The Brain

Summary

The Brain by David Eagleman dives deep into how our brains work, covering key insights of neuroscience, that tell the fascinating story of what makes us us. It is a story about how our brains are re-wiring themselves constantly, and how who we are is dependant on our past experiences, and adjusted and re-evaluated constantly. The brain is a continual learning machine, always pruning what is not needed and reinforcing what is, adapting to new patterns in the environemnt with novel forms of behavior and improving how we deal with the world and what we encounter in it, trying to make sense of it all, to survive and thrive.

What we remember is part of our personalities, but it often isn't accurate. Because what we remember already shapes how we remember new things, and how we perceive ourselves, changes what we remember in the first place. Remembering is a highly selective act and does not faithfully reproduce what happened, but more how we feel about it, what we consider important and what we paid attention too. Even perception itself, is not free from the influence of our brains. How we perceive the world around us is changed by our beliefs, by our past experiences, and the actual states of our brains in any given moment.

We literally see the world with different eyes, because of the exact circumstances that we have encountered in the past, our genetics and what we have learned about the world. We are a product of our environments, our genes and ancestry and our experiences. Eagleman even wonders what it would be like to unlock completely novel senses, how our brains can make sense of arbitrary data and how you could, at least in theory, hook up a completely novel stream of data to the brain of children and they would somehow learn to understand it, to manipulate it and make sense of it. Because that's just what happens with all the other senses anyways. Thomas Nagel asked what would it feel like to be a bat? And David Eagleman asks, what does it feel like to be directly hooked up to stock market data or the internet?

From there he conjectures how such a new sense might feel like, asking the critical question of what consciousness and qualitative experiences really are and showing ultimately that the inside of the brain is a dark, colorless, smell-less, silent place, where only electrical activity zap around between neurons and nothing else "really happens". But this electrical activity, this buzzing has meaning to us. It is us and our conscious state originates, somehow, from that activity. Furthermore, consciousness has to be constructed after the fact, because different sensory information gets to the brain at different speeds, touch from the nose has to travel a shorter distance then touch from a finger, and yet, when we touch our finger to our nose, it feels instantanteous like the two happen at the same time. Consciousness is delayed.

The book even dives into the topic of addiction, and how this constant re-wiring of brains can go wrong and lead to undesirable states, where a particular behavior becomes so strongly automated, that we lose control and the free choices that we can otherwise make collapse into repeating the same action over and over again, without being able to resist it.

Detailed Notes

All the experiences in your life - from single conversations to your broader culture - shape the microscopic details of your brain. Neurally speaking, who you are, depends on where you've been.

Just like paths in a forest you use the connections you don't use.

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

Human brains come unequipped to deal with the world, they are live wiring, therefore more adaptable to new circumstances. Most connections become important because other less important ones are pruned, newborns are just building up lots of connections and the development then consists of taking only the good ones into account and killing the rest for making decisions. This is what live wiring is. The constant formation and pruning and re-weighing of neural connections.

Orphaned children in Romania show that without early stimulation in the form of love and care a human brain can not develop properly. Here it becomes crystal clear what it means that the inside depends on the outside, otherwise normal children become mentally retarded, simply because they are not cared for.

The shaping of circuits during the teen years sets us up for the lessons we learn on our paths to becoming adults.

Teenagers develop a sense of self. Self-consciousness especially in the social world, teens are more prone to think about and have emotional responses about what other people might think, they are also more likely to do risky behaviors because their prefrontal cortex isn't fully developed yet, and only matures later in adolescence. Stimulus to do things is high, control low.

You might think that who we are as adults, is now fixed in place, immovable. But it's not: in adulthood, our brains continue to change.

Experience changes the brain, for example of cab drivers with bigger spatial memory brain areas and violin and piano players with bigger representations for movements of fingers.

Although most of the changes are too small to detect with the naked eye, everything you've experienced has altered the physical structure of your brain - from the expression of genes to the positions of molecules to the architecture of neurons.

It's not just illness or chemicals that change us: from the movies we watch to the jobs we work, everything contributes to a continual reshaping of the neural networks we summarize as us. So who exactly are you? Is there anyone down deep, at the core?

The problem of continuity - atoms are replaced every 7 years, what makes you, you then? Memory? The answer is no, since memory is fleeting, fading, shifting, and changing over time. It is fallible and altered by the present moments since it is fundamentally only neurons wiring in certain ways, but those wirings change because the neurons also participate in the formation of different new memories and they also change in light of new facts, overwriting parts of the memory with new data so to speak, leading to a fragmented, unreliable, constructed piece of data that we call memory. Even worse, those pieces can be partly or completely imaginary. And we don't even notice that we invented our memories.

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.

Our past is not a faithful record. Instead, it's a reconstruction, and sometimes it can border on mythology.

The hippocampus does not only remember things but also imagines the future, by combining "remembered" things into a coherent picture of what might happen.

Alzheimer's is depending on the circumstances, memory loss only happens when the brain is in a bad environment so to speak and the toolbox of the brain atrophies. Otherwise, it can find routes around problematic areas, by forming new connections, enabling patients to keep doing old tasks and remember things, even though they have Alzheimer's pathology.

When I think about who I am, there's one aspect above all that can't be ignored: I am a sentient being. I experience my existence. I feel like I'm here, looking out ob the world through these eyes, perceiving this Technicolor show from my own center stage. Let's call this feeling consciousness or awareness.

So who you are, at any given moment, depends on the detailed rhythms of your neuronal firing.

When asleep, the brain stays active, but still, we lose consciousness, the fact is that the kind of pattern of activity changes, from almost random, highly complex chattering, to organized rhythmical waves of activity. Without the complex chattering, we are not there. Furthermore, the way we see the world is influenced by the intricate details of this chattering of neurons. When we see something that is not how we see it, because it goes through our filter, being seen in a way that corresponds to our particular dance of neurons. And what we see influences this dance and on and on in a complex feedback loop. Making everyone uniques, changing from moment to moment into new uniques depending on what is happening in one's life.

So who you are, depends on what your neurons are up to, moment by moment.

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

Brains are as unique as snowflakes.

We're not fixed. From the cradle to the grave, we are works in progress.

What if I told you that the world around you, with its rich colors, textures, sounds, and scents us an illusion, a show put on for you by your brain? If you could perceive reality as it 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?

Optical and other forms of sensory illusions can serve as a gateway to understand that what we perceive of reality is not reality itself, but a subject experience our brains conjure up from input data it gets about reality. Our brains construct our reality and therefore it is different from what actual reality must be like. Accessing how accurate our representation, our subjective version of reality is to the real thing is something that might very well be impossible.

Seeing isn't happening in your eyes; hearing isn't taking place in your ears; smell isn't happening in your nose. all of your sensory experiences are taking place in storms of activity within the computational material of your brain.

Your brain has never directly experienced the external world, and it never will.

Example of Mike, a blind man who regained vision after a new type of surgical operation, Mike can now see but can still not see. To make sense from the vast output our sensory organs give us, we need certain patterns of connections to be formed within the brain, interpreting the data from raw format into something useable. Without those brain regions we see, yet don't see. The pure data is nonsense to us.

Vision isn't about photons that can be readily interpreted by the visual cortex. Instead it's a whole body experience.

Vision is an integrated sense, that means the data it generates is matched against that of other senses to build a coherent map of the world. That's why movement and exploration in response to visual stimuli is so important, it's necessary so the brain can update the mappings between in and output correctly across different types of sensory stimuli, examples of why this is necessary are found in an experiment with kittens that don't develop normal vision because they are carried around in a gondola instead of being able to move themselves. And the prism goggles that switch left and right and that people completely adapt to that after a short period of something like 2 weeks.

Your brain collects up all the information from the senses before it decides upon a story of what happens.

Brains integrate sensory information, but sensory information is gathered at a different speed depending from which sense it comes. Vision takes longer than audio for example. The brain nonetheless coherently fuses together all of these inputs from the same moment, after they have all occurred and are all processed into our coherent picture of reality. But that's also why there is an inevitable delay between the reality we can experience and what is happening in the real world.

To synchronize the incoming information from the senses, the cost is that our conscious awareness lags behind the physical world.

Brain function cannot be understood as the sum of activity in a collection of well defined modules.

Brains imagine their reality and try to predict what the sensory stimulus are going to be like. Therefore even in the absence of sensual stimuli people can see and hear things. Things that come from random chatter formed into coherent pictures and sounds and so on by past experiences. That's probably also the basis for imagination.

At any moment, what we experience as seeing relies less on the light streaming into our eyes, and more on what's already inside our heads.

Remove the world and the show still goes on.

People don't take the world in its full details, even though the mental picture might seem complete, it isn't. One of the reason is saccades during which we are completely blind. While our eyes fixate on a new point they don't see what's going on anymore.

In many cases, the eyes are pointed in the right direction, but the brain isn't seeing what's out there.

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

We only perceive a small sliver of what is out there. And our perceptions are not like reality anyways. Reality is without perception, just molecules floating around emitting certain wavelengths photons, what our brains make of it is highly individual. So my experience is probably different fr yours and what it means for me to see "red" is different from what it means to you. A place where that becomes self evident is people with synesthesia, where those people start mixing and associating sensory perceptions in ways that are out of the ordinary. People smelling colors, tasting words, seeing sounds, and so on are some of the best evidence of the subjectivity of the reality we experience and how it is connected to the exact wiring of our brains.

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

When things are life-threateningly scary, it's a good time to take notes.

Brains perception of time is not fixed, during situations of stress it can feel like it stretches, because the amount of new memories formed is higher during those periods. The amygdala sensing danger puts the brain into attentive mode, paying attention so that the next time around we have more data to handle the dangerous situation well. The unusually high density of new memories during those times leads to the bias in hindsight of how long the time felt.

Your brain serves up a narrative - and each of us believes whatever narrative it tells.

It's morning. The streets of your neighborhood are quiet as the sun peeks above the horizon. In bedrooms all over your city, one by one, an astonishing event is taking place: human consciousness is flickering to life. The most complex object on our planet is becoming aware that it exists.

The question who is steering the ship of the brain comes up. Many many things happen underneath the threshold of conscious awareness. Vast amounts of computations that have to happen for the simplest and mundanest of task to be executed properly. When looked at closely those small feats, don't seem that easy anymore and a world of complex calculations and microadjustments of muscles comes into view. For us to grab a cup of coffee and drink a small sip the amount of computation required is mindboggling, and hence it is something robotics still struggles with to replicate and match in accuracy and performance. And our hands and minds can do so much more, catching balls mid flight, running, parkour, play the violin, and all of that while there is still more activity even more hidden away from view. Things like controlling the internals of our bodies, our breathing, our digestion and feelings of hunger, cold, regulation of blood pressure etc. And the crazy part is, we don't ever have the feeling of doing any of this work, all of this happens in the background, without us noticing any of it. The author thinks that's crazy and I agree.

Yet I have no perception of this lightning storm in my brain. Although my neural networks are screaming with activity, my conscious awareness experiences something quite different. Something more like total obliviousness.

The brain can run things on autopilot after having been exposed to a stimulus and behavior often enough, when this happens we lose conscious access to the thing we do, but we do it effortlessly and with perfection. In a way that is the ultimate goal of practice, to make awareness obsolete and the brain automate the behavior, by building in dedicated circuitry to support that specific behavior.

Consciousness is not even involved in decisions and coming up of thoughts all that often. The vast depths of the unconscious are by definition mostly hidden from view, we can not being them to awareness, yet they play a role in everything we do. We constantly notice things and act on them, even if we don't know that those things were there in the first place, we notice and are influenced and nudged, but never become aware of it. Examples include strippers getting more cash while they are ovulating, people marrying people that have the same starting letter, men being attracted to people who's pupils are dilated etc.

Most of the time you are not aware of the decisions being made on your behalf.

Consciousness evolved to deal with conflicts inside of the brain, to make decisions on conflicting inputs that are best for long-term survival of the organism. It is also useful to adapt to things that are completely new and very unexpected. When something is surprising we pay attention and can use that to learn why and how exactly it was surprising and update our view of the world to eventually sink back into normal autopilot mode, without any conscious awareness of it. Only if there is this element of misprediction or internal conflict do we become conscious of our actions and what we are doing. Other than that we are zombies on autopilot.

A CEO is a company's most abstract view of itself.

In terms of the brain, consciousness is a way for billions of cells to see themselves as a unified whole, a way for a complex system to hold up a mirror to itself.

The question of free will comes up. If a choice is the output of the complex web of neurons interacting with one another and the environment, formed over a lifetime, that leads to us moving on this or that way, where does free will enter the picture? It get's even more confusing when considering that there are experiments that can predictably change a decision one is about to make, yet one feels like the decision was their all along. Maybe free will then, is an illusion? Maybe actions are determined, but the sheer complexity of brains, doesn't allow prediction, similar to other situations like fluid dynamics, where we even have complete equations and much simpler systems, that are essentially deterministic, yet we can't predict even basic facts of them or how they will look like in the future. It's the same for brains, especially if one considers the huge environment and how it affects the brain and the brain affects the environment back.

The conscious mind excels at telling itself the narrative of being in control.

Across the space of a dinner table, or the length of a lecture hall, or the reach of the internet, all the human neurons on the planet are influencing on other, creating a system of unimaginable complexity.

Your brain is like a neural parliament, composed of rival political parties, which fight it out to steer the ship of the state.

Neurons make electrical signals that can be measured by electrodes. This signals can then be converted into sounds, making noises, pop!, pop!, pop!... Whenever a neuron fires, one can listen in on those activities of the brain and be awed, that everything humans ever did, sounded like those decisions being made.

Making choices is tied to bodily feelings, the brain simulates what it would feel like when the decision would have been made and then uses the bodily feedback it gets as a summary of information to decide whether or not to pursue the thing in question. In people who have lost that bodily emotional feedback, decision making is heavily impaired. They can reason through pros and cons endlessly without ever being able to decide and do something. They are stuck without being able to decide.

Political persuasion emerges at the intersection of the mental and the corporal.

Sharks don't go on hunger strikes. - Read Montague.

Only humans regularly override their basic needs in deference to abstract ideals.

When faced with decisions the brain can simulate what it's representation of the world is going to be after the decision and associated motor actions has been done. This can be used to decide, since it can evaluate those resulting mental states for their anticipated reward and choose the one that has the best outlook. But the brain can learn from what happens after we do an action. It can observe the actual state reality is in after it and compare it to what it expected and then update the mappings accordingly. The brain is essentially a self updating prediction machine, learning continuously how the world works and how to operate in it effectively, so that it's host (you) can survive and reproduce nicely. That's what it has been programmed to do, by its genes and what its built in structure dictates. We have the value function built in, but can figure out the details of action on our. The areas involved in the updating and tracking of value functions are the ventral tegmental areas and the substantia nigra (among others)

Time traveling is something the human brain does relentlessly.

Your valuation of everything around you is changeable, because quite often your predictions don't match what happens.

There's a twist that often gets in the way of good decision making: options right in front of us tend to be valued higher than those we merely simulate.

Idea of an Ulysses contract, where the future person would like to decide differently but we don't let that happen, because we anticipated it and prepared precautions against it. This way we can correct for the bias we have for short term options and force us to do long-term decisions, without crashing on the shorelines of the siren's islands.

To make better decisions it's not only important to know yourself, but all your selves.

Drugs effectively tell the brain that this decision is better than all the other things one could be doing.

Without the ability to weigh alternatives, we would be hostages to our most basic drives.

Addiction is a permanent strengthening of the networks weighing short term benefits over long-term benefits. Therefore people in addiction kind of have a deck of cards that is heavily stacked against their favor. Whenever they are confronted with making a decision their short term networks overpower the long-term thinking ones and lead to the bad outcome of the decision. A new approach the David Eaglemans team tries for curing that is giving addicts insights into how their brains and those two networks perform with brain scanning techniques. To make that fight over what they are going to do visible, so that they can develop better strategies to deal with craving and their addiction.

Our neurons require other people's neurons to thrive and survive.

Humans are social animals, in a way one can think of all brains as connected, influencing each other permanently via ideas and culture. The whole brains of humanity form a mind of super organism, evolving ever faster with the rise of technology and better spreading of information to influence other brains. But humans are also very social, we detect what others feel and want, and act accordingly. Those circuits form very early and are very deeply integrated into how our brains work. We detect agency and stories and social/unsocial behavior in almost everything, even simple shapes can be imbued with narrative and small babies can already judge whether certain agents are helpful or not based on interactions they have seen them perform in the past and that guides their decision making already.

Every moment of our lives our brain circuitry decodes the emotional of others based on extremely subtle facial cues.

Humans mirror other humans faces to decipher how they feel. By knowing how we feel when we make their face we can guess at how they feel. People with Botox injections lose parts of that ability because their facial muscles are unable to move because of the injected neurotoxin.

We can feel the pain of others, just like it were our pain, because we use the same circuitry to process both, it is similar for other emotions, without social contact and context the brain atrophies and it leaves emotional scars. Interestingly being left out and other social problems lead to the same pain areas being activated that are active when we feel physical pain.

To empathize with another person is to feel their pain.

How can people kill so many, even though we can also cooperate so greatly with one another? The answer lies in the neurons, as with everything else as well. Namely that the emotional parts of the brain become suppressed when acting towards people that we consider not to be in our group. Therefore those people, even though human, are not evaluated as such by our brains and enable humans to do all the cruel things they do to each other. It's because of categorization of people as "like me" or "not like me" and those categories can be arbitrary (religion, skin color, nationality, whatever). People in the wrong category are not seen as people by the brain at all. And therefore every behavior that is permissible towards objects are permissible to those people. This is also known as dehumanization.

A basic categorization is enough to change your brain's pre-conscious response to another person in pain.

An experiment in a school, teacher says, blue eyed people are better, just by this categorization, suddenly friends start to be mean to their friends etc. some arbitrary rule made up by a teacher out of thin air is enough to change behavior and lead to this ingroup/outgroup madness. The paradigm shift for the children comes when the next day the rules are reversed.

Your neurons and those of everyone on the planet interplay in a giant, shifting super-organism. What we demarcate as you is simply a network in a larger network. If we want a bright future for our species, well want to continue to research how human brains interact - the dangers as well as the opportunities. Because there's no avoiding the truth etched into the wiring of our brains: we need each other.

We're at a moment in human history when the marriage of our biology and our technology will transcend the brain's limitations.

Brains are hyper plastic, even with just one half of the brain, early on removing the other half by surgery, people can grow up to be normal functioning adults. This plasticity is also used to adapt the brain to different forms of sensory data, such as the data provided from implants. The brain is just good at picking out patterns in data, and building a model of reality from it, even if the data doesn't come from the original senses and in a different format etc. from a video camera. The brain learns to use the information.

We've gone from living as primitive hunter gatherers surviving on scraps to a planet conquering hyper-connectrd species that defines its own destiny.

Whatever information comes in, the brain figures out what to do with it.

The crucible of natural selection is the ultimate hacker space.

There may be nothing special or fundamental about the sensors we're used to. They're just what we've inherited from a complex history of evolutionary constraints. We're not stuck with them!

It's crazy if you think about the implications of those few pages. The way our reality is constructed is not in the hands of evolution anymore, but in our, brains can learn to interface with whatever data we give them and make sense of it. "Senses" in the way we use to think of them can be used to feed different data directly. Why make it hard to "read" a book, if you could simply "feel" it? One question remains though and that is that of speed and attention necessary for these mechanisms. Probably feeling data is not much better than seeing it so why not just see it in the first place? Maybe the compression/intuitive understanding of making sense of data and it's regularities which our brain does on sensory data anyways could be used to gain deeper insight into reality? Such that Trends and mathematical functions etc. become very much intuitive, the way it is intuitive to catch a ball? Also think of the kind of artistic mediums this kind of technology would enable! Art would be freaking crazy since it then comes to its most natural form, patterns of data that when experienced create certain states of consciousness. That would be properly insane.

What if you could have real time data streamed into your body, so that it became part of your direct experience of the world? In other words, what if you could feel data?

We will wire ourselves into an expanded sensory reality.

If you also couple the output of the brain to different actuators, holy shit what would it mean? People could quite be spaceships, controlling thrust and feeling whatever the sensory data from them, the space ship makes them feel. That's a trippy thought...

What if you could use your brain signals to wirelessly control a machine across the room?

The body we arrive with is just the starting point for humanity. In the distant future, we won't just be extending our physical bodies, but fundamentally our sense of self.

Idea of preserving the body or brain structure by freezing it, a gamble on future technologies being good enough to revive the people, that were frozen today, so they can have a second chance at life. Another way to go about this would be to save all the data of a brain that makes a person this specific person and then run a simulation of that data on inputs or transfer it into a kind of "mechanical" brain contained within a new body. Problem with this is the sheer amount of data necessary to build such a thing. Even crazier when one factors in not only the connections, but the actual chemical character of individual synapses etc. since those chemical details make up a lot of the learning and experiences as well. And even then the critical question remains - would that be you? Would that vastly complex simulation even be conscious?

Ther will come a moment when all your neural activity will come to a halt and then the glorious experience of being conscious will come to an end. It doesn't matter who you know or what you do: this is the fate of all of us. In fact, it's the fate of all life, but only humans are so unusually foresighted that we suffer over this knowledge.

The typical brain has about eighty-six billion neurons, each making about ten thousand connections. They connect in a very specific manner, unique to each person. Your experiences, your memories, all the stuff that makes you you is represented by the unique pattern of the quadrillion connections between your brain cells. This pattern, far too large to comprehend, is summarized as your "connectome".198-199

Eagleman poses the question if a machine could be sentient or whether there is something special about the wet ware our brains use. He introduces the Chinese Room experiment and the Computational Hypothesis. In a way he asks the question if the brain and what makes consciousness is only in the connectome and the chemical details of the material thing and can therefore be simulated or whether there is something outside of that material reality that gives brains consciousness... In the end, we don't know yet.

Can a Computer ever be programmed so that it has awareness, a mind?

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?

The last bit of the book deals with emergence and how it can pose an answer to the riddle of consciousness in the brain and an intriguing answer to the Chinese Room experiment. In a way the human brain is like an ant colony, each neuron doesn't know what it is doing in the large context yet by following it's local set of rules and chemistry contributes to this larger whole and the emergent property of a mind emerges from those local rules, without the understanding of the single neuron being involved. In an ant colony it's just the same, their complex civilization comes about by simple rules as well.

Each ant doesn't know that it is part of a successful civilization: it just runs its small, simple programs.

A neuron is simply a Specialized cell, just like other cells in your body, but with some specializations that low it to grow processed and propagated electrical signals. Like an ant, an individual brain cell just runs its local program its whole life, carrying electrical signals along its membrane, spitting out neurotransmitters when the time comes for it, and being spat upon by the neurotransmitters of other cells. That's it. It lives in darkness.

Although your goals, intentions, and abilities are completely dependent on the existence of these little neurons, they live on a smaller scale, with no awareness of the thing they have come together to build.

He brings up another example of emergent properties, that of flight of hunks of metal strung together in the right way called an airplane, this begs the question then - do we understand emergence at all? Is there a scientific theory around it as to when and how it arises, that connects anthills, airplanes and brains? I think the answer is no, and we do a lot of handwaving to cover it up at that point. Eagleman makes a connection similar to this and asks - if a brain is just an emergent property of many single things acting together in a complex way, then could a city or the internet or an anthill for that matter, be conscious? Maybe the answer is no, since it is about connectedness. In conscious states the brain is vastly more connected than a city will ever be. A flicker of neural activity from a TMS probe spreads through a huge chunk of brain. Maybe that is the defining character of consciousness then. If information flows through a system the right way, far enough, then it can be assumed to be conscious.

Only one thing is certain: Our species is just at the beginning of something, and we don't fully know what it is.

Who we become, is up to us.