The Brain: The Story of You

by David Eagleman

As an example, the language that you’re exposed to in infancy (say, English versus Japanese) refines your ability to hear the particular sounds of your language, and worsens your capacity to hear the sounds of other languages. That is, a baby born in Japan and a baby born in America can hear and respond to all the sounds in both languages. Through time, the baby raised in Japan will lose the ability to distinguish between, say, the sounds of R and L, two sounds that aren’t separated in Japanese. We are sculpted by the world we happen to drop into.

When the team began their research, they expected to find a clear-cut link between cognitive decline and the three diseases that are the most common causes of dementia: Alzheimer’s, stroke and Parkinson’s. Instead, here’s what they found: having brain tissue that was being riddled with the ravages of Alzheimer’s disease didn’t necessarily mean a person would experience cognitive problems. Some people were dying with a full-blown Alzheimer’s pathology without having cognitive loss. What was going on? The team went back to their substantial data sets for clues. Bennett found that psychological and experiential factors determined whether there was loss of cognition. Specifically, cognitive exercise – that is, activity that keeps the brain active, like crosswords, reading, driving, learning new skills, and having responsibilities – was protective. So were social activity, social networks and interactions, and physical activity. On the flip side, they found that negative psychological factors like loneliness, anxiety, depression, and proneness to psychological distress were related to more rapid cognitive decline. Positive traits like conscientiousness, purpose in life, and keeping busy were protective. The participants with diseased neural tissue – but no cognitive symptoms – have built up what is known as “cognitive reserve”. As areas of brain tissue have degenerated, other areas have been well exercised, and therefore have compensated or taken over those functions. The more ...

How does the biological wetware of the brain give rise to our experience: the sight of emerald green, the taste of cinnamon, the smell of wet soil? What if I told you that the world around you, with its rich colors, textures, sounds, and scents is an illusion, a show put on for you by your brain? If you could perceive reality as it really is, you would be shocked by its colorless, odorless, tasteless silence. Outside your brain, there is just energy and matter. Over millions of years of evolution the human brain has become adept at turning this energy and matter into a rich sensory experience of being in the world. How?

So what does the world outside your head really “look” like? Not only is there no color, there’s also no sound: the compression and expansion of air is picked up by the ears, and turned into electrical signals. The brain then presents these signals to us as mellifluous tones and swishes and clatters and jangles. Reality is also odorless: there’s no such thing as smell outside our brains. Molecules floating through the air bind to receptors in our nose and are interpreted as different smells by our brain. The real world is not full of rich sensory events; instead, our brains light up the world with their own sensuality.

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. Why does this happen? Because the brain mechanisms for judging intrapersonal warmth overlap with the mechanisms for judging physical warmth, and so one influences the other. The upshot is that your opinion about something as fundamental as your relationship with your mother can be manipulated by whether you take your tea hot or iced. Similarly, when you are in a foul-smelling environment, you’ll make harsher moral decisions – for example, you’re more likely to judge that someone else’s uncommon actions are immoral. 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.

Because the brain has no pain receptors, a patient can be awake during a surgery.

With the proper brain-machine interface and wireless technology, there’s no reason you couldn’t control large devices such as a crane or a forklift wirelessly, at a distance, with your thoughts, in the same way that you might absent-mindedly dig with a trowel or play a guitar. Your capacity to do this well would be enhanced by sensory feedback, which could be done visually (you watch how the machine moves), or even by feeding data back into your somatosensory cortex (you feel how the machine moves). Controlling such limbs would take practice and be awkward at first, in the same way that a baby has to flail for some months to learn how to finely control its arms and legs. With time, these machines would effectively become an extra limb – one that could have extraordinary strength, hydraulic or otherwise. They would come to feel the way that your arms or legs do to you now. They would just be another limb – simple extensions of ourselves. We don’t know of a theoretical limit on the kinds of signals brain could learn to incorporate.

It’s not difficult to see why reconstructing the full picture of all the connections in a human brain is such a daunting task, and one that we have no real hope of accomplishing anytime soon. The amount of data required is gargantuan: to store a high-resolution architecture of a single human brain would require a zettabyte of capacity. That’s the same size as all the digital content of the planet right now.

With every attempt to simulate or create a human-like intelligence, we’re confronted by a central unsolved question of neuroscience: how does something as rich as the subjective feeling of being me – the sting of pain, the redness of red, the taste of grapefruit – arise from billions of simple brain cells running through their operations? After all, each brain cell is just a cell, following local rules, running its basic operations. By itself, it can’t do much. So how do billions of these add up to the subjective experience of being me?