Indholdsfortegnelse for How It Works: Inside Your Brain i How It Works: Inside Your Brain

It’s no secret that the human brain is a marvellous thing. From the movements you rely on every day to the emotions you express, the dreams that feel real and the thoughts that whizz through your mind, the brain controls it all. Centuries of study have yielded many answers to its countless mysteries. We know about the synapses and neurons that make up the brain, and leading surgeons can now map someone’s brain and perform once impossible operations. But there is still so much that we don’t understand. What does it really mean to be conscious? Why do we have cognitive biases when the facts contradict us? And why are some people psychopaths who see the world in a totally different way? In this book you’ll explore some of the…

It’s a computer, a thinking machine, a fatty pink organ, and a vast collection of neurons – but how does it actually work? The human brain is amazingly complex – in fact, more complex than anything in the known universe. The brain effortlessly consumes power, stores memories, processes thoughts and reacts to danger. In some ways, the human brain is like a car engine. The fuel – which could be the sandwich you had for lunch or a sugar doughnut for breakfast – causes neurons to fire in a logical sequence and to bond with other neurons. This combination of neurons occurs incredibly fast, but the chain reaction might help you compose a symphony or recall entire passages of a book, help you pedal a bike or write an email…

Your brain is arguably your most important organ, and it is vital that it isn’t affected by wayward chemicals or aggressive infections. To keep your nerve cells safe, your body builds a biological wall called the blood-brain barrier. Blood vessels are the highway of the human body, carrying nutrients and oxygen to tissues and taking away waste products, but unfortunately they can also transport harmful chemicals and infections. In most parts of the body, chemicals are able to freely cross through the walls of the blood vessels, leaking between the cells and out into the tissues, but thankfully this does not occur in the brain. To prevent unwanted contaminants from entering, the cells lining the blood vessels are closely knitted together by structures called ‘tight junctions’. Web-like strands pin the…

How are you feeling right now? Are you relaxed laying on your sofa and listening to the gentle sounds of the dawn chorus outside your window? Or maybe you are tense with your shoulders hunched up around yourself as you try to get five minutes peace in a busy office? You would think that it is easy to work out if we are happy or sad, angry or calm, but humans cycle through such a vast array of emotions throughout their lives it can be difficult to distinguish them from one another. Emotions are not a simple experience. Every time you feel something your body initiates a physiological change, a chemical release and a behavioural response. This process involves multiple processes working together, including your major organs, neurotransmitters and limbic system.…

As light reflects off objects, waves enter the eye through the pupil. They’re refracted by the lens and the cornea so that they reach the retina at the back of the eye. The retina is a sensory membrane made up of millions of light-sensitive nerve cells that fire electrical signals along the optic nerve to the brain when they’re stimulated by light waves. Because light travels in straight lines and enters the eye through a small, curved aperture, waves reflecting off objects above the eye hit the bottom of the retina and vice versa. This creates an inverted image of the world, but the brain processes these signals to produce a final image that matches the true orientation of the landscape. As members of a predator species, our eyes are…

Scientists aim to measure consciousness using specialist equipment like brain scanners. These record a person’s brain activity while they are thinking about different things or receiving different stimuli. Scientists can then analyse this activity to look for patterns that can explain certain behaviours. Most neuroscientists agree that consciousness involves combining information from different parts of the brain. There is growing evidence to suggest that an area called the claustrum is where this information is combined. Neurons in the claustrum connect to most other brain areas, especially the cortex. The cortex is the outer part of the mammalian brain and is responsible for lots of tasks, such as receiving and interpreting sensory information (i.e. sound and vision). The claustrum could link all these processing areas and combine their products to produce…

At the end of a long day, there’s nothing as inviting as a cosy bed. After little sleep the night before, a day packed with activity or hours of solid concentration, it can become a challenge just to keep your eyes open. Most people are lucky enough to sleep comfortably and safely, but becoming unconscious and paralysed put our ancestors at risk of attack from enemies and animals. The benefits must have outweighed the dangers, but why did humans evolve to spend so much of their lives asleep in the first place? The real answer is that no one’s completely sure. While we’ve moved on from Lucretius’ theory of ominous air particles attacking the spirit each night, many of the exact details about our time spent slumbering remain a mystery.…

There is still so much we don’t know about the human brain. However, if something goes wrong and it needs an operation, you will find yourself in need of a neurosurgeon. These guys can operate on the vast number of structures within the brain and spinal cord and have a full arsenal of techniques and – literally – cutting-edge technologies to hand. A neurosurgeon’s workload comes in two main forms. The emergency work is often a result of road traffic accidents or fights and often affects young men with head injuries. These patients may have bleeding within the skull, which is exerting pressure on the brain – the neurosurgeon must relieve that pressure. There is also the planned work, where neurosurgeons try to remove tumours without causing any damage to…

As you go about your daily life, your brain continuously perceives the world around you with the help of your senses. The constant stream of information it receives is overwhelming, so it regularly takes shortcuts to simplify what you see or feel and chooses the most likely interpretations. This helps it to concentrate on what’s important, rather than focusing on everything at once. The brain is also very good at predicting the future, helping it to compensate for the slight delay between you physically seeing or touching something and receiving and processing those signals from your eyes or limbs. However, these shortcuts and predictions also make it possible for your brain to be fooled. Humans have been discovering ways to trick the mind for millennia, with examples of optical illusions…

Sugar pills ease depression, colourful creams numb the skin and saline injections make pain melt away. The placebo effect is a powerful healer, but how does it actually work? In the 1890s, Ivan Pavlov discovered classical conditioning. His famous experiments taught dogs to associate the sound of a bell with the arrival of food. When they heard the noise, they started to dribble in anticipation. The same thing can happen to us with medicine. We make associations based on our experiences. If people take aspirin for a headache, they start to associate the shape and taste of the tablets with pain relief. Replace the pills with a placebo and the pain will still be lessened. Placebos, also known as ‘dummy’ or ‘inactive’ treatments, are made from inert substances like saline,…

“Our brains take shortcuts to enable rapid judgements – known as heuristics – whereby we prioritise certain parts of larger problems” As humans living in an ever-changing world, we have rather a lot to think about. We make hundreds of decisions everyday, from simple choices like what to eat for breakfast to devising complex business strategies at work. As we are bombarded by sensory inputs, each providing new information to process, we must draw on previous experiences to recognise, understand and act on our perception of the world. To do this our brains take shortcuts to enable rapid judgements – known as heuristics – whereby we prioritise certain parts of larger problems over others. While this is a critical coping mechanism to compensate for the limited processing amplitude of the…

Memory recall is a critical brain function, yet we experience so much sensory input that we rely on mental shortcuts to identify familiar stimuli. The availability heuristic, first described by Amos Tversky and Daniel Kahneman, is the process of unconsciously prioritising most recently acquired information, biasing assessments of a situation on that which is most easily recalled. Research has shown how participants overestimate the relevance of information that they are able to easily remember, even if this is a first impression of the broader situation. The likely thought process is that we assume if information is readily available to recall it must be more important than that which does not quickly come to mind. While cognitively useful, the implications for judicial decisions, education-curriculum design and learning performance are significant, where…

The brain makes up just two per cent of our total body weight, but crammed inside are approximately 86 billion neurons, surrounded by 180,000 kilometres of insulated fibres connected at 100 trillion synapses. It’s a vast biological supercomputer. The cells in the brain communicate using electrical signals. When a message is sent, thousands of microscopic channels open, allowing positively charged ions to flood across the membrane. Afterwards, more than 1 million miniature pumps in each cell move the ions back again ready for the next impulse. The cell bodies of the neurons, and their connections, are contained within the grey matter, which consumes 94 per cent of the oxygen delivered to the brain. Different areas are responsible for different functions, and wiring them together is a fatty network of fibres…

It’s true that the different sides of the brain perform different tasks, but do these anatomical asymmetries really define our personalities? Some psychologists argue that creative, artistic individuals have a more developed right hemisphere, while analytical, logical people rely more heavily on the left side of the brain, but so far the evidence for this two-sided split has been lacking. A team at the University of Utah attempted to answer the question by dividing the brain up into 7,000 regions and analysing the fMRI scans of over 1,000 people in order to determine whether the networks on one side of the brain were stronger than the networks on the other. Despite the popularity of the left versus right brain myth, the team (who published their findings in the journal PLOS…

The pea-sized pituitary gland is found at the base of the brain, close to the hypothalamus. At a glance, it looks a relatively insignificant part of the brain, but it actually plays a role in many vital systems. Often referred to as the ‘master gland’, it not only releases hormones that control various functions, but it also prompts the activity of other glands like the ovaries and testes. The pituitary gland comprises three sections called lobes: the anterior, the posterior and the intermediate – the latter of which is considered part of the anterior lobe in humans. These work together with the hypothalamus, which monitors hormones in the blood and stimulates the pituitary gland to produce/release the appropriate hormone(s) if levels fall too low. The anterior lobe produces seven important…

Memory is the capacity to store and retain information, then recall it for use when needed. It is used by most organisms to operate in the most successful manner they possibly can in their unique environment. There are three main types of memory: sensory, short-term and long-term, although long-term is often split into different types of memory. Sensory memory is a very short-term type of memory that is evoked through the senses. It lasts for a few seconds at most and is not stored. Short-term memory is a slightly longer-lasting form – around 20 seconds. It’s the recording of memories currently being used – i.e. remembering a number to dial in the next 30 seconds. If the information is repeated, however, it causes pathways to form between neurons in the…

Humans are highly social animals, relying on others for comfort, safety and happiness. We live in large groups and often have additional connections outside of our close circles, and we’re able to do this in part because we possess the ability to remember and identify faces. Faces of those who are important to us – whether for positive or negative reasons – are stored in our brains ready for the next time we encounter them. Even after years apart, old friends can recognise each other across the street, while the face of a stranger walking past fades from the memory almost instantly. A part of the brain called the fusiform gyrus is often closely associated with face and body recognition. It forms part of the ventral temporal cortex, which is…

The fight or flight response is all-consuming. Your heart beats faster, your breathing becomes quick and deep, your palms sweat, and your mouth goes dry. With fractions of seconds to react in the face of danger, this is what gets you out of harm’s way before you’ve even had time to think. It’s an ancient self-defence mechanism that’s hardwired into the nervous system – your body’s way of getting you ready for battle. The body’s panic button is a walnut-sized piece of brain tissue called the amygdala, and its job is to monitor incoming sensory signals for signs of threat. It is connected to a larger brain area called the thalamus, which acts as the brain’s sensory relay. The thalamus gathers inputs from the brain’s sensory processing areas and from…

Numerous mental health conditions are based on conscious and subconscious thoughts. For example, people with obsessive-compulsive disorder (OCD) – a broad condition involving repetitive behaviours and routines – may experience intrusive thoughts. These are negative or inappropriate thoughts that occupy their conscious mind. Thoughts like ‘Have I locked the front door?’ or ‘Did I leave the stove on?’ can overcome the person, meaning they are unable to think of anything else in that moment. Post-traumatic stress disorder (PTSD) and personality disorders can arise from people forcing certain distressing thoughts out of their consciousness. This results in unhealthy coping behaviours and leads to unpleasant experiences such as flash-backs, where the upsetting thoughts and images suddenly enter the person’s consciousness. Having a greater understanding of what conscious thoughts are and how they…

Brains are complex, as is music, so teasing out the neurological response to melodies is something of a challenge, but researchers across the world have been working to demystify the baffling science behind it. The first components of music to be processed by the brain are the basic sounds – pitch, length and volume. From this, the brain then teases out melody and distinguishes between different instruments. This information is then compared to memories, establishing whether the incoming sound is familiar and revealing any linked emotions. All together, the processing leads to a response, whether that’s switching the song off or starting to dance. And if you move, that feeds back into your brain again, affecting the experience even further. Some of the complexities of the brain’s response to music…

As the father of modern-day neurological surgery, Harvey Cushing pioneered the medical profession, inspiring future generations to reap the rewards of his insightful studies and profound discoveries. Born in Cleveland, Ohio, in 1869, he was the next generation in a long line of physicians, following his father, grandfather and great-grandfather. Inheriting a thirst for knowledge and aptitude for science, Cushing graduated from the prestigious Yale University in 1891. His first venture in the world of medicine began while studying at Harvard Medical School, completing his degree four years later. To this day seen as the hub for surgical excellence, Cushing moved to Baltimore to train at Johns Hopkins Hospital as a surgeon. Under the watchful eye of William S Halsted, a surgical pioneer in his own right, he flourished, taking…

When you look at two objects next to each other, you are probably pretty confident in identifying whether they are the same size or if one is bigger than the other. However, there are certain optical illusions that prove you might not always get it right. That is because our brains often make judgements about the size of an object based on other objects that are nearby, and so can easily be fooled by context. Take, for example, the Ebbinghaus illusion on the top right of this page. Many would consider the orange circle on the right to be larger than the one on the left, but they are in fact both exactly the same size. The brain uses the blue circles to judge the orange circles’ size, and so…

It can be a challenge to consider information that is not observable in our assessment of a situation. Where a person or object is not present, humans will naturally focus on those that we can see and form an opinion based solely on that condition. Survivorship bias refers to situations where we make assumptions based on the apparent success of a group of objects or people but fail to recognise that our sample is not representative of subjects that have been excluded. Looking at data of injuries sustained by car crash survivors, we may conclude that the worst injuries occur when sitting in the front seats, when in fact this data does not include people who were sat in rear seats and were killed in the accidents. To say better…

During the Neolithic period, our ancient ancestors practised a primitive form of brain surgery known as trepanning, possibly practising their skills on cows. The ancient Egyptians thought that the heart, not the brain, was the source of human emotions and intelligence, but they came to recognise that injury or damage to one side of the brain could paralyse limbs on the opposite side of the body, as illustrated in the Edwin Smith papyrus, one of the oldest medical texts in the world. Neuroscience was born roughly 2,500 years ago when Greek physician Hippocrates began to study the brain, an undertaking that led him to deduce that the brain was responsible for emotion, thought, sensations and cognition. The father of medicine was later followed by the leading physician in the Roman…

Your brain is an incredible thing. It is one of the most complex structures in the known universe, and for decades, scientists have been teasing it apart to find out what it’s made of and how it works. The brain is an electrical and chemical circuit, and nerve cells, or neurons, are the components. They each have a cell body, which contains their genetic code, an axon to transmit electrical impulses and dendrites to receive them. They are connected together at junctions known as synapses. When an impulse arrives, packets of molecules are released, passing the message on. Each neuron makes thousands of connections, producing the complicated patterns that drive human thought. There are hundreds of different types of neuron in the brain, categorised according to their unique structure and…

Sleep is one of the brain’s great mysteries, but research has revealed an intriguing night-time cleanup system. The brain is shielded by a barrier made and maintained by cells called astrocytes. They hug the blood vessels, controlling what’s allowed in and out, and a space between the vessel wall and these cells seems to play a crucial role in keeping the brain clean. At night, the astrocytes relax their grip and the space fills up with a clear liquid called cerebrospinal fluid (CSF). It’s pushed along by the movement of the blood vessels underneath, swishing up through the astrocytes and out into the spaces between brain cells. As it passes, it picks up waste and debris, carrying the particles back towards the bloodstream so they can be removed from the…

Can you imagine a purple dragon riding a bicycle with three wheels? No other animal on the planet has that power. You have the ability to take mental images of objects you’ve seen before, break them down into their component parts and rebuild them into something new. Combine a reptile and a bird and you have your dragon. Recall the purple colour of a flower and you can paint its skin. Think about the mechanics of riding a bicycle and you’ll be able to position its body on the frame, forelegs on the handlebars, hindlegs on the pedals. Now you just need to decide where you want to put that third wheel. This skill is incredible, and it’s shaped the course of human history. Culture, engineering, art, science, music, technology:…

The brain is a powerful learning machine; it has the ability to learn from previous experiences in order to ‘predict’ future events. This is known as anticipatory timing and it is what enables humans to successfully navigate the world that we live in and also plays a key role in helping us to concentrate. But how does the brain do this? Researchers think two different regions are responsible for its ability to ‘predict’ the future. These regions are known as the basal ganglia, a group of structures that are found deep within the cerebral hemisphere, and the cerebellum, which is located at the back of the brain. Both structures are associated with cognition and movement. The basal ganglia is associated with tasks that involve rhythm – such as singing along…

To demonstrate just how complex a subject consciousness is, let’s explore the vast range of definitions provided by authority figures. The Oxford English Dictionary gives not one but three definitions of consciousness: ‘The state of being aware of and responsive to one’s surroundings’, ‘a person’s awareness or perception of something’, and ‘the fact of awareness by the mind of itself and the world’. The English philosopher John Locke said, “Consciousness is the perception of what passes in a man’s own mind.” Dr Giulio Tononi, a neuroscientist, psychiatrist, and leading authority on the brain during sleep, defines consciousness as that which “corresponds to the capacity of a system to integrate information”. The famous philosopher Descartes stated, “I think therefore I am.” And the psychologist and philosopher William Davidson needed six pages…

The human brain is one of the most complex structures in the known universe and understanding how it works is an enormous scientific undertaking. Modern neuroscience brings together experts from a huge array of fields, and by using a combination of the most advanced technologies, medical techniques, biological research and computational modelling, scientists are finally beginning to untangle the many profound mysteries of the brain. Building a brain Large-scale projects aim to simulate the human brain at every level How mind control works Simple equipment and complex computer programming allow our thoughts to be transmitted over the internet Mind control In a groundbreaking experiment in 2013, researchers at the University of Washington successfully linked two human brains together and proved their principle with a video game. A city is under…

Scientists are exploiting ways to connect the human brain to modern prostheses (such as artificial limbs) or via computers to expand our functionality. It’s hoped patients will be the ones to benefit, particularly those who have lost limbs. Motor prostheses interpret the natural signals sent from the brain. The electrical signals sent are detected using microelectrodes, which can be implanted underneath the skin or even buried into nerves. The brain signals for each particular movement are unique and slightly different, and the aim is to detect these individually to allow patients the ability to perform fine movements. However, the science is still developing to more accurately recognise these signals, and the perfect prosthesis does not yet exist. The initial technology was developed with monkeys and has come a long way…

Rubber hand illusion Trick your mind into believing that a fake hand is your own 1 Hide your hand Place an open book on the table in front of you, then sit with one hand underneath the book so that you cannot see it. Put the rubber hand in front of you so that it is lined up with your shoulder. Covering your arm and the ‘arm’ of the fake hand with a cloth will help the illusion. 2 Start stroking Get a friend to stroke the middle finger of your real hand and the middle finger of the fake hand at the same time. After one or two minutes you will start to feel like the fake hand is your own and that your real hand no longer exists.…

Sport and gambling are two activities that are most obviously affected by cognitive biases and are two of the most studied. This is largely due to the great influence individual perception can have on our ability to see patterns in events and predict future outcomes. The clustering illusion bias is centred around the human predisposition to see events closely distributed in time as related, when in fact such events are random. The most famous example of a study of this effect is a 1985 investigation carried out by psychologists Gilovich, Vallone and Tversky, of Cornell and Stanford Universities, on the ‘Hot Hand Fallacy’ – the belief that in basketball a player is more likely to score if previous attempts have been successful. While confidence can improve performance, this incorrect assumption…

The brain is divided into three main parts: the cerebrum, cerebellum and the brain stem. The largest is the cerebrum, which consists of four lobes: the frontal, parietal, occipital and temporal lobes. Each region is associated with different functions, and they work together to control our bodies. The brain has an estimated 86 billion nerve cells, or neurons, through which information is constantly transmitted to different parts of our body, allowing us to make sense and respond to the world around us. Between different neurons are trillions of miniscule gaps called synapses, where signals are passed from one brain cell to the next. Given that the brain is such a highly complex and specialised organ, when it is injured or damaged the results can be devastating. In England alone it’s…

As the control centre for our entire bodies, the brain dictates every aspect of the physical being and our mental ability. From the simple act of moving a limb to complex thought and defining our personalities, millions of electrical–conducting neurons act as microscopic messengers, sending instructions around the body. But what if science was able to hijack those messages and start sending a few of its own? Theoretically, by redirecting some of the electrical signals and sending them through pieces of technology, scientists are able to use brain power to control machines. This technique of hacking the brain has been realised with the creation of the brain-computer interface (BCI). Typically split into three categories, BCIs facilitate the communication between the brain and a machine. The first method of creating a…