The Brain: The Story of You

by David Eagleman

The surprise is that a faded memory doesn’t seem faded to you. You feel, or at least assume, that the full picture is there.

And your memory of the event is even more dubious. Say that in the intervening year since the dinner, your two friends have split up. Thinking back on the dinner, you might now misremember sensing red flags. Wasn’t he more quiet than usual that night? Weren’t there moments of awkward silence between the two?

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?

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 ...

the brain is just as active at night as during the day. During sleep, neurons simply coordinate with one another differently, entering a more synchronized, rhythmic state. Imagine the crowd at the stadium doing an incessant Mexican wave, around and around.

there is no room between cells in the brain – they are packed tightly against one another.

Everything you experience – every sight, sound, smell – rather than being a direct experience, is an electrochemical rendition in a dark theater. How does the brain turn its immense electrochemical patterns into a useful understanding of the world? It does so by comparing the signals it receives from the different sensory inputs, detecting patterns that allow it to make its best guesses about what’s “out there”.

what happens when you clap your hands in front of you. Try it. Everything seems synchronized. How can that be, given that sound is processed more quickly? What it means is that your perception of reality is the end result of fancy editing tricks: the brain hides the difference in arrival times. How? What it serves up as reality is actually a delayed version. Your brain collects up all the information from the senses before it decides upon a story of what happens.

These timing difficulties aren’t restricted to hearing and seeing: each type of sensory information takes a different amount of time to process. To complicate things even more, even within a sense there are time differences. For example, it takes longer for signals to reach your brain from your big toe than it does from your nose. But none of this is obvious to your perception: you collect up all the signals first, so that everything seems synchronized.

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.

Detailed expectations about the world – in other words, what the brain “guesses” will be out there – are being transmitted by the visual cortex to the thalamus. The thalamus then compares what’s coming in from

the eyes. If that matches the expectations (“when I turn my head I should see a chair there”), then very little activity goes back to the visual system. The thalamus simply reports on differences between what the eyes are reporting, and what the brain’s internal model has predicted. In other words, what gets sent back to the visual cortex is what fell short in the expectation (also known as the “error”): the part that wasn’t predicted away.

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 electrical fields.

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.

schizophrenia was described as an intrusion of the dream state into the waking state.

They reported the numbers they were able to read on the device strapped to their wrists. If they really could see time in slow motion they would be able to read the numbers. But no one could.

No one’s in-flight performance was better than their ground-based performance. Despite initial hopes, we were not like Neo.

So why do Jeb and I both recall our accidents as happening in slow motion? The answer appears to lie in the way our memories are stored.

In threatening situations, an area of the brain called the amygdala kicks into high gear, commandeering the resources of the rest of the brain and forcing everything to attend to the situation at hand. When the amygdala is in play, memories are laid down with far more detail and richness than under normal circumstances; a secondary memory system has been activated. After all, that’s what memory is for: keeping track of important events, so that if you’re ever in a similar situation, your brain ...

The same behind-the-scenes work is true of ideas. We take conscious credit for all our ideas, as though we’ve done the hard work in generating them. But in fact, your unconscious brain has been working on those ideas – consolidating memories, trying out new combinations, evaluating the consequences – for hours or months before the idea rises to your awareness and you declare, “I just thought of something!”

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

the two hemispheres are connected by a super-highway of nerves called the corpus callosum, and this allows the right and left halves to coordinate and work in concert.

be. The key to the 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.