Speaker 1: In this episode.
Speaker 2: In the next one, I want to dive into a
Speaker 2: fundamental philosophical question, probably the most important one that we
Speaker 2: have as humans, which is what it means to know ourselves?
Speaker 2: In other words, as people living in the twenty first century,
Speaker 2: with all of this massive biological data and the insights,
Speaker 2: what does that tell us about the ancient question of
Speaker 2: who we are? Do we have something like souls? Are
Speaker 2: we just a bunch of neurons? Are there other ways
Speaker 2: to look at this? There's a sense in which I'm
Speaker 2: constantly surprised that this question who am I? Isn't talked
Speaker 2: about all the time. I mean, most people spend most
Speaker 2: of their time talking about sports teams or the latest celebrity,
Speaker 2: or traffic or whatever food they like or whatever.
Speaker 1: But we find ourselves.
Speaker 2: Here in this mysterious existence where you don't really remember
Speaker 2: getting here, and you're told that one day you'll disappear
Speaker 2: from here. And it surprises me that this isn't what
Speaker 2: we're talking about all the time. Why isn't this what
Speaker 2: we're using the internet to discuss. Why don't we have
Speaker 2: world leaders coming together not for the United Nations Annual Meeting,
Speaker 2: but to dig their teeth into this question and bring
Speaker 2: evidence to bear on different hypotheses. Why isn't this the
Speaker 2: topic of conversation on every single news program? So for
Speaker 2: the next two episodes, we're going to dig in and
Speaker 2: I always start with some questions to give you a
Speaker 2: sense of the weirdness of the roadmap.
Speaker 1: So here we go.
Speaker 2: Would you appreciate Taylor Swift if you only had an
Speaker 2: internal camera to watch her vocal cords jumping around? What
Speaker 2: do almost all drugs of abuse have in common? How
Speaker 2: can the tiny molecules of the rabies virus control your behavior?
Speaker 2: Did Joan of arc turn the tide of the one
Speaker 2: hundred Years War as the result of a brain disorder?
Speaker 2: And what does any of this have to do with
Speaker 2: who you are? And the question of your essence as
Speaker 2: a person, the essence that your friends know and love
Speaker 2: as you?
Speaker 1: Where does that come from? Welcome to Inner.
Speaker 2: Cosmos with me David Eagleman. I'm a neuroscientist and an
Speaker 2: author at Stanford and in the next couple of episodes,
Speaker 2: we're going to sail deeply into our three pound universe
Speaker 2: to dig in to one of the most fundamental questions
Speaker 2: of our experience in the world. Now I've talked about
Speaker 2: this fact before, but I need to emphasize for this
Speaker 2: episode that the brain is the most complex structure we
Speaker 2: have ever discovered in our universe. It's got almost one
Speaker 2: hundred billion neurons and hundreds of trillions of connections. Now,
Speaker 2: this kind of complexity is simply not understandable by a
Speaker 2: human mind. And yet we know that somehow your brain
Speaker 2: is you. All of your hopes and dreams and aspirations,
Speaker 2: the agony, the ecstasy, it's all contained in that three
Speaker 2: pound organ in your skull. Now how do we know
Speaker 2: that because every day in clinics all over the world,
Speaker 2: we see people with damage to their brains, even very
Speaker 2: tiny damage, and that changes who they are. Small bits
Speaker 2: of damage caused by a stroke or a traumatic brain injury,
Speaker 2: or a tumor or whatever. These can change your decision
Speaker 2: making or your ability to see colors, or understand music
Speaker 2: or name animals. It can make you more or less
Speaker 2: prone to gambling, or more talkative or less talkative. It
Speaker 2: can make you not know the names of objects or
Speaker 2: not know how to interact with objects anymore, or make
Speaker 2: you unable to speak or to understand speech, or one
Speaker 2: hundred other things. And this is how we came to
Speaker 2: have this strange hypothesis that you are your brain. So
Speaker 2: to start this question of who are we, let's step
Speaker 2: back a little bit. In history, people have always been
Speaker 2: wondering who we are, mostly because our existence is so
Speaker 2: deeply weird, and traditionally the answer has been about deities
Speaker 2: and immortal souls, but not everyone has been willing to
Speaker 2: stop there. So I was impressed some years ago when
Speaker 2: I read about the French essayist Montaigne, who in fifteen
Speaker 2: seventy one, on the morning of his thirty eighth birthday,
Speaker 2: decided to make a radical change in his life's trajectory.
Speaker 2: He quit his career in public life, and he set
Speaker 2: up a library with one thousand books in a tower
Speaker 2: at the back of his large estate, and he spent
Speaker 2: the rest of his life writing essays about the subject
Speaker 2: that interested him the most, the search for oneself. His
Speaker 2: first conclusion was that the search to no one's self
Speaker 2: is a fool's errand because the self who I am,
Speaker 2: is always changing and staying a few steps ahead of
Speaker 2: a firm description. But that didn't stop him from searching,
Speaker 2: and his question has resonated through the centuries.
Speaker 1: Causasia, what do. I know.
Speaker 2: That was a good question, and it remains so because
Speaker 2: when we dive in to explore the inner cosmos, as
Speaker 2: we've been doing on this podcast, we can't help find
Speaker 2: ourselves disabused of our initial notions that knowing ourselves will
Speaker 2: be uncomplicated and intuitive, because we see that self knowledge
Speaker 2: requires as much work from the outside in the form
Speaker 2: of science as from the inside introspection.
Speaker 1: And this is not to.
Speaker 2: Say that we can't grow better at introspection. After all,
Speaker 2: we can learn how to pay attention to what we're
Speaker 2: really seeing out there, like painters do, and we can
Speaker 2: attend more closely to our internal signals like Yogi's do.
Speaker 2: But there are limits to introspection. Just consider the fact
Speaker 2: that your peripheral nervous system employs one hundred million neurons
Speaker 2: to control the activities in your gut. This is called
Speaker 2: the enteric nervous system one hundred million neurons, and no
Speaker 2: amount of your introspection can touch this, nor by the way,
Speaker 2: would you want it to be. In The tek nervous
Speaker 2: system is better off running as the automated optimized machinery
Speaker 2: that it is, routing food along your gut and providing
Speaker 2: chemical signals to control the digestion factory without asking your
Speaker 2: opinion on the matter. Now, this has always fascinated me
Speaker 2: to think that in some cases there may be not
Speaker 2: only a lack of access, but even an active prevention
Speaker 2: of access. For example, I was once chewing on this
Speaker 2: with my thesis advisor, Read Montague, and he speculated that
Speaker 2: we might have algorithms that protect us from ourselves. This
Speaker 2: is analogous to your laptop computer, which has a boot
Speaker 2: sector that's inaccessible by the operating system, because the boot
Speaker 2: sector is too important for the operation of the computer
Speaker 2: for any high level systems to find inroads and gain
Speaker 2: admission under any circumstances.
Speaker 1: So Read noted.
Speaker 2: That whenever we try to think about ourselves too much,
Speaker 2: we tend to blink out, and the analogy was that
Speaker 2: we're getting too close to the boot sector. Now, he
Speaker 2: was just speculating here, but the idea is fascinating that
Speaker 2: maybe our system has evolved to make certain that we
Speaker 2: can't access the details too deeply. Or, as Ralph Waldo
Speaker 2: Emerson put the same idea from a more poetic point
Speaker 2: of view, everything intercepts us from ourselves. So whether it's
Speaker 2: just a lack of access or an active prevention of access.
Speaker 2: The bottom line is that much of who we are
Speaker 2: remains outside of our conscious control, or our opinion or
Speaker 2: our choice. We talked in an earlier episode about the
Speaker 2: impossibility of changing your sense of beauty or attraction. What
Speaker 2: would happen if someone commanded you to be attracted to
Speaker 2: someone that you're not, or to be attracted to a
Speaker 2: gender that you're not attracted to, or to an animal
Speaker 2: outside your species.
Speaker 1: Could you muster attraction there? Doubtful.
Speaker 2: Your most fundamental drives are stitched into the fabric of
Speaker 2: your neural circuitry, and they are inaccessible to you. You
Speaker 2: can't reach in there and change them around. You find
Speaker 2: certain things more attractive than others, and you don't know why. So,
Speaker 2: like your nervous system in your gut and your sense
Speaker 2: of attraction, almost the entirety of your inner universe is
Speaker 2: foreign to you. Consider when an idea strikes you, you
Speaker 2: don't know where the heck that came from. One minute
Speaker 2: you didn't have it, and the next moment it's there.
Speaker 2: It just appears even though it came from your brain,
Speaker 2: it may as well have been handed to you from
Speaker 2: somewhere else. You don't know the neuronal history of the idea,
Speaker 2: and you don't care. You just think, oh, that's a
Speaker 2: good idea. And this is the same with your train
Speaker 2: of thought during a day dream, or the bizarre content
Speaker 2: of your nighttime dreams. All these are just served up
Speaker 2: to you from unseen intracranial caverns. So what does all
Speaker 2: of this mean for the Greek admonition to know thyself?
Speaker 2: These were the words inscribed in the Temple of Apollo
Speaker 2: at Delphi, know thyself? Can we ever know ourselves more
Speaker 2: deeply by studying our neurobiology? And I'm going to argue yes,
Speaker 2: but with some interesting nuances, And I'll give you an
Speaker 2: analogy here to physics. In the face of the deep
Speaker 2: mysteries presented by quantum physics, the physicist Neils Brer suggested
Speaker 2: that an understanding of the structure of the atom could
Speaker 2: be accomplished only by changing the definition of to understand,
Speaker 2: because with quantum mechanics you couldn't any longer draw pictures
Speaker 2: of an atom, so that was lost. But instead one
Speaker 2: could now predict experiments about an atom's behavior out to
Speaker 2: fourteen decimal places, So lost assumptions were replaced by something richer.
Speaker 2: And by the same token, to know one's self may
Speaker 2: require a change of definition of to know. Knowing yourself
Speaker 2: now requires the understanding that the conscious you occupies only
Speaker 2: a small room in the mansion of the brain, and
Speaker 2: that it has very little control over the reality that
Speaker 2: gets constructed for you. So the invocation to know thyself
Speaker 2: needs to be considered in new ways because when we
Speaker 2: look at the trillions of neurons and there are sex
Speaker 2: tillions of proteins and biochemicals, what does it mean to
Speaker 2: know ourselves from that totally unfamiliar perspective, As we're going
Speaker 2: to see, we need the neurobiological data and we also
Speaker 2: need quite a bit more to know ourselves. Why because
Speaker 2: the biological data is fundamental, but it has its limitations.
Speaker 2: Imagine that you got Taylor Swift to come to your
Speaker 2: house and sing for you, but instead of listening to her,
Speaker 2: you put on ear muffs and you lower a medical
Speaker 2: scope down her throat and you get.
Speaker 1: A good close up view of her vocal chords.
Speaker 2: They're slimy and shiny, and they're contracting in and out
Speaker 2: and spasms. Now, you could watch this and study the
Speaker 2: details all day, but it wouldn't get you any closer
Speaker 2: to understanding why her songs are big hits, or what
Speaker 2: the words mean to you, or how they make you feel.
Speaker 2: By itself, in its raw form, the biology is only
Speaker 2: going to give you partial insight there. It's the best
Speaker 2: that we can do for now, but it's far from complete.
Speaker 2: So this is what we're going to talk about today.
Speaker 2: What does and doesn't it mean to be constructed out
Speaker 2: of physical parts. So let's start with a clear and
Speaker 2: famous example of brain damage. I've mentioned this story in
Speaker 2: a previous episode, but i'll retell it here with more detail.
Speaker 2: In eighteen forty eight, there was a work gang foreman
Speaker 2: twenty five years old. His name was Phineas Gage. On
Speaker 2: September twenty first of that year, the Boston Post wrote
Speaker 2: a short article under the headline horrible accident. Here's how
Speaker 2: it went. Quote as Phineas P. Gage, a foreman on
Speaker 2: the railroad in Cavendish, was yesterday engaged in tamping.
Speaker 1: For a blast.
Speaker 2: The powder exploded, carrying an instrument and threw his head
Speaker 2: an inch and a fourth in diameter and three feet
Speaker 2: and seven inches in length, which he was using at
Speaker 2: the time. The iron entered on the side of his face,
Speaker 2: shattering the upper jaw and passing back of the left
Speaker 2: eye and out at the top of the head.
Speaker 1: So this was an iron tamping rod, and.
Speaker 2: Because of an explosion of gunpowder, this blew through his
Speaker 2: head and it clattered to the ground twenty five yards away. Now,
Speaker 2: while Phineas Gage wasn't the first person to have his
Speaker 2: skull punctured and a portion of his brain spirited away
Speaker 2: by a projectile, he was the first, so far as
Speaker 2: we know, to not die from it. And in fact,
Speaker 2: Gauge didn't even lose consciousness. So the first physician to
Speaker 2: arrive at the scene, a doctor Williams, didn't believe Gauge's
Speaker 2: statements of what had just happened, but instead he quote
Speaker 2: thought that he Gauge was this. But doctor Williams soon
Speaker 2: understood the gravity of what had happened when quote mister
Speaker 2: Gage got up and vomited, and the effort of vomiting
Speaker 2: pressed out about half a tea cupful of brain, which
Speaker 2: fell upon the floor end quote. The Harvard surgeon who
Speaker 2: studied his case noted that quote, the leading feature of
Speaker 2: this case is its improbability. It is unparalleled in the
Speaker 2: annals of surgery.
Speaker 1: End quote.
Speaker 2: The Boston Post article summarized this improbability with just one
Speaker 2: more sentence. Quote, The most singular circumstance connected with this
Speaker 2: melancholy affair is that he was alive at two o'clock
Speaker 2: this afternoon and in full possession of his reason and
Speaker 2: free from pain unquote. Now Gage's survival alone would have
Speaker 2: made this an interesting medical case, it became a famous
Speaker 2: case because of some thing else that came to light.
Speaker 2: Two months after the accident, his physician reported that Gage
Speaker 2: was quote feeling better in every respect walking about the
Speaker 2: house again, says he feels no pain in the head unquote,
Speaker 2: but foreshadowing a larger problem. The doctor also noted that
Speaker 2: Gauge quote appears to be in a way of recovering
Speaker 2: if he can be controlled end quote. So what did
Speaker 2: he mean here, if he can be controlled? It turned
Speaker 2: out that the pre accident, Phineas Gage had been described
Speaker 2: as a great favorite among his team, and his employers
Speaker 2: had hailed him as the most efficient and capable foreman
Speaker 2: in their employ But after the brain damage, his employers
Speaker 2: considered him to be such a different person that they
Speaker 2: decided they couldn't give him his place again. Now, what
Speaker 2: was this change in his personality. Here's what Gauge's Physics
Speaker 2: wrote twenty years later in eighteen sixty eight. This is
Speaker 2: a long quotation, but I'm going to read the whole
Speaker 2: thing because it's fascinating and gives us insight into how
Speaker 2: a person can change when his brain changes.
Speaker 1: Quote.
Speaker 2: The equilibrium or balance, so to speak, between his intellectual
Speaker 2: faculties and animal propensities seems to have been destroyed. He
Speaker 2: is fitful, irreverent, indulging at times in the grossest profanity,
Speaker 2: which was not previously his custom manifesting, but little deference
Speaker 2: for his fellows, impatient of restraint or advice when it
Speaker 2: conflicts with his desires, at times pertinaciously obstinate, yet capricious
Speaker 2: and vacillating, devising many plans of future operations which are
Speaker 2: no sooner arranged than they are abandoned in turn for others,
Speaker 2: Appearing more feasible a child in his intellectual capacity and
Speaker 2: manner infestations. He has the animal passions of a strong
Speaker 2: man previous to his injury. Although untrained in the schools,
Speaker 2: he possessed a well balanced mind and was looked upon
Speaker 2: by those who knew him as a shrewd, smart businessman.
Speaker 2: Very energetic and persistent in executing all his plans of operation.
Speaker 2: In this regard, his mind was radically changed, so decidedly
Speaker 2: that his friends and acquaintances said he was quote no
Speaker 2: longer gauge end quote. Now in the intervening century in half,
Speaker 2: we've seen lots of cases like Phineas Gages, because tragically,
Speaker 2: there are lots of ways for the delicate pink material
Speaker 2: of the brain to get hurt, and they all surface
Speaker 2: the same lesson. When the brain changes, the person changes.
Speaker 2: And of course the more common thing seen in hospitals
Speaker 2: every day are all of nature's tragic experiments strokes, tumors, neurodegeneration,
Speaker 2: And it's the same lesson. The condition of your brain
Speaker 2: is central to who you are. You that all your
Speaker 2: friends know and love cannot exist unless all the fine
Speaker 2: microscopic details of your brain, all the nuts and bolts,
Speaker 2: are in place. If you don't believe me, step into
Speaker 2: any neurology ward in any hospital. Damaged to even small
Speaker 2: parts of the brain can lead to the loss of
Speaker 2: shockingly specific abilities, the ability to understand music, or to
Speaker 2: manage risky behavior, or to distinguish colors, or to arbitrate
Speaker 2: simple decisions. We see examples of this when we meet
Speaker 2: patients who lose the ability to see movement even though
Speaker 2: they're not blind. We see it when a person gets
Speaker 2: front do temporal dementia and starts shoplifting, even though that's
Speaker 2: something they would have never done before. We see it
Speaker 2: when a person no longer understand how a mirror reflection works.
Speaker 2: We see it when medications for Parkinson's disease turn someone
Speaker 2: into a compulsive gambler, or a million other examples that
Speaker 2: tell us that your essence can be changed by changes
Speaker 2: in your brain. So all of this leads to a
Speaker 2: key question. Do we possess a soul that is separate
Speaker 2: from our physical biology? Or are we simply an enormously
Speaker 2: complex biological network that mechanically produces our hopes and aspirations
Speaker 2: and dreams and desires and humor and passion. So over
Speaker 2: this and the next episode, this is the question I'm
Speaker 2: going to unpack. Now, the majority of people on the
Speaker 2: planet vote for the extra biological soul, but all the
Speaker 2: evidence from neuroscience suggests it's the biology. It's a vast
Speaker 2: physical system from which the essence of a person emerges,
Speaker 2: and nothing more than that. Now, do we know which
Speaker 2: answer is correct, not with certainty, but cases like Phineas
Speaker 2: Gauges and every case of brain damage we see in
Speaker 2: the hospitals certainly seem to weigh in on the problem.
Speaker 2: They make it more and more difficult to ignore or
Speaker 2: deny that we are biological creatures. So the materialist viewpoint
Speaker 2: holds that we are fundamentally made only of physical materials.
Speaker 2: In this view, the brain is a system whose operation
Speaker 2: is governed by the laws of chemistry and physics, with
Speaker 2: the end result that all of your thoughts and emotions
Speaker 2: and decisions are produced by natural reactions following local laws
Speaker 2: to lowest potential energy. We are our brain and its chemicals,
Speaker 2: and any dialing of the knobs of your neural system
Speaker 2: changes who you are now. A common approach to materialism
Speaker 2: is called reductionism, and this theory puts forth the hope
Speaker 2: that we can successively reduce the problems down to their
Speaker 2: small scale biological pieces and parts, and eventually come to
Speaker 2: explain complex phenomena like happiness or greed, or narcissism or
Speaker 2: compassion or malice or caution or amazement by understanding the
Speaker 2: pieces and parts at first blush the materialist and reductionist
Speaker 2: viewpoints sound absurd to a lot of people. Not to
Speaker 2: everyone I work with, and possibly not to a lot
Speaker 2: of the listeners of this podcast, but probably to many
Speaker 2: of the people on this planet. And I know this
Speaker 2: in part because when I sit next to strangers on
Speaker 2: a plane or a subway, I ask their opinions about
Speaker 2: this kind of stuff, and people will often say something like, look,
Speaker 2: why I chose my job, how I fell in love
Speaker 2: with my wife, what TV shows I like to watch?
Speaker 2: That has nothing to do with the cells of my brain.
Speaker 2: That's just who I am. And they're right to think
Speaker 2: that the connection between your essence as a person and
Speaker 2: a squishy confederacy of cells that seems distant at best,
Speaker 2: that person's decisions came from them, not from a bunch
Speaker 2: of chemicals cascading through invisibly small cycles.
Speaker 1: Right.
Speaker 2: But what happens when we run into enough cases like
Speaker 2: Phineas Gauges or people who have strokes or tumors or neurodegeneration,
Speaker 2: And what happens when we turn the spotlight on even
Speaker 2: more subtle influences, far more subtle than a tamping rod,
Speaker 2: where changes in the brain change people's personalities. Just consider
Speaker 2: this as an example, Think about the powerful effects of
Speaker 2: the small molecules that we call narcotics. These are invisibly small,
Speaker 2: but they alter consciousness, they affect cognition, they navigate behavior.
Speaker 2: We are slave to these molecules tobacco, alcohol, and cocaine.
Speaker 2: These are self administered universally for the purpose of mood changing.
Speaker 2: And if we knew nothing else about neurobiology, the mere
Speaker 2: existence of narcotics would give us all the evidence we
Speaker 2: need to tell us that our behavior and psychology can
Speaker 2: be commandeered at the molecular level. Take cocaine as an example.
Speaker 2: Cocaine interacts with a very specific network in the brain,
Speaker 2: one that registers rewarding events. This is known as the
Speaker 2: mesolimbic dopamine system. It registers rewarding events like you satisfying
Speaker 2: your thirst with a a cool iced tea, or winning
Speaker 2: a smile from the right person, or cracking a tough
Speaker 2: problem at work and your boss says good job. By
Speaker 2: tying positive outcomes to the behaviors that led to them,
Speaker 2: this neural circuit learns how to optimize behavior in the world.
Speaker 2: It's what helps us get food and drink and mates
Speaker 2: and navigate life's daily decisions now out of context. Cocaine
Speaker 2: is a totally uninteresting molecule. It has seventeen carbon atoms
Speaker 2: and twenty one hydrogens and one nitrogen and four oxygens.
Speaker 2: What makes cocaine cocaine is the fact that its shape
Speaker 2: happens to fit lock and key into the microscopic machinery
Speaker 2: of this reward circuit. So suddenly the cocaine gets to
Speaker 2: act like the most rewarding thing you've done, which causes you,
Speaker 2: in the language of the reward system, to want to
Speaker 2: do that again. And by the way, the same thing
Speaker 2: goes for all four major classes of drugs of abuse, alcohol, nicotine,
Speaker 2: psychostimulants like amphetamines, and opiates like morphine. By one inroad
Speaker 2: or another, they all plug into this same reward circuitry.
Speaker 2: All these types of molecules rev the engine of the
Speaker 2: mesolimbic dopamine system, and so they all become self reinforcing.
Speaker 2: Your brain experiences them and then chases.
Speaker 1: More of that.
Speaker 2: And these effects are so powerful that users will end
Speaker 2: up robbing stores and mugging elderly people to continue obtaining
Speaker 2: these specific molecular shapes. And what's really amazing to note
Speaker 2: is that These chemicals work their magic at scales one
Speaker 2: thousand times smaller than the width of a human hair,
Speaker 2: but by attaching in the right spots, they can make
Speaker 2: the consumers feel invincible and euphoric. By plugging into this
Speaker 2: dopamine system, cocaine and its cousins command beer the reward system,
Speaker 2: and they tell the brain that this is the best
Speaker 2: possible thing that could be happening. So these ancient circuits
Speaker 2: that are there for steering our behavior, these become hijacked. Now,
Speaker 2: these cocaine molecules are hundreds of millions of times smaller
Speaker 2: than the tamping rod that shot through Phineas Gage's brain,
Speaker 2: But the lesson is the same. Who you are depends
Speaker 2: on the precise details of your neurobiology, and the dopamine
Speaker 2: system is only one of hundreds of examples. The exact
Speaker 2: levels of other neurotransmitters, for example, serotonin, are critical for
Speaker 2: who you believe yourself to be. If you suffer from
Speaker 2: clinical depression, you'll probably get prescribed a medication known as
Speaker 2: a selective serotonin uptake inhibitor abbreviated as an SSRII, for
Speaker 2: example fluoxetine. Now, everything you need to know about how
Speaker 2: these drugs work is contained in the words uptake inhibitor. Normally,
Speaker 2: channels called transporters take up the serotonin from the space
Speaker 2: between the neurons, and when you inhibit that uptake, you
Speaker 2: get a larger concentration of serotonin in the brain, and
Speaker 2: the increased concentration has direct consequences on cognition and emotion.
Speaker 2: People can go on these medications and they can transition
Speaker 2: from crying on the edge of the bed to standing
Speaker 2: up and showering and getting their job back and rescuing
Speaker 2: healthy relationships with the people in their lives, all because
Speaker 2: of a subtle fine tuning of a neurotransmitter system. If
Speaker 2: this story weren't so common, we would more easily appreciate
Speaker 2: its bizarreness. And it's not just neurotransmitters that influence your cognition.
Speaker 2: The same goes for hormones, the invisibly small molecules that
Speaker 2: surf the bloodstream and cause commotion at every port that
Speaker 2: they visit. If you inject a female rat with estrogen,
Speaker 2: she'll begin seeking a sexual partner. If you inject a
Speaker 2: male rat with testosterone, he'll become aggressive. Actually, in episode fifteen,
Speaker 2: I told you about the wrestler Chris Benoit, who took
Speaker 2: massive doses of testosterone and then murdered his wife and
Speaker 2: his own child in a roid rage. Or just think
Speaker 2: about the hormone fluctuation that accompany normal menstrual cycles. Recently,
Speaker 2: a female friend of mine was at the bottom of
Speaker 2: her menstrual mood changes, and she said to me, you know,
Speaker 2: I'm just not myself for a few days each month.
Speaker 2: But because she's a neuroscientist, she then reflected for just
Speaker 2: a moment. Then she said, or maybe this is the
Speaker 2: real me, and I'm actually someone else the other twenty
Speaker 2: seven days of the month. She wasn't afraid to view
Speaker 2: herself as the sum total of her chemicals at any moment.
Speaker 2: She understood that what we think of as her is
Speaker 2: something like a time averaged version. All these examples add
Speaker 2: up to something of a strange notion of the self.
Speaker 2: Because of inaccessible fluctuations in our biological soup, some days
Speaker 2: we find ourselves more irritable or more humorous, or more
Speaker 2: well spoken, or more calm or energized or clear thinking.
Speaker 2: Our internal life and our external actions are steered by
Speaker 2: these biological cocktails to which we don't have any direct
Speaker 2: access or any direct acquaintance. And don't forget that the
Speaker 2: long list of influences on your mental life. This stretches
Speaker 2: way beyond chemicals. It includes the details of the circuitry
Speaker 2: as well. So consider something like epilepsy. If an epileptic
Speaker 2: seizure is focused in a particular spot in the temporal lobe,
Speaker 2: a person won't have motoric seizures with their body, but
Speaker 2: instead something more subtle. The effect is something like a
Speaker 2: cognitive seizure, and this translates to changes of personality and
Speaker 2: hyper religiosity, which is an obsession with religion, and hypergraphia,
Speaker 2: which is where you write pages and pages on a subject,
Speaker 2: usually about religion, and often the hearing of voe voices
Speaker 2: that get attributed to a god. Some fraction of histories,
Speaker 2: prophets and martyrs and leaders appear to have had temporal
Speaker 2: lobe epilepsy. Consider Joan of Arc, the sixteen year old
Speaker 2: girl who managed to turn the tide of the Hundred Years'
Speaker 2: War because she believed and convinced the French soldiers that
Speaker 2: she was hearing voices from Saint Michael and Saint Catharine,
Speaker 2: and Saint Margaret and Saint Gabriel as she described her experience, quote,
Speaker 2: when I was thirteen, I had a voice from God
Speaker 2: to help me to govern myself. The first time I
Speaker 2: was terrified. The voice came to me about noon. It
Speaker 2: was summer and I was in my father's garden. Later,
Speaker 2: she reported, quote, since God had commanded me to go,
Speaker 2: I must do it. Although it's impossible to retrospectively diagnose
Speaker 2: with certainty what is known about her, including the increasing
Speaker 2: religiosity and ongoing voices. This is consistent with temporal lobe epilepsy.
Speaker 2: When brain activity is kindled in just the right spot,
Speaker 2: people hear voices. If a physician prescribes in anti epileptic medication,
Speaker 2: the electrical spikes go away and the voices disappear. So again,
Speaker 2: our reality depends on what our biology is up to
Speaker 2: and influences on your cognitive life also include tiny non
Speaker 2: human creatures. Microorganisms, like viruses in bacteria, hold sway over
Speaker 2: behavior in extremely specific ways. Here's my favorite example of
Speaker 2: a microscopically small organism taking over the behavior of a
Speaker 2: giant machine, the rabies virus. After a bite from one
Speaker 2: mammal to another, this tiny bullet shaped virus climbs its
Speaker 2: way up the nerves and into the temporal lobe of
Speaker 2: the brain, and there it ingratiates itself into the local
Speaker 2: neurons and it changes the local patterns of activity, and
Speaker 2: by this route it steers the infected host to aggression
Speaker 2: and rage and a propensity to bite. The virus also
Speaker 2: moves into the salivary glands and in this way it's
Speaker 2: passed on through the bite to the next host. So
Speaker 2: by maneuvering the behavior of the animal, this is how
Speaker 2: the virus ensures it spread to other hosts. So just
Speaker 2: think about that the virus, a measly seventy five billions
Speaker 2: of a meter in diameter, survives by command during the
Speaker 2: massive body of an animal, an animal twenty five million
Speaker 2: times larger than it. It would be like you finding
Speaker 2: a creature that's twenty eight one thousand miles tall and
Speaker 2: doing something very clever to bend its will to yours,
Speaker 2: and then you drive it around.
Speaker 1: The critical take home.
Speaker 2: Lesson here is that invisibly small changes inside the brain
Speaker 2: can cause massive changes to behavior. Our choices are inseparably
Speaker 2: married to the tiniest details of our machinery. And as
Speaker 2: another example of our dependence on our biology, note that
Speaker 2: tiny mutations in single genes also determine and change or behavior.
Speaker 2: Consider Huntington's disease, in which creeping damage in the frontal
Speaker 2: cortex leads to changes in personality such as aggressiveness and hypersexuality,
Speaker 2: and impulsive behavior and disregard for social norms, all happening
Speaker 2: years before the more recognizable symptom of spastic limb movement
Speaker 2: ever appears. The point to appreciate is that Huntington's is
Speaker 2: caused by a mutation.
Speaker 1: In a single gene.
Speaker 2: My colleague Robert Supolski summarized the situation in Huntington's like
Speaker 2: this quote. Alter one gene among tens of thousands, and
Speaker 2: approximately halfway through one's life there occurs a dramatic transformation
Speaker 2: of personality. So, in the face of all these observations
Speaker 2: we've talked about, can we conclude anything other than a
Speaker 2: dependence of our essence on the details of our biology.
Speaker 2: Could you tell a person with Huntingtons to just use
Speaker 2: his free will to quit acting so strangely? So we
Speaker 2: can see that the invisibly small molecules that we call
Speaker 2: narcotics or neurotransmitters, or hormones or viruses or genes, these
Speaker 2: can all place their little hands on the steering wheel
Speaker 2: of our behavior. As soon as your drink is spiked,
Speaker 2: or your sandwich gets sneezed on, or your genome picks
Speaker 2: up a mutation, your ship can move in a different direction,
Speaker 2: try as we might to make it otherwise, the changes
Speaker 2: in our machinery equate to changes in us. Given these
Speaker 2: facts on the ground, it's far from clear that we
Speaker 2: hold the option of choosing who we would like to be.
Speaker 2: As my friend Martha Farah puts it, quote, if an
Speaker 2: antidepressant pill can help us take everyday problems in stride,
Speaker 2: and if a stimulant can help us meet our deadlines
Speaker 2: and keep our commitments at work, then must not unflappable
Speaker 2: temperaments and conscientious characters also be features of people's bodies.
Speaker 2: And if so, is there anything about people that is
Speaker 2: not a feature of their bodies?
Speaker 1: End quote?
Speaker 2: So, where we are now, as we've established the connection
Speaker 2: between your biology and who you are, But this depends
Speaker 2: on such a vast network of factors that it's presumably
Speaker 2: going to remain impossible to make a one to one
Speaker 2: mapping between molecules and behavior. And this is what we're
Speaker 2: going to dig into in the next episode. But despite
Speaker 2: this complexity, we can conclude that your world is directly
Speaker 2: tied to your biology. If there could even exist something
Speaker 2: like a soul, we'd have to conclude at minimum that
Speaker 2: it is tangled irreversibly with the molecular and cellular details.
Speaker 2: Whatever else might be going on with our mysterious existence.
Speaker 2: The fact is that your essence is irreversibly yoked to
Speaker 2: your biology.
Speaker 1: That is beyond doubt.
Speaker 2: So join me next week for part two, when we're
Speaker 2: going to go to the next level and reveal some surprises.
Speaker 1: To find out more and to share your thoughts, head over.
Speaker 2: To egoman dot com slash podcasts. Send me an email
Speaker 2: at podcasts at eagleman dot com with questions or discussions,
Speaker 2: and I'll be making episodes in which I address those
Speaker 2: until next time. I'm David Eagleman, and this is Inner Cosmos.