The Brain: The Story of You

by David Eagleman

In the brain’s microscopically small circuitry is etched the history and future of our species.

we’re so trapped inside our reality that it is inordinately difficult to realize we’re trapped inside anything.

An entire life, lavishly colored with agonies and ecstasies, took place in these three pounds.

the human brain is born remarkably unfinished.

a human brain allows itself to be shaped by the details of life experience. This leads to long periods of helplessness as the young brain slowly molds to its environment. It’s “livewired”.

Just like paths in a forest, you lose the connections that you don’t use.

You become who you are not because of what grows in your brain, but because of what is removed.

We hooked them up with a device to measure the galvanic skin response (GSR), a useful proxy for anxiety: the more your sweat glands open, the higher your skin conductance will be. (This is, by the way, the same technology used in a lie detector, or polygraph test.)

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.

areas involved in social considerations (such as the mPFC) are more strongly coupled to other brain regions that translate motivations into actions (the striatum and its network of connections).

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 were particularly interested in a small area of the brain called the hippocampus – vital for memory, and, in particular, spatial memory.

Your family of origin, your culture, your friends, your work, every movie you’ve watched, every conversation you’ve had – these have all left their footprints in your nervous system. These indelible, microscopic impressions accumulate to make you who you are, and to constrain who you can become.

amygdala, which is involved in fear and aggression.

Your memory of who you were at fifteen is different to who you actually were at fifteen; moreover, you’ll have different memories that relate back to the same events.

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.

The enemy of memory isn’t time; it’s other memories.

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.

During sleep, neurons simply coordinate with one another differently, entering a more synchronized, rhythmic state.

Consciousness emerges when neurons are coordinating with one another in complex, subtle, mostly independent rhythms. In slow-wave sleep, neurons are more synchronized with one another, and consciousness is absent.

The philosopher René Descartes assumed that an immaterial soul exists separately from the brain. His speculation, depicted in the figure, was that sensory input feeds into the pineal gland, which serves as the gateway to the immaterial spirit. (He most likely chose the pineal gland simply because it sits on the brain’s midline, while most other brain features are doubled, one on each hemisphere.)

You don’t perceive objects as they are. You perceive them as you are.

As your trillions of new connections continually form and re-form, the distinctive pattern means that no one like you has ever existed, or will ever exist again. The experience of your conscious awareness, right now, is unique to you.

From cradle to grave, we are works in progress.

Visual data goes through more complex processing than auditory data. It takes longer for signals carrying flash information to work their way through the visual system than for bang signals to work through the auditory system.

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.

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.

saccades.

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.

The slice of reality that we can see is limited by our biology.

No one is having an experience of the objective reality that really exists; each creature perceives only what it has evolved to perceive.

The real world is not full of rich sensory events; instead, our brains light up the world with their own sensuality.

Synesthesia is a condition in which senses (or in some cases concepts) are blended.

Synesthesia shows us that even microscopic changes in brain wiring can lead to different realities.

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

reality is a narrative played out inside the sealed auditorium of the cranium.

amygdala

Our time distortion is something that happens in retrospect, a trick of the memory that writes the story of our reality.

position of one’s own limbs (known as proprioception).

different types of brain waves: Delta waves (below 4 Hz) occur during sleep; Theta waves (4–7 Hz) are associated with sleep, deep relaxation, and visualization; Alpha waves (8–13 Hz) occur when we are relaxed and calm; Beta waves (13–38 Hz) are seen when we are actively thinking and problem solving. Other ranges of brain waves have been identified as important since then, including Gamma waves (39–100 Hz) which are involved in concentrated mental activity, such as reasoning and planning.

When we practice new skills, they become physically hardwired, sinking below the level of consciousness.

We all know the feeling of driving home along your daily route and suddenly realizing you’ve arrived with no real memory of the drive. The skills involved in driving have become so automatized that you can run the routines unconsciously. The conscious you – the part that flickered to life when you woke up in the morning – is no longer the driver, but at best a passenger along for the ride.

There’s an interesting upshot to automatized skills: attempts to consciously interfere with them typically worsen their performance. Learned proficiencies – even very complex ones – are best left to their own devices.

Sigmund Freud entered medical school in Vienna in 1873, and specialized in neurology. When he opened his private practice for the

treatment of psychological disorders, he realized that often his patients had no conscious knowledge of what was driving their behavior. Freud’s insight was that much of their behavior was a product of unseen mental processes. This simple idea transformed psychiatry, ushering in a new way of understanding human drives and emotions.

His method was to gather information in patterns of behavior, in the content of dreams, in slips of the tongue, in mistakes of the pen.

He became convinced that the conscious mind is the tip of the iceberg of our mental processes, while the much larger part of what drives our thoughts and behaviors lies hidden from view.

one consequence is that we don’t typically know the roots of our own choices.

This view of governance is called soft paternalism, and Thaler and Sunstein believe that gently guiding the unconscious brain has a far more powerful influence on our decision making than outright enforcement ever can.