of the brain. When we think about its evolutionary origins, and how being alert would have helped an animal to survive in a dangerous world, we can see why this was quite an early part of the brain to evolve.

Figure 1.3 The structures of the brain

Other areas of the midbrain include the superior colliculi and the inferior colliculi (superior means above and inferior means below, which tells you how they are placed). These are oval structures which do some very basic sensory processing: the superior colliculi are particularly concerned with vision and touch, while the inferior colliculi are mainly specialized for hearing. They don’t connect directly with the higher levels of the brain. Instead, they have a direct connection with our attention and movement systems, alerting us immediately if there is, say, a sudden flash or bang. You can see how that would also have helped an animal to survive.

As the brain evolved, animals were also becoming more sophisticated in how they moved. Another part of the midbrain, the pons, is the main route for connections between the body and the cerebellum, which is the co-ordinating centre for smooth movement. The pons is also involved in dreaming sleep, in animals as well as humans, and it is thought that this might have evolved to help the animal to form the neural pathways needed for smooth movement. When we see dogs dreaming, for example, it’s evident that they are running or chasing something, which could possibly link with practising physical skills. We’ll come back to how mental rehearsal can help skill learning in Chapter 6.

The pons is connected to the cerebellum, which is the wrinkled bulge that sticks out underneath the back of the cerebrum. It’s sometimes called the mini-brain, and it is capable of carrying out many more complex functions than just keeping the animal alive. As we’ve seen, it plays an important role in skill learning. When we are first learning a new skill, our movements are often jerky and a bit clumsy, because we have to think about each movement consciously. But as we practise those movements, control of those sequences of actions moves to the cerebellum, and those movements become smooth and automatic, so we don’t have to think about doing them. The cerebellum doesn’t plan deliberate movement – that’s done by the cerebrum – but it makes sure that our actions are co-ordinated, precise and accurately timed.

Like the cerebrum, the cerebellum is organized into two halves, and its surface is folded closely like the leaves of an accordion. This suggests that the outer layers are particularly important for the cerebellum’s functioning (the grooves and folds increase the total surface area). The folds mean that its surface comprises most of its structure, but there are nerve fibres underneath them and a small space filled with fluid, known as a ventricle, at the point where it joins the pons. The cerebellum also controls balance, which is a function that appears to be located in a small knob between its two halves. Most drugs aiming to treat motion sickness have the effect of suppressing this area of the brain. In humans, the cerebellum is also included in some of the nerve pathways involved in processing attention, language and fear and pleasure reactions. So you can see that it is an important part of the brain for all complex animals.

These structures, collectively, support essential bodily processes, so we can understand why they would have evolved first.

The thalamus and the limbic system

Later on, even more complex structures began to evolve in the brain. While many simpler animals had sensory organs of some kind, reacting to light or vibrations or changes in the chemical composition of the fluid they were living in, some began to develop more sophisticated perception and evolved brain structures to deal with it. For example, there is a large area of packed cells above the midbrain and below the cerebrum known as the thalamus. It is separated into two halves, and it acts as a kind of relay station for sensory information, and for motor signals going to the muscles.

The thalamus receives information from the sensory nerves and from our eyes and ears, and does a certain amount of decoding of those signals before passing the information on to the cerebrum. It also receives the instructions about movement passed down from the cerebrum and sends those instructions on to our muscles. Like several other subcortical structures, it’s involved in sleep and wakefulness as well – those states seem to affect large areas of the brain in a general way rather than being tightly controlled by just one area.

There are a number of other small structures around the thalamus, collectively known as the limbic system. A small ‘lump’ immediately below the thalamus, known as the hypothalamus, is especially important to mammals because it regulates body temperature. It’s the ability to keep our own internal body temperature constant that allows us to be active at night or in cold places. It is also the reason why small mammals can live in underground burrows, which is a possible explanation for how they were able to survive the massive impact cataclysm that finished off the dinosaurs.

Figure 1.4 The elements of the limbic system

The hypothalamus does much more than just regulate temperature, though; it maintains homeostasis throughout the body. Maintaining homeostasis means keeping everything in a steady, comfortable condition. So if your body’s fluid levels fall below what is optimal for your survival, the hypothalamus will initiate feelings of thirst leading you to drink; if your body’s blood glucose levels fall below a certain level, it will initiate hunger, leading you to seek food. If you get too cold, it initiates shivering, which agitates your muscles to generate a little heat; and if you get too warm, it initiates sweating, so that the evaporation will cool you down. Effectively, the hypothalamus acts as the regulator to keep the body’s basic mechanisms working as they should. Its position just below the thalamus (‘hypo’ means ‘below’) allows it to have connections with all the early parts of the brain, so it can send the relevant signals when they are needed.

The hypothalamus sends its signals partly by nerve cell (neural) connections, but partly also by releasing hormones. Hormones are chemicals that either stimulate body processes or cause other hormones to be released by other glands in the body. Hormones are particularly important for maintaining ‘states’ such as growth, pregnancy, arousal or anxiety. Together, the hormone-releasing glands form the endocrine system of the body, and the hypothalamus is the brain’s main route for connecting the brain with the endocrine system.

There are many other parts of the limbic system. The hippocampus is a small curved structure underneath the cerebrum, and its name comes from the way that it was thought to resemble the shape of a seahorse. It’s important in memory in several ways. One is that it allows us to consolidate our memories into long-term memory storage. People with damage to the hippocampus, like that caused by frequently drinking alcohol without eating, can find that they become unable to store new memories. This is known as Korsakoff’s syndrome, and it can have tragic consequences.

Case study: Korsakoff’s syndrome

A case reported by the neurologist Oliver Sacks was of a 60-year-old man who had developed Korsakoff’s syndrome when he was about 30 years old. The damage to his hippocampus meant that he was unable to store any new memories: he retained only the memories from his younger self. This meant that every day when he looked in the mirror he had an unpleasant shock, not recognizing the old man he had become or remembering anything of his more recent past.

The hippocampus is concerned with other forms of memory as well – for example our spatial memory, which is how we remember where we are, and the other locations that we know. London taxi drivers, who have to memorize virtually the whole of London in order to pass the test known as ‘The Knowledge’, have shown an increase in the size of the hippocampus as a result of their increased spatial memory. So what we do in life can either damage how our brain works or improve it. It’s all about the choices we make. We’ll look at how memory works in the brain in more detail in Chapter 7.

From the evolutionary perspective, though, we can see how the ability to navigate round an area and to develop mental maps can help an animal to survive. Studies have shown, for instance, that mice allowed to explore a complex maze with no escape routes will freeze if a cat is then introduced to the area, while mice that haven’t had a chance to explore will run about looking for an escape. By exploring and remembering, the first set of mice discovers that escape isn’t possible, so staying very still to avoid attention is a better option. Incidentally, we don’t know whether the cat was allowed to catch the mice in these studies, or what happened to them in the end. In the period when they were conducted – the 1960s – little consideration was given to animal ethics, so the mice might or might not have survived. We wouldn’t do a study like that nowadays, fortunately! But it doesn’t change the main point, which is that knowing all about your location is a definite aid to survival.

Another important part of the limbic system is the amygdala. This is the emotion centre of the brain, and it consists of two almond-shaped structures located deep in the right and left temporal lobes, quite close to the hippocampus. It helps the brain to identify and react to threats, and is active in our other emotions, too – both positive and negative ones. Part of its role appears to be working with the hippocampus to consolidate memories, especially emotional ones. We are more prepared to remember things if they accompany an intense emotional experience, and this is partly the result of activity in the amygdala. We’ll come back to the actions of the amygdala in many of the chapters in this book, but particularly in Chapter 8.

Other parts of the limbic system include the basal ganglia, which is the name given to a group of cells nested deep in the white matter of the frontal lobes. These cells help us organize our movements by choosing appropriate actions, and inhibiting our actions until we know that they are suitable for the situation. The basal ganglia also include the caudate nuclei, which are also involved in planning actions and in co-ordinating the learning of habits and rule-based actions, and the area known as the globus pallidus, which is all about regulating deliberate movement so that it is co-ordinated and fluid. As you might expect, then, the basal ganglia have close links with the cerebellum, and damage to any of these areas can produce problems with movement of one kind or another.

The cingulate gyrus, or cingulate cortex, is a large area of the brain just above the corpus callosum. Although it is continuous with the cerebrum itself, it is often considered to belong to the limbic system, partly because of its connections and the way it works so closely with other parts of that system, like the hypothalamus and the amygdala. It is involved in emotions, memory and learning: among other functions, for example, it co-ordinates smells and sights with pleasant or unpleasant memories. It also seems to be involved in regulating aggressive behaviour, and it is active in the neural pathways that are stimulated by our emotional reactions to pain.

The limbic system, then, is intensely involved in emotions, memory and movement – all of which are important for animals like mammals, which need to be able to survive in a complex world. Other animals – reptiles, fish and amphibians – also possess these structures but we are not as clear about the precise roles they play. Our understanding of mammals, in terms of emotions and their learning mechanisms, is better developed, partly because it helps us to understand how our own nervous system has developed.

Remember this: Folds and grooves

Information is processed on the outer layer of the cerebrum – the cerebral cortex. In some animals, like birds or reptiles, this outer surface is relatively smooth and the cerebrum itself is not particularly large. In mammals the cerebrum is bigger, with creases and grooves, which increase its surface area. The cerebrum is the largest part of a dog or cat’s brain, and it has several deep folds. A monkey’s cerebrum is much larger than a cat’s, relative to the rest of its brain, and has many more folds and grooves. Apes have even more. By the time we reach humans, the cerebrum covers up almost all of the rest of the brain and its surface has become very convoluted indeed, with parts which can’t even be seen from the outside because they are folded right underneath. This fits neatly with our ideas about humans being more intelligent than other animals – until, that is, we look at whales and dolphins, which have even more folds and grooves in the surface of their cerebrum than humans do. Does that mean they are more intelligent than us? Nobody knows, except possibly the cetaceans, and they aren’t telling.

The cerebrum

Finally, moving upwards through the brain, or onwards through our evolutionary progression, we come to the cerebrum. This is the largest structure of all in mammals, and especially in humans (and cetaceans too, although we don’t really know what whales and dolphins do with their massive brains!). It is by far the most important part of the brain in human beings, and most of this book will be dealing with different aspects of our cerebral functioning. For now, though, it is worth taking a look at its basic structure, so that we can find our way around its different areas and sections.

Figure 1.5 The cerebral hemispheres seen from above

The cerebrum is what makes us human. It is the part of the brain that does thinking, perceiving, language, imagining and planning, decision-making, socializing, and all the other aspects of cognitive and social understanding that we use without even being aware of it. So it’s not surprising that it overshadows all the other structures. It isn’t separate from them: the surface of the cerebrum is composed of grey matter – or gray matter, if you want to spell it that way – and it consists of the cell bodies of neurones and the other cells which support them. But underneath the layer of grey matter is a compacted mass of white matter, which consists of the long fibres, or axons, connecting those neurones with other parts of the cerebrum and other parts of the brain. Our brains are full of pathways of nerve fibres, linking all the different parts together, and this book is about what neuroscientists have been able to discover about the ways these pathways work.

The cerebrum itself is divided into two halves, a bit like a giant walnut. The two halves are the left and right cerebral hemispheres. They are largely separate, but they have a crossover, a thick band known as the corpus callosum. This is a mass of nerve fibres, which passes messages from one side of the brain to the other to co-ordinate our actions and cognitions. We need this, because the two halves work together but have slightly different functions. In general, the left cerebral hemisphere controls the right side of the body while the right cerebral hemisphere controls the left side of the body. There are some other differences between them (although not as many as some people have claimed), which we’ll look at in Chapter 2.

The two cerebral hemispheres are physically very similar in structure, so the way that we name the different areas is the same for both sides of the brain. The surface, as we’ve seen, is covered by deep grooves with rounded areas between them. Each groove is known as a sulcus and the mound between the grooves is known as a gyrus. (The plurals of these are sulci and gyri, in case you come across these terms.) The deep sulcus, which divides the two halves of the cerebrum, is known as the medial sulcus. While the medial sulcus is the dividing line between the left and right cerebral hemispheres, it doesn’t separate them entirely – as we’ve seen, they are joined by the corpus callosum – but the join is so deeply buried between the two that it cannot be seen from the surface.

On each hemisphere are two particularly long and deep sulci. These divide each cerebral hemisphere into four ‘lobes’. The lateral sulcus, sometimes also called the lateral fissure, runs along the side of the brain, and the area of the brain below it is called the temporal lobe. It has many functions, as we’ll see throughout this book; and one of its distinctive ones is in processing the sounds that we hear. The other major sulcus is the central sulcus, or central fissure, which runs across the top of the brain. It separates the front part of the brain, known as the frontal lobe, from the area behind it, which is known as the parietal lobe. The frontal lobe is particularly concerned with decision-making, planning and movement, while the parietal lobe integrates various kinds of sensory information. The fourth lobe of the brain, the occipital lobe, is not defined by a sulcus as the other three are, but it is the area at the very back of the brain and it is distinctively concerned with vision.

Figure 1.6 Cortical lobes and fissures

Some of the most interesting parts of the cerebrum, though, are tucked right underneath the lobes, where they fold in on themselves. For example, under the cerebrum, but still part of it, is a thin but widespread layer of cells that links together many different areas of the cerebral cortex and connects with many of the structures in the limbic system. This is called the claustrum, which some researchers believe is crucial to consciousness and what we experience as our connected awareness. We’ll look at this again in Chapter 13. Then there is the insula, an area of the cortex folded deep inside the lateral fissure. This, too, is involved in consciousness, and also with social perceptions such as empathy, compassion, self-awareness and emotional experiences. Not only that, but the insula has strong connections with our systems for control of movement and cognition – that is, thinking and memory.

The brain, then, is a complex structure, and exploring how it works, and how its different structures connect with one another, is one of the most exciting aspects of modern science. Since neuroscientists are making new discoveries all the time, we are unable to cover them all here, but I hope this book describes enough of them for you to get an idea of what is where, and how your brain makes you into the person you are.

Focus points

✽  The brain began as an extension of a simple tube linking a primitive nervous system. It became increasingly complex as animals evolved.

✽  The parts of the brain closest to the spinal cord deal with essential life-maintaining processes, like breathing, heartbeat, digestion and alertness.

✽  Larger subcortical structures include the thalamus and the cerebellum. The thalamus co-ordinates sensory information while the cerebellum co-ordinates movement.

✽  The limbic system is a collection of small structures that includes the amygdala, the hippocampus and the basal ganglia, which are important in emotions, memory and learning.

✽  The largest part of the human brain is the cerebrum, which is divided into two halves that cover almost all of the rest of the brain, and are wrinkled and folded to increase their surface area.

Next step

In the next chapter, we’ll look more closely at how the different parts of the brain work and what brain studies and brain scanning reveal.