Innholdsfortegnelse for EG07 i New Scientist - The Essential Guides

Intriguingly, one type of rare, oversized neuron seems to be particularly involved in emotions and empathy, and some scientists believe it may play an important role in human consciousness. These neurons are called spindle cells, or von Economo neurons (VENs) after Constantin Freiherr von Economo, the Austrian anatomist who first spotted them. They are big – at least 50 per cent, and sometimes up to 200 per cent, larger than typical human neurons. While most neurons have a pyramid-shaped body with a finely branched tree of connections called dendrites at each end of the cell, VENs have a longer, spindly cell body with a single projection at each end with very few branches. These neurons are rare, making up just 1 per cent of the neurons in the two small…

THE brain starts to take shape within four weeks of conception, when one of three layers of cells in the embryo rolls up to form what is known as the neural tube. A week later, the top of this tube bends over, creating the basic structure of forebrain, midbrain and hindbrain. In the first two trimesters of pregnancy, development is all about putting the basic building blocks in place: growing neurons and connections and making sure each section of the brain grows properly and in the right area. ← Turn back to page 6 to recap the basic structures of the brain and their functions This process is largely controlled by genes, but it takes a huge amount of energy and a variety of nutrients in the right quantities at…

MEN are good at map-reading; women can’t park cars. Men are better at fixing stuff – but only one thing at a time. Women, by contrast, can multitask, and do empathy and intuition better, too. Just don’t ask them to think logically in a crisis. So say the stereotypes, anyway. It is a widespread idea that men and women are distinguished not only by their genitals and related sexual characteristics, but also by their brains. Take the notorious Google internal memo from 2017, in which employee James Damore asserted that there were more men in the company’s workforce because women’s high level of empathy and lower interest in coding made them less suited to Google-type work. According to this way of thinking, the biological blueprint that determines fixed and inevitable…

At first, the answer seems obvious: memory is about the past. It is your personal database of things you have experienced. In fact, this repository has a purpose that goes way beyond merely recalling old information – it helps us work out how to use it. Some of the best evidence of this comes from studies of people with brain damage or amnesia. One iconic case was of a patient known as KC in the early 1980s. After a motorcycle accident, he was left with an impaired episodic memory: he could remember facts, but not personal experiences. The weird thing was, it also stopped him imagining the future. We now know there is a strong link between being able to remember past events and being able to plan for the…

Don’t panic, but our brains have been getting smaller for at least 10,000 years. An average European woman today, for example, has a brain about 15 per cent smaller than that of her counterpart at the end of the last ice age. It has been suggested that with the rise of agriculture and towns, and increased division of labour, people could survive even if they weren’t as smart and self-sufficient as their hunter-gatherer ancestors. But smaller doesn’t necessarily mean less powerful. Brains are costly to operate, so evolution is likely to favour increased efficiency. Modern brains might do just as much – or even more – with a smaller, more efficient package.…

DEMENTIA is becoming the leading cause of death in many Western countries. Some of this is down to doctors being more willing to put dementia on death certificates, but there is also a real rise. Dementia doesn’t kill directly, but by making people frailer and less able to eat, it leaves them vulnerable to infections like pneumonia. Alzheimer’s disease is the most common form of dementia, in which people become forgetful and confused, usually starting in older age. People with Alzheimer’s have a build-up of two kinds of protein clumps in the brain: amyloid and tau. These seem to start forming in our memory centres, two small, curved structures on either side of the head called the hippocampi, before spreading all over the brain. “You are less likely to develop…

MORE than 37 million people in the US alone experience migraines, although perhaps 50 per cent of those affected, known as migraineurs, may be undiagnosed. One physiological feature of a migraine attack is a storm of neural activity called cortical spreading depression that passes in a wave across the brain’s surface. A group of researchers at Harvard Medical School was first to record this epilepsy-like activity in a brain scanner, in a visual region that responds to flickering motion. The study confirmed a long-suspected link between spreading depression and the aura that often precedes migraine pain. This process is linked to structural changes in these areas of the brain, with increased cortical thickness in visual areas associated with migraine aura. In another study from 2007, the Harvard researchers found thickening…

IN OCTOBER 2019, the Kenyan athlete Eliud Kipchoge ran a marathon in a time of 1 hour, 59 minutes and 40 seconds – the first time the fabled 2-hour threshold had been undercut. The circumstances of the race meant it didn’t count as an official record, however. Kipchoge holds that, too, with a time of 2:01:39 recorded a year earlier at the Berlin marathon. Until recently, scientists concerned with the limits of human endurance performance tended to focus on the physiological – how the body functions, in other words – and the environmental. Over the past decade, however, they have come to understand that, to a greater extent than ever previously imagined, those limits are determined by the grey lump between your ears. The brain makes the call to slow…

IF YOU could travel back in time by 2500 years or so, you would find that the great thinkers of Ancient Greece weren’t all that interested in the brain. At the time, many philosophers, Aristotle included, believed that the human mind resided in the heart and that the brain existed to cool the blood. Hippocrates, however, wasn’t convinced. He argued that the brain was in fact the seat of thought, sensation, emotion and cognition. He was eventually proved right, although achieving a deeper understanding of the brain’s anatomy and function took centuries. Many early theories ignored the solid brain tissue in favour of the brain’s fluid-filled cavities, or ventricles. The 2nd-century physician Galen believed the human brain had three ventricles, responsible for imagination, reason and memory respectively. According to his…

BIRTH alters brain function surprisingly little. The touch-sensitive somatosensory cortex is active before birth, but it is another two or three months before there is any other activity in the cortex, the brain area that ultimately governs such things as voluntary movement, reasoning and perception. The frontal lobes become active at between 6 months and a year old, triggering the development of emotions, attachments, planning, working memory and attention. A sense of self develops as the parietal and frontal lobe circuits become more integrated, at around 18 months, and a sense of other people having their own minds at age 3 to 4. Life experiences in these early years help shape our emotional well-being, and neglect or harsh parenting may change the brain for good. Maternal rejection or trauma early…

OUR capacity to remember has fascinated humans since ancient times. Plato famously compared our memory to a wax tablet that is blank at birth and slowly takes on the impression of the events from our life. We now know that individual memories are stored in groups of neurons. This idea was first proposed by psychologist Donald Hebb in 1949. Confirmation of it, and the finer details, had to wait for significant improvements in technology, however. Much of the early seminal work on memory was done in the 1960s on sea slugs. These creatures grow up to about 30 centimetres long and have giant nerve cells to match. Their outsize bodies make it possible to watch what happens when a new memory forms. Ordinarily, electrical impulses in one neuron spark the…

CONSIDER the engineer’s superior spatial intelligence and the lawyer’s command of words, and you have to wonder whether there are different types of intelligence. This question was debated ferociously during the early decades of the 20th century. Over time, it became clear that people who are good at one type of intelligence test tend to be good at all of them. This led British psychologist Charles Spearman to propose the idea of a general intelligence factor, or “g”, in the early 1900s. The g factor describes how, for example, your performance on a test of verbal ability predicts your score on one of mathematical aptitude, and vice versa. Spearman reasoned that all tests must therefore tap into some deeper, general ability, and he invented a statistical method called factor analysis…

One of the greatest scientific minds of all time ended up in 240 pieces, packed into a couple of jars, and was carted around for years in the trunk of Princeton University pathologist Thomas Harvey’s car. At the time of his autopsy in 1955 (just 7 hours after his death), Albert Einstein’s brain was reported by Harvey to appear unremarkable – it was a little shrunken with age, and slightly smaller than average. Nevertheless, Harvey carefully photographed and dissected it, and kept it preserved in formalin until science had new ways to scrutinise this amazing grey matter. In the early 1980s, neurologist Marian Diamond at the University of California, Berkeley, analysed some slides containing sections of Einstein’s brain taken from the prefrontal and parietal lobes. These areas are part of…

DIAGNOSING mental health conditions usually involves evaluating a person’s symptoms to determine which of the hundreds of conditions listed in psychiatry’s classification bible, the Diagnostic and Statistical Manual of Mental Disorders, best fits their experience. Treatment will vary depending on the condition diagnosed. But there is growing evidence that this approach may be missing something important. Instead of being separate conditions, many mental health conditions appear to share an underlying biological cause, something researchers now call the “p factor”. This has intentional parallels with one of the most famous concepts in psychology, the general intelligence or “g factor” introduced by British psychologist Charles Spearman more than a century ago. ← Turn back to page 56 for more on the g factor A century on, applying Spearman’s approach of statistical factor…

WE MAY not have recognised it, but everyone has experienced how inflammation affects the brain. The lethargy and low mood that sweep over us when sickness strikes, driving us to curl up under a duvet, is a direct consequence of the body’s response to infection or injury. On detection of a harmful stimulus, macrophages, a type of white blood cell, release signalling molecules called cytokines. These signals of inflammation rally other immune cells to the scene to help fight infection or repair damage. They also make their way to the brain, which has a separate immune system to the rest of the body, divided by the blood-brain barrier. These bodily inflammation signals trigger neuro-inflammation, courtesy of the brain’s microglial cells. These secrete furthe rcytokines, which bring about “sickness behaviours”: low…

BRAIN-SCANNING technology has provided a way to peer inside our minds and watch thoughts as they happen. Detecting the content of these thoughts is more difficult. Some researchers are now using artificial intelligence to extrapolate a person’s thoughts from their brain activity alone. AI’s algorithms excel at picking up patterns in complicated data sets, such as brain scans. Rather than being hard-coded with specific things to look out for, many AIs learn by example. This means that instead of needing to fully understand the brain, it may be possible to show AIs thousands of examples of brain scans along with details of whatever the brain was doing at the time, and for them to work out the links for themselves. ← Turn back to page 13 for more on brain-imaging…

Chances are, you have heard of the distinction between being left or right-brained – rational and logical versus creative and free-spirited – and perhaps even put yourself in one camp or the other. But appealing as this division is, it is a complete myth. It is easy to see how the idea was born. In the 1960s, we discovered that certain functions occur solely on one side of the brain. Most people process language in the left hemisphere of the cortex, whereas our emotions are dealt with in the right. It was soon said that our left hemisphere held a monopoly over the virtues of logic, reason and language. The right side of the brain was responsible for driving our emotions, musicality and impulsiveness. From this came the popular maxim…

AGEING inevitably brings changes to the human brain. There is some decline in the blood vessels servicing it, and in the quantity of myelin, the fatty material that insulates the nerve fibres. The brain reduces slightly in volume. We lose cells in critical areas such as the hippocampus, where memories are processed. From the age of 40, our brains begin to shrink at a rate of 5 per cent per decade. The process seems to accelerate after the age of 70. It affects the entire brain, although some regions seem especially vulnerable. Meanwhile, as we age, the grooves all over the brain’s surface widen, and there is a slight expansion of its fluid-filled cavities (called ventricles). Age also reduces the speed at which nerve signals travel, and there is a…

IN THE Harry Potter films, memories are silver streams that can be teased from the head with the tip of a wand. In the Pixar movie Inside Out, they are small glowing balls, stored in vast racks of shelving in our minds. A major step towards our modern understanding of where memories are formed and stored in the brain came from one of the saddest tales of modern neuroscience. In 1953, Henry Molaison – known in countless research papers by his initials, H.M. – had an operation that went badly wrong. The surgeon had been trying to remove brain tissue that was causing his epilepsy. Molaison’s seizures originated in the hippocampi, a pair of structures at either side of the brain whose Latin name reflects their supposed resemblance to a…

We all have memories we would rather forget – and it is possible, if you try hard enough. Research suggests that, while we think of memories as something you can actively strengthen but of forgetting as a passive process, in reality, forgetting can be deliberate, too. Perhaps the easiest way to forget something is simply to try to suppress a memory. Researchers at Dartmouth College, New Hampshire, have found that just telling people to “push thoughts out of their head” is enough to make them forget lists of words they have learned to associate with particular cues. This seems especially paradoxical because we also know that rehearsing memories helps to strengthen them. Suppression has been linked to decreased activity in the hippocampus, so one idea is that we may be…

IT IS obvious why our brains would have a highly developed system for dealing with perceived threats – in an evolutionary sense, recognising threats and responding appropriately is the difference between surviving and not. Central to it all is the amygdala, a brain region that processes our emotions and triggers the release of the hormones responsible for the fight-or-flight response. The amygdala is linked to parts of the prefrontal cortex and another area, the anterior cingulate cortex, that process social information and help us make decisions (see diagram, right). During bouts of everyday anxiety, this brain circuit switches on and then off again – but Oliver Robinson at University College London and his colleagues have shown that in people with anxiety disorders, it seems to get stuck in the on…

There are many hard problems in science, but only one of them gets to call itself “the hard problem”. We are still a country mile away from understanding the nature of conscious experience and how it arises in the brain. While the brain is a physical entity, consciousness was long thought to be something different, non-physical and immeasurable. But neuroscientists have challenged this idea. Today, most people accept that consciousness is a product of the electrical activity of the brain. The unanswered question, then, is how it arises. One idea is global workspace theory. It suggests that information from the outside world competes for attention in the cortex and the thalamus. If the signal it generates outcompetes other information, it is broadcast across the brain. Only then do you consciously…

SUPERHUMAN memory has a special appeal. Who could resist the idea of remembering everything they wanted to, without trying? Learning would be made easy, exams a breeze and you would never forget where you left your keys. And memory-related disorders like Alzheimer’s disease would have met their match. So it is of little surprise that scientists have turned their attention to ways of enhancing human memory using techniques that stimulate, supplement or even mimic parts of the brain. The immediate goal is to treat memory disorders, but the idea of a memory prosthesis for everyday life is also gaining ground. One approach is deep brain stimulation (DBS), which involves zapping an affected brain area with an implanted electrode. This is already used in the treatment of Parkinson’s disease and epilepsy,…