About This Book

This introductory section ends with a primer on basic brain anatomy, techniques, and terminology. Chapter 1 then kicks off the myth-busting by providing some historical context, including showing how our understanding of the brain has evolved since Ancient times, and detailing outdated myths that are no longer widely believed, but which linger in our proverbs and sayings. This includes the centuries' long belief that the mind and emotions are located in the heart – an idea betrayed through contemporary phrases like “heart break” and “learn by heart.” Chapter 2 continues the historical theme, looking at brain techniques that have entered psychiatric or neurological folklore, such as the brutal frontal lobotomy. Chapter 3 examines the lives and brains of some of neurosciences mythical figures – including the nineteenth century rail worker Phineas Gage, who survived an iron rod passing straight through his brain, and Henry Molaison, the amnesiac who was examined by an estimated 100 psychologists and neuroscientists.

Chapter 4 moves on to the classic brain myths that refuse to die away. Many of these will likely be familiar to you – in fact, maybe you thought they were true. This includes the idea that right-brained people are more creative; that we use just 10 percent of our brains; that women lose their minds when they are pregnant; and that neuroscience is changing human self-understanding. We'll see that there is a grain of truth to many of these myths, but that the reality is more nuanced, and often more fascinating, than the myths suggest.

Chapter 5 deals with myths about the physical structure of the brain, including the idea that bigger means better. And we'll look at mythology surrounding certain types of brain cells – the suggestion that mirror neurons are what makes us human and that you have in your brain a cell that responds only to the thought of your grandmother.

Next we turn to technology-related myths about the brain. These relate to the kind of topical claims that make frequent appearances in the press, including the ubiquitous suggestion that brain scans can now read your mind, that the Internet is making us stupid, and that computerized brain training games are making you smart.

The penultimate chapter deals with the way the brain relates to the world and the body. We'll debunk the popular misconception that there are only five senses, and we'll also challenge the idea that we really see the world exactly how it is.

The book concludes in Chapter 8 by dealing with the many misconceptions that exist about brain injury and neurological illness. We'll see how conditions like epilepsy and amnesia are presented in Hollywood films and tackle the widespread belief that mood disorders somehow arise from a chemical imbalance in the brain.

The Need for Humility

To debunk misconceptions about the brain and present the truth about how the brain really works, I've pored over hundreds of journal articles, consulted the latest reference books and in some cases made direct contact with the world's leading experts. I have strived to be as objective as possible, to review the evidence without a pre-existing agenda.

However, anyone who spends time researching brain myths soon discovers that many of today's myths were yesterday's facts. I am presenting you with an account based on the latest contemporary evidence, but I do so with humility, aware that the facts may change and that people make mistakes. While the scientific consensus may evolve, what is timeless is to have a skeptical, open-minded approach, to judge claims on the balance of evidence, and to seek out the truth for its own sake, not in the service of some other agenda. I've written the book in this spirit and in the accompanying box on p. 7 I present you with six tips for applying this skeptical, empirical approach, to help you spot brain myths for yourself.

Before finishing this Introduction with a primer on basic brain anatomy, I'd like to share with you a contemporary example of the need for caution and humility in the field of brain mythology. Often myths arise because a single claim or research finding has particular intuitive appeal. The claim makes sense, it supports a popular argument, and soon it is cemented as taken-for-granted fact even though its evidence base is weak. This is exactly what happened in recent years with the popular idea, accepted and spread by many leading neuroscientists, that colorful images from brain scans are unusually persuasive and beguiling. Yet new evidence suggests this is a modern brain myth. Two researchers in this area, Martha Farah and Cayce Hook, call this irony the “seductive allure of ‘seductive allure.'”⁵

Brain scan images have been described as seductive since at least the 1990s and today virtually every cultural commentary on neuroscience mentions the idea that they paralyze our usual powers of rational scrutiny. Consider an otherwise brilliant essay that psychologist Gary Marcus wrote for the New Yorker late in 2012 about the rise of neuroimaging: “Fancy color pictures of brains in action became a fixture in media accounts of the human mind and lulled people into a false sense of comprehension,” he said (emphasis added).⁶ Earlier in the year, Steven Poole writing for the New Statesman put it this way: “the [fMRI] pictures, like religious icons, inspire uncritical devotion.”⁷

What's the evidence for the seductive power of brain images? It mostly hinges on two key studies. In 2008, David McCabe and Alan Castel showed that undergraduate participants found the conclusions of a study (watching TV boosts maths ability) more convincing when accompanied by an fMRI brain scan image than by a bar chart or an EEG scan.⁸ The same year, Deena Weisberg and her colleagues published evidence that naïve adults and neuroscience students found bad psychological explanations more satisfying when they contained gratuitous neuroscience information (their paper was titled “The Seductive Allure of Neuroscience Explanations”).⁹

What's the evidence against the seductive power of brain images? First off, Farah and Hook criticize the 2008 McCabe study. McCabe's group claimed that the different image types were “informationally equivalent,” but Farah and Hook point out this isn't true – the fMRI brain scan images are unique in providing the specific shape and location of activation in the temporal lobe, which was relevant information for judging the study. Next came a study published in 2012 by David Gruber and Jacob Dickerson, who found that the presence of brain images did not affect students' ratings of the credibility of science news stories.¹⁰

Was this failure to replicate the seductive allure of brain scans an anomaly? Far from it. Through 2013 no fewer than three further investigations found the same or a similar null result. This included a paper by Hook and Farah themselves,¹¹ involving 988 participants across three experiments; and another led by Robert Michael involving 10 separate replication attempts and nearly 2000 participants. Overall, Michael's team found that the presence of a brain scan had only a tiny effect on people's belief in an accompanying story.¹² The result shows “the ‘amazingly persistent meme of the overly influential image' has been wildly overstated,” they concluded.

So why have so many of us been seduced by the idea that brain scan images are powerfully seductive? Farah and Hook say the idea supports non-scanning psychologists' anxieties about brain scan research stealing all the funding. Perhaps above all, it just seems so plausible. Brain scan images really are rather pretty, and the story that they have a powerful persuasive effect is very believable. Believable, but quite possibly wrong. Brain scans may be beautiful but the latest evidence suggests they aren't as beguiling as we once assumed. It's a reminder that in being skeptical about neuroscience we must be careful not to create new brain myths of our own.

A Primer on Basic Brain Anatomy, Techniques, and Terminology

Hold a human brain in your hands and the first thing you notice is its impressive heaviness. Weighing about three pounds, the brain feels dense. You also see immediately that there is a distinct groove – the longitudinal fissure – running front to back and dividing the brain into two halves known as hemispheres (see Plate 1). Deep within the brain, the two hemispheres are joined by the corpus callosum, a thick bundle of connective fibers (see Plate 2). The spongy, visible outer layer of the hemispheres – the cerebral cortex (meaning literally rind or bark) – has a crinkled appearance: a swathe of swirling hills and valleys, referred to anatomically as gyri and sulci, respectively.

The cortex is divided into five distinct lobes: the frontal lobe, the parietal lobe near the crown of the head, the two temporal lobes at each side near the ears, and the occipital lobe at the rear (see Plate 1). Each lobe is associated with particular domains of mental function. For instance, the frontal lobe is known to be important for self-control and movement; the parietal lobe for processing touch and controlling attention; and the occipital lobe is involved in early visual processing. The extent to which mental functions are localized to specific brain regions has been a matter of debate throughout neurological history and continues to this day (see pp. 40, 45, and 80).

Hanging off the back of the brain is the cauliflower-like cerebellum, which almost looks like another mini-brain (in fact cerebellum means “little brain”). It too is made up of two distinct hemispheres, and remarkably it contains around half of the neurons in the central nervous system despite constituting just 10 percent of the brain's volume. Traditionally the cerebellum was associated only with learning and motor control (i.e. control of the body's movements), but today it is known to be involved in many functions, including emotion, language, pain, and memory.

Holding the brain aloft to study its underside, you see the brain stem sprouting downwards, which would normally be connected to the spinal cord. The brain stem also projects upwards into the interior of the brain to a point approximately level with the eyes. Containing distinct regions such as the medulla and pons, the brain stem is associated with basic life support functions, including control of breathing and heart rate. Reflexes like sneezing and vomiting are also controlled here. Some commentators refer to the brain stem as “the lizard brain” but this is a misnomer (see p. 137).

Slice the brain into two to study the inner anatomy and you discover that there are a series of fluid-filled hollows, known as ventricles (see p. 22 and Plate 7), which act as a shock-absorption system. You can also see the midbrain that sits atop the brainstem and plays a part in functions such as eye movements. Above and anterior to the midbrain is the thalamus – a vital relay station that receives connections from, and connects to, many other brain areas. Underneath the thalamus is the hypothalamus and pituitary gland, which are involved in the release of hormones and the regulation of basic needs such as hunger and sexual desire.

Also buried deep in the brain and connected to the thalamus are the horn-like basal ganglia, which are involved in learning, emotions, and the control of movement. Nearby we also find, one on each side of the brain, the hippocampi (singular hippocampus) – the Greek name for “sea-horse” for that is what early anatomists believed it resembled. Here too are the almond-shaped amygdala, again one on each side. The hippocampus plays a vital role in memory (see p. 46) and the amygdala is important for memory and learning, especially when emotions are involved. The collective name for the hippocampus, amygdala, and related parts of the cortex is the limbic system, which is an important functional network for the emotions (see Plate 3).

The brain's awesome complexity is largely invisible to the naked eye. Within its spongy bulk are approximately 85 billion neurons forming a staggering 100 trillion plus connections (see Plate 4). There are also a similar number of glial cells (see Plate 5), which recent research suggests are more than housekeepers, as used to be believed, but also involved in information processing (see p. 149). However, we should be careful not to get too reverential about the brain's construction – it's not a perfect design by any means (more about this on p. 135).

In the cortex, neurons are arranged into layers, each containing different types and density of neuron. The popular term for brains – “gray matter” – comes from the anatomical name for tissue that is mostly made up of neuronal cell bodies. The cerebral cortex is entirely made up of gray matter, although it looks more pinkish than gray, at least when fresh. This is in contrast to “white matter” – found in abundance beneath the cortex – which is tissue made up mostly of fat-covered neuronal axons (axons are a tendril-like part of the neuron that is important for communicating with other neurons, see Plate 6). It is the fat-covered axons that give rise to the whitish appearance of white matter.

Neurons communicate with each other across small gaps called synapses. This is where a chemical messenger (a “neurotransmitter”) is released at the end of the axon of one neuron, and then absorbed into the dendrite (a branch-like structure) of a receiving neuron (see Plate 6). Neurons release neurotransmitters in this way when they are sufficiently excited by other neurons. Enough excitation causes an “action potential,” which is when a spike of electrical activity passes the length of the neuron, eventually leading it to release neurotransmitters. In turn these neurotransmitters can excite or inhibit receiving neurons. They can also cause slower, longer-lasting changes, for example by altering gene function in the receiving neuron.

Traditionally, insight into the function of different neural areas was derived from research on brain-damaged patients. Significant advances were made in this way in the nineteenth century, such as the observation that, in most people, language function is dominated by the left hemisphere (see p. 41). Some patients, such as the railway worker Phineas Gage, have had a particularly influential effect on the field (see p. 37). The study of particular associations of impairment and brain damage also remains an important line of brain research to this day. A major difference between modern and historic research of this kind is that today we can use medical scanning to identify where the brain has been damaged. Before such technology was available, researchers had to wait until a person had died to perform an autopsy.

Modern brain imaging methods are used not only to examine the structure of the brain, but also to watch how it functions. It is in our understanding of brain function that the most exciting findings and controversies are emerging in modern neuroscience (see p. 177). Today the method used most widely in research of this kind, involving patients and healthy people, is called functional magnetic resonance imaging (fMRI; see Plate 8). The technique exploits the fact that blood is more oxygenated in highly active parts of the brain. By comparing changes to the oxygenation of the blood throughout the brain, fMRI can be used to visualize which brain areas are working harder than others. Furthermore, by carefully monitoring such changes while participants perform controlled tasks in the brain scanner, fMRI can help build a map of what parts of the brain are involved in different mental functions. Other forms of brain scanning include Positron Emission Tomography (PET) and Single-Photon Computed Tomography, both of which involve injecting the patient or research participant with a radioactive isotope. Yet another form of imaging called Diffusion Tensor Imaging (DTI) is based on the passage of water molecules through neural tissue and is used to map the brain's connective pathways. DTI produces beautifully complex, colorful wiring diagrams (see Plate 13). The Human Connectome Project, launched in 2009, aims to map all 600 trillion wires in the human brain.

An older brain imaging technique, first used with humans in the 1920s, is electroencephalography (EEG), which involves monitoring waves of electrical activity via electrodes placed on the scalp (see Plate 23). The technique is still used widely in hospitals and research labs today. The spatial resolution is poor compared with more modern methods such as fMRI, but an advantage is that fluctuations in activity can be detected at the level of milliseconds (versus seconds for fMRI). A more recently developed technique that shares the high temporal resolution of EEG is known as magnetoencephalography, but it too suffers from a lack of spatial resolution.

Brain imaging is not the only way that contemporary researchers investigate the human brain. Another approach that's increased hugely in popularity in recent years is known as transcranial magnetic stimulation (TMS). It involves placing a magnetic coil over a region of the head, which has the effect of temporarily disrupting neural activity in brain areas beneath that spot. This method can be used to create what's called a “virtual lesion” in the brain. This way, researchers can temporarily knock out functioning in a specific brain area and then look to see what effect this has on mental functioning. Whereas fMRI shows where brain activity correlates with mental function, TMS has the advantage of being able to show whether activity in a particular area is necessary for that mental functioning to occur.

The techniques I've mentioned so far can all be used in humans and animals. There is also a great deal of brain research that is only (or most often) conducted in animals. This research involves techniques that are usually deemed too invasive for humans. For example, a significant amount of research with monkeys and other nonhuman primates involves inserting electrodes into the brain and recording the activity directly from specific neurons (called single-cell recording). Only rarely is this approach used with humans, for example, during neurosurgery for severe epilepsy. The direct insertion of electrodes and cannulas into animal brains can also be used to monitor and alter levels of brain chemicals at highly localized sites. Another ground-breaking technique that's currently used in animal research is known as optogenetics. Named 2010 “method of the year” by the journal Nature Methods, optogenetics involves inserting light-sensitive genes into neurons. These individual neurons can then be switched on and off by exposing them to different colors of light.

New methods for investigating the brain are being developed all the time, and innovations in the field will accelerate in the next few years thanks to the launch of the US BRAIN Initiative and the EU Human Brain Project. As I was putting the finishing touches to this book, the White House announced a proposal to double its investment in the BRAIN Initiative “from about $100 million in FY [financial year] 2014 to approximately $200 million in FY 2015.”