The Brain: The Story of You

by David Eagleman

Which synapses stay and which go? When a synapse successfully participates in a circuit, it is strengthened; in contrast, synapses weaken if they aren’t useful, and eventually they are eliminated. Just like paths in a forest, you lose the connections that you don’t use.

It's a great analogy and can help us getting better insights from it.

Nelson explains that he’d walk into a room and be surrounded by little kids he’d never seen before – and they’d want to jump into his arms and sit on his lap or hold his hand or walk off with him. Although this sort of indiscriminate behavior seems sweet at first glance, it’s a coping strategy of neglected children, and it goes hand-in-hand with long-term attachment issues. It is a hallmark behavior of children who have grown up in an institution.

Only a couple of decades ago it was thought that brain development was mostly complete by the end of childhood. But we now know that the process of building a human brain takes up to twenty-five years.

Volunteers sat in a shop window, to be stared at by passersby. Teenagers have greater social anxiety than adults, reflecting the details of brain development during the adolescent years.

Beyond social awkwardness and emotional hypersensitivity, the teen brain is set up to take risks. Whether it’s driving fast or sexting naked photos, risky behaviors are more tempting to the teen brain than to the adult brain. Much of that has to do with the way we respond to rewards and incentives.

For frustrated parents the world over, there’s an important message: who we are as a teenager is not simply the result of a choice or an attitude; it is the product of a period of intense and inevitable neural change.

The scientists discovered visible differences in the cabbies’ brains: in the drivers, the posterior part of the hippocampus had grown physically larger than those in the control group – presumably causing their increased spatial memory. The researchers also found that the longer a cabbie has been doing his job, the bigger the change in that brain region, suggesting that the result was not simply reflecting a pre-existing condition of people who go into the profession, but instead resulted from practice.

Shortly after killing his wife and his mother, he’d sat down and typed what amounted to a suicide note: I don’t really understand myself these days. I am supposed to be an average reasonable and intelligent young man. However, lately (I cannot recall when it started) I have been a victim of many unusual and irrational thoughts . . . After my death I wish that an autopsy would be performed on me to see if there is any visible physical disorder. Whitman’s request was granted. After an autopsy, the pathologist reported that Whitman had a small brain tumor. It was about the size of a nickel, and it was pressing against a part of his brain called the amygdala, which is involved in fear and aggression. This small amount of pressure on the amygdala led to a cascade of consequences in Whitman’s brain, resulting in him taking actions that would otherwise be completely out of character. His brain matter had been changing, and who he was changed with it.

Imagine a person could be split into herself at all her different ages. Would they all agree on the same memories? If not, are they really the same person?

Rather than memory being an accurate video recording of a moment in your life, it is a fragile brain state from a bygone time that must be resurrected for you to remember.

One of neuroscience’s unsolved puzzles is known as the “binding problem”: how is the brain able to produce a single, unified picture of the world, given that vision is processed in one region, hearing in another, touch in another, and so on?

Vision isn’t about photons that can be readily interpreted by the visual cortex. Instead it’s a whole body experience. The signals coming into the brain can only be made sense of by training, which requires cross-referencing the signals with information from our actions and sensory consequences. It’s the only way our brains can come to interpret what the visual data actually means.

Completely isolated from the outside world, with no sound and no light, Luke’s eyes and ears were completely starved of input. But his mind didn’t abandon the notion of an outside world. It just continued to make one up. Luke describes the experience: “I remember going on these trips. One I used to remember was flying a kite. It got pretty real. But they were all in my head.” Luke’s brain continued to see.

In fact, the brain generates its own reality, even before it receives information coming in from the eyes and the other senses. This is known as the internal model.

Visual information travels from the eyes to the lateral geniculate nucleus to the primary visual cortex (gold). Strangely, ten times as many connections feed information back in the other direction (purple).

Twenty percent of the calories we consume are used to power the brain. So brains try to operate in the most energy-efficient way possible, and that means processing only the minimum amount of information from our senses that we need to navigate the world.

Color is an interpretation of wavelengths, one that only exists internally.

Synesthesia is a condition in which senses (or in some cases concepts) are blended. There are many different kinds of synesthesia. Some taste words. Some see sounds as colors. Some hear visual motion. About 3% of the population has some form of synesthesia.

Austin’s talent and speed is the end result of physical changes in his brain. During his years of practice, specific patterns of physical connections have formed. He has carved the skill of cup stacking into the structure of his neurons. As a consequence, Austin now expends much less energy to stack cups. My brain, in contrast, is attacking the problem by conscious deliberation. I’m using general-purpose cognitive software; he’s transferred the skill into specialized cognitive hardware.

Take an effect called “priming”, in which one thing influences the perception of something else. For example, if you’re holding a warm drink you’ll describe your relationship with a family member more favorably; when you’re holding a cold drink, you’ll express a slightly poorer opinion of the relationship.

In another study, it was shown that if you sit in a hard chair you’ll be a more hard-line negotiator in a business transaction; in a soft chair you’ll yield more.

Kenneth Parks leaves the courtroom, a free man after killing his in-laws. His lawyer, Marlys Edwardh, said: “The verdict was stunning … It was a moral vindication for Ken. The judge said he was free to go.”

Even after an experimenter manipulates a choice by stimulating the brain, participants often claim that their decision was freely chosen.

Ping pong balls on mouse traps follow physical rules. But where they end up is impossible to predict in practice. Similarly, your billions of brain cells and their trillions of signals interact every second. Although it’s a physical system, we could never predict precisely what is going to happen next.

Unlike computers, the brain runs on conflict between different possibilities, all of which try to out-compete the others. And there are always multiple options. Even after you’ve selected mint or lemon, you find yourself in a new conflict: should you eat the whole thing? Part of you wants the delicious energy source, and at the same time part of you knows it’s sugary, and perhaps you should be jogging instead. Whether you polish off the whole container is simply a matter of the way the infighting goes.

we’re caught in a conflict between two systems that have different opinions. Our rational networks tell us that one death is better than four, but our emotional networks trigger a gut feeling that murdering the bystander is wrong. You’re caught between competing drives, with the result that your decision is likely to change entirely from the first scenario.

When a person hits the button to launch a long-range missile, it involves only the networks involved in solving logical problems. Operating a drone can become like a video game; cyber attacks wreak consequences at a distance. The rational networks are at work here, but not necessarily the emotional networks. The detached nature of distance warfare reduces internal conflict, making it easier to wage.

Because the conscious mind has low bandwidth, you don’t typically have full access to the bodily signals that tip your decisions; most of the action in your body lives far below your awareness.

The power of now explains why people make decisions that feel good in the moment but have lousy consequences in the future:

Ulysses desperately wanted to hear the legendary songs, but he didn’t want to kill himself and his crew. So he hatched a plan. He knew that when he heard the music, he would be unable to resist steering toward the island’s rocks. The problem wasn’t the present rational Ulysses, but instead the future, illogical Ulysses – the person he’d become when the Sirens came within earshot. So Ulysses ordered his men to lash him securely to the mast of the ship. They filled their ears with beeswax so as not to hear the Sirens, and they rowed under strict orders to ignore any of his pleas and cries and writhing. Ulysses knew that his future self would be in no position to make good decisions. So the Ulysses of sound mind arranged things so that he couldn’t do the wrong thing. This sort of deal between your present and future self is known as a Ulysses contract.

Ulysses contract is recognizing that we are different people in different contexts. To make better decisions, it’s important not only to know yourself but all of your selves.

Some psychologists describe this effect as “ego-depletion,” meaning that higher-level cognitive areas involved in executive function and planning (for example, the prefrontal cortex) get fatigued. Willpower is a limited resource; we run low on it, just like a tank of fuel. In the case of the judges, the more cases they had to make decisions about (up to thirty-five in one sitting) the more energy-depleted their brains became. But after eating something like a sandwich and a piece of fruit, their energy stores were refueled and different drives had more power in steering decisions.

Consider the choice of monogamy – bonding and staying with a single partner. This would seem like a decision that involves your culture, values, and morals. All that is true, but there’s a deeper force acting on your decision making as well: your hormones. One in particular, called oxytocin, is a key ingredient in the magic of bonding. In one recent study, men who were in love with their female partners were given a small dose of extra oxytocin. They were then asked to rate the attractiveness of different women. With the extra oxytocin, the men found their partners more attractive – but not other women. In fact, the men kept a bit more physical distance from an attractive female research associate in the study. Oxytocin increased bonding to their partner.

Some networks in the brain are involved in craving (red); others in suppressing the temptation (blue). Using real-time feedback in neuroimaging, we measure the activity in the two networks and give a participant visual feedback about how well they’re fighting the battle.

Although we typically feel independent, each of our brains operates in a rich web of interaction with one another – so much so that we can plausibly look at the accomplishments of our species as the deeds of a single, shifting mega-organism.

On average, those with Botox were worse at identifying the emotions in the pictures correctly. Why? One hypothesis suggests that the lack of feedback from their facial muscles impaired their ability to read other people. We all know that the less mobile faces of Botox users can make it hard to tell what they’re feeling; the surprise is that those same frozen muscles can make it hard for them to read others. Here’s a way to think about this result: my facial muscles reflect what I’m feeling, and your neural machinery takes advantage of that. When you’re trying to understand what I’m feeling, you try on my facial expression. You don’t mean to do it – it happens rapidly and unconsciously – but that automatic mirroring of my expression gives you a rapid estimate of what I’m likely to be feeling.

Consider the case of a young girl named Cameron Mott. At the age of four she began to have violent seizures. The seizures were aggressive: Cameron would suddenly drop to the floor, requiring her to wear a helmet all the time. She was quickly diagnosed with a rare and debilitating disease called Rasmussen’s Encephalitis. Her neurologists knew that this form of epilepsy would lead to paralysis and eventually to death – and so they proposed a drastic surgery. In 2007, in an operation that took almost twelve hours, a team of neurosurgeons removed an entire half of Cameron’s brain.

As it turns out, the consequences were surprisingly slight. Cameron is weak on one side of her body, but otherwise she’s essentially indistinguishable from the other children in her class. She has no problems understanding language, music, math, stories. She’s good in school and she participates in sports. How could this be possible? It’s not that one half of Cameron’s brain was simply not needed; instead, the remaining half of Cameron’s brain dynamically rewired to take over the missing functions, essentially cramming all the operations into half the brain space. Cameron’s recovery underscores a remarkable ability of the brain: it rewires itself to adjust to the inputs, outputs, and tasks at hand.

In this critical way, the brain is fundamentally unlike the hardware in our digital computers. Instead, it’s “liveware”. It reconfigures its own circuitry. Although the adult brain isn’t quite as flexible as a child’s, it still retains an astonishing ability to adapt and change.

The electrical storms in her cortex are monitored, translated on a computer to understand the intention, and the output is used to control the world’s most advanced robotic arm.