This was a really nice companion read to When Breath Becomes Air, which provided more of the philosophical side to the science and research found here. It struck a nice balance between detail and simplicity, with enough case studies added in for more of a personal touch.

In The Brain: The Story of You, David Eagleman unpacks what science can and cannot tell us about how our minds work and make us who we are. What we do know: who we are is a combination of nature and nurture - what happens in our childhood has profound implications on how our brains are structured and wired. Yet, the brain demonstrates plasticity in adulthood - our adult experiences can also re-sculpt and transform the brain profoundly, as demonstrated by the brain changes in London cabbies.

Second, even for actions that look and feel effortless (drinking a cup of coffee, walking down the street, reading - once you've mastered that skill) the unconscious machinery of our brains is working fast and furiously. Throughout our lives, "our brains rewrite themselves to build dedicated circuitry for the missions we practice - whether that's walking, juggling, swimming or driving....[these] new skills sink below the reach of conscious access."

Third, the directionality of the relationship between our sense of self and identity and our memories is not clear. Is our sense of self derived from our memories? Do we begin to construct a personal narrative from our different experiences and encounters? Or does our sense of self shape our memories? Eagleman points out that our memories are fallible and that "you can't help but have your present colour your past. So a single event may be perceived somewhat differently by you at different stages in your life."

Fourth, "conscious awareness is one of the most baffling puzzles of modern neuroscience". We can examine the physical brain and map out the mechanics of different neurons, what is going on in different regions of the brain and how they connect. What we do not know is "why all those signals coursing around in there mean anything to us". Eagleman notes that "you don't perceive objects as they are. You perceive them as you are", ascribing meaning to them based on our genes and personal experiences. So when I look at an image of an Italian flag or a cat, the meaning I ascribe to it will be different from the meaning another individual ascribes to it.

Fifth, reality isn't what we think it is. (This was probably the most mind blowing section for me.) Although we think that there is an objective reality - that car is red, that is the sound of a bird chirping, that is the smell of trash - all these sensory experiences, "rather than being a direct experience, [are] an electrochemical rendition in a dark theatre." Seeing is not just about what the eyes take in and the brain interpreting the input from the eyes. Vision is "a whole body experience" where the signals coming into the brain can only be made sense of through training. When a baby first opens its eyes, it needs to learn how to interpret all that visual data - if I move closer to this object, what happens? If I reach out and close my hands on this, what happens? Babies are learning that when they undertake certain actions, it changes the sensory input that returns. Soon, the brain establishes patterns to process and make sense of all that input. Because there is so much visual data in the world, the brain learns to make assumptions about what it sees and what to expect from its internal model developed from years of training. [This is why when you look at the back of a 3D mask, it looks as those the face is popping out - your internal model has been trained on a lifetime of faces that stick out. Your internal model also assumes that the world outside is stable, which is why the world appears stable even though your eyes jump around about four times a second in saccades.] Eagleman points out that "each creature picks up on its own slice of reality. In the blind and deaf world of the tick, the signals it detects from its environment are temperature and body odour. For bats, it's the echolocation of air compression waves. For the black ghost knifefish, its experience of the world is defined by perturbations in electric fields. These are the slices of their ecosystem that they can detect. No one is really having an experience of the objective reality that really exists; each creature perceives only what it has evolved to perceive. But presumably, every creature assumes its slice of reality to be the entire objective world...Not only is there no colour, 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 tons 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." So depending on how our brains are wired, our experience of "reality", those molecules and wavelengths and waves in the air, can be very different, as the experience of synthetes and schizophrenics shows. Mind blowing.

There are little nuggets scattered throughout the book that help you understand why certain things are the way they are. Why are the teenage years so difficult, for instance? Eagleman explains that during the teenage years, the medial prefrontal cortex becomes very active in social situations, causing "social situations [to] carry a lot of weight, resulting in a self-conscious stress response of high intensity....Beyond social awkwardness and emotional hypersensitivity, the teen brain is set up to take risks....the brain shows an increasing response to rewards in areas related to pleasure seeking...the activity here is as high as it is in adults....[yet] activity in the orbitofrontal cortex - involved in executive decision making, attention, and simulating future consequences - is still about the same in teens as it is in children. A mature pleasure-seeking system coupled with an immature orbitofrontal cortex means that teens are not only emotionally hypersensitive but also less able to control their emotions than adults.

Highly accessible and highly recommended if you've any interest in neuroscience.

This book had some interesting things in it, but the tone and content is a little too tilted to the popular side of the popular science genre for me. I felt entertained by factual information, but it didn't quite rise to the level of making me feel educated on the subject.

Quite simply an incredible book. Written in fully accessible language, Eagleman gives a ridiculously thought-provoking account of what we know about the brain, how that translates into “us” and our reality, what we still desire to know about it all, and where all this knowledge could take us in the future.