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  • In the early 1800's, German physician, Franz Joseph Gall spent a lot of time running his

  • fingers over the scalps of strangers. He wasn't a hairdresser, he wasn't a masseuse,

  • he wasn't just like a big fan of heads. He was a phrenologist, he was the first phrenologist.

  • Gall believed that a persons personality was linked to their skull morphology, that its bumps and ridges

  • indicated aspects of their character. Amazingly this "science" actually caught on,

  • was widely practiced for decades, and Gall became something of a celebrity.

  • Well, with a head like his, one can see how he might have been a little bit fixated with skull shape.

  • Eventually, phrenology was dismissed as a cult pseudoscience because it turns out your

  • cranial contours tell us exactly nothing about what's happening inside the brain.

  • And yet! Gall was actually on to something big, something that we knew nothing about.

  • Remember, at this point we were just starting to get consensus that the brain was the source

  • of self and not like the soul or the heart or whatever. His lasting and correct proposition

  • was that different parts of the brain control specific aspects of our behavior.

  • Like we talked about last time, there is a strong link between biological activity and psychological events.

  • But in addition to the interplay of chemicals like neurotransmitters and hormones,

  • a lot of this has to do with that localized parts of the brain have specific functions,

  • like vision, movement, memory, speech, and even facial recognition.

  • Function, in other words, is localized.

  • If you could stimulate different parts of my brain in any way you wanted to

  • and if you ask me nicely, I just might let youyou could control my movements, my memories,

  • and even my personality. Poke my brain over here and my arm would twitch, poke here and

  • I'd remember my first kiss, do it up here and suddenly I'd be filled with a tremendous Hulk-like rage!

  • This is the link between the brain, that physical hunk of gunk between the ears, and the mind,

  • the thing that is us, our consciousness, our behavior, our decisions, our memories, our selves.

  • Some neuroscientists like to say that the mind is what the brain does, so one of

  • the driving questions of psychology and, like, the human experiment is "How do our brains'

  • functions tie to the behavior of the mind?" And you can't even ask the right questions,

  • let alone get at some of the answers, until you get to know the brain.

  • [Intro]

  • You might have a passing familiarity with your nervous system, like, "The brain bone

  • is connected to the spinal cord bone, and the spinal cord bone is connected to the motoneuron bone."

  • That's your central nervous system, and there aren't actually any bones.

  • Your central nervous system, or just CNS, is what makes your bodies big decisions.

  • This system is the command center, and if you mess with it, things are gonna get weird.

  • There's also the peripheral nervous system, which is composed of scout-like sensory neurons

  • that gather information and report it back to the central nervous system.

  • To get a handle on just how physical the roots of your mind and personality are,

  • how concretel your nervous system makes you you, let me tell you a story. The curious case of Phineas Gage.

  • In 1848, a genial chap named Phineas Gage was working on the railroad,

  • tamping gunpowder into a blasting hole with an iron rod, but the gunpowder ignited.

  • The resulting explosion caused the rod to shoot like a bullet up through his left cheek and out of the top of his head.

  • There's brain in between those two places, by the way.

  • Amazingly, he stood up after the accident, and walked over to a cart, described what had happened,

  • and then they drove him back to his house, all while he was conscious.

  • So the doctor came to examine him, and refused to believe that a rod had in fact passed through his head, understandably.

  • Until Phineas started coughing and an amount of brain that the doctor described

  • as a teacup-ful fell out of his head, and the doctor had to accept indeed what had happened.

  • After a few months of convalescing, he was pretty much healed up and moving around

  • like he used to. But his friends were saying that Phineas was no longer like himself.

  • Yes he had his memories and his mental abilities, and he walked and talked and looked the same,

  • minus an eyeball, whereas the old Phineas was mild-mannered and soft-spoken, the post-spike-to-the-brain Phineas

  • was surly and mean-spirited and vulgar. People started to describe him as "no longer Gage"

  • Phineas moved away from America, the scientific establishment lost contact with him

  • and 12 years later, after a series of seizures he died at the age of 36.

  • Phineas is a great, if extreme, example of how function is localized in the brain and how physical and biological

  • factors can be reflected in psychological ways. Of course he is also an excellent example

  • of how individual studies are not particularly useful, especially since we have very little

  • data on what Phineas was actually like before or even after his accident.

  • Most accounts are from the months directly after the accident, and many of them conflict.

  • It's completely possible that he continued to heal and lived his remaining years as a happy and productive citizen.

  • Intro-psychology texts often paint the simple picture of Phineas just so we can have a clear

  • example of the moment when physicians realized that messing with the brain was messing with the mind,

  • but it is of course all much more complicated and Phineas was an actual, real life person,

  • I feel that we should give him the nuance and mystery that he deserves.

  • Now you might have heard that we only used about 10 percent of our brains,

  • and oh if that were true, Phineas would lose a quarter of his and he'd be just fine. And if we could

  • just harness the rest of that gray mush, we'd be able to mind read and levitate and get all Professor X.

  • It's an exciting thought, as exciting as the idea that I can tell what

  • kind of tea you like by feeling the bumps on your head. It is also exactly as wrong.

  • After watching an hour or so of reality TV, you'd be forgiven for thinking that some people

  • are only working at 10 percent brain capacity. But in actual reality, brain scans show that

  • nearly every region of the brain lights up during even simple tasks like walking and talking.

  • Not only that, but the brain itself requires 20 percent of all the body's energy,

  • and it would make little evolutionary sense to throw much energy away at something that is only minimally active.

  • As animals, our capabilities have developed in part from our brain structures.

  • We're actually able to trace our evolutionary history as we come to understand these structures.

  • Less complex animals have simpler brains designed for basic functioning and survival:

  • rest, breathe, eat. Whereas more complex animals like many mammals possess brains that feel,

  • remember, reason, and predict. These animals don't have all new systems.

  • They have new brain systems built upon old brain systems. The brain is kind of like a set of Russian nesting dolls.

  • The outermost wooden doll is the newest, most detailed and most complex,

  • but as you go deeper, the dolls become older and smaller, and simpler, and more generic.

  • The innermost wooden doll is the oldest, most basic. It's like a fossil in your head.

  • This inner core of the brain, sometimes called the "old brain" still performs for us much

  • as it did for our early evolutionary ancestors. It's anchored by the brainstem, the most ancient

  • and central core of the brain where the spinal brain enters the skull. Above it, at the base

  • of the skull, is the medulla. Here, old brain functions happen automatically without any conscious effort:

  • the beating of hearts, the breathing of lungs, that sort of thing.

  • The pons is perched on the medulla, and it helps coordinate movement. Above the pons,

  • at the top of the brainstem, is the thalamus, a pair of egg-shaped structures that take in

  • sensory information related to seeing, hearing, touching, and tasting. The reticular formation is a

  • finger-shaped nerve network inside the brain stem that's essential for arousal,

  • which isn't necessarily what you feel upon seeing a particularly nice-looking human, but instead refers to

  • things like sleeping and walking and pain perception; other important functions.

  • The baseball-sized cerebellum, or "little brain", swells from the bottom of the brain stem and

  • is responsible for non-verbal learning and memory, the perception of time, and modulating motions,

  • it controls voluntary movement like your sweet dance moves, but it also gets impaired

  • easily under the influence of alcohol, hence the term "tipsy".

  • So the old brain systems keep our body's basic functions running smoothly; the sort of stuff any animal might need.

  • This is pretty much where the brain stops for reptiles.

  • For higher functions, we look to the limbic system. This includes the amygdala, hypothalamus, and hippocampus.

  • Sort of a border region of the brain separating the old brain and the newer, higher cerebral areas.

  • The amygdala consists of two lima bean-sized clusters of neurons

  • and is responsible for memory consolidation as well as both our greatest fear and hottest aggression.

  • Stimulate one area of the amygdala, and a docile family dog suddenly morphs into a blood thirsty Cujo.

  • Shift that electrode over just a tiny bit and that dog will be

  • cowering at butterfly shadow puppets. The hypothalamus keeps your whole body steady,

  • regulating body temperatures, circadian rhythms, and hunger, also helps govern the endocrine system,

  • especially the pituitary gland. You should also thank your hypothalamus for allowing

  • you to feel pleasure and reward. Rats implanted with electrodes in the reward center of their hypothalamuses

  • and given ways to self stimulate those areas will essentially reward themselves

  • until they collapse or die. So, use with caution. The final part of the limbic system is the hippocampus,

  • central to learning and memory, and if it's damaged, a person may lose their ability

  • to retain new facts and memories.

  • Now above all of this is the most advanced stuff - the stuff that you think of when you

  • think of the brain - the grey matter. The two hemispheres of your cerebrum make up about

  • eighty-five percent of your brain weight, and oversee your ability to think, speak, and perceive.

  • The left and right hemispheres govern and regulate different functions,

  • giving us a split brain, connected by a structure called the corpus callosum. So, for instance,

  • language production is controlled largely by the left hemisphere, while certain creative

  • functions are controlled by the right. Though this has nothing to do with handedness or

  • people having dominant sides of their brain being more analytical or creative or whatever

  • - that's part of what we call pop psychology: a behavioral disorder in which journalists

  • and arm chair psychologists use research showing beautiful, detailed, intimately connected

  • complexities of your brain to sell newspapers or reinforce previously held beliefs.

  • Yes, some tasks are distributed to one side, but the sides are deeply and constantly connected;

  • a statement as general as "artistic people use their right brains" is as useless as saying

  • "artistic people have particularly bumpy heads".

  • Finally, covering the left and right hemispheres, we have the cerebral cortex, a thin layer

  • of over twenty billion interconnected neurons. But let's not forget the unsung heroes of

  • your nervous system: the billions of non-neuron glial cells, which provide a spider web of

  • support that surround, insulate, and nourish the cerebral neurons.

  • You've probably seen enough brain diagrams to know that the cerebral cortex's left and

  • right sides are subdivided into four lobes: the frontal, parietal, occipital, and temporal,

  • all separated by especially prominent folds, or fissures. Each lobe does indeed have its

  • own set of duties, and would have made Franz Gall proud.

  • The frontal lobes, just behind your forehead, are involved in speaking, planning, judging, abstract thinking,

  • and as the tale of Phineas Gage reminds us, aspects of personality.

  • The parietal lobes receive and process your sense of touch and body position.

  • At the back of your head, the occipital lobes receive information related to sight.

  • And the temporal lobes just above your ears process sound, including speech comprehension.

  • Remember that each hemisphere controls the opposite side of the body, so my left temporal

  • lobe processes sounds heard through my right ear. And within these lobes there are still

  • more regions that have specialized functions. Your motor cortex at the rear of your frontal lobes,

  • for example, controls voluntary movements and sends messages from the brain out to the body

  • like "pet that dog!" or "pick up that mug", while your somatosensory cortex right

  • behind it processes incoming sensations like "Oooooh, that doggie is soft!"

  • or "Gah, the mug is hot!"

  • The rest of your grey matter is made up of association areas that are related to higher

  • mental functions like remembering, thinking, learning, and speaking. But the thing about

  • association areas is that unlike your sensory or motor cortex, you couldn't just poke one

  • and create a neat response. Association areas are more subtle; they deal with things like

  • interpreting and integrating sensory input and linking up with memories. And they prevail throughout all four lobes,

  • so brain damage to different areas will cause very different results.

  • A lesion on a specific part of the temporal lobe may destroy a person's ability to recognize faces;

  • traumatic memories or overactive hormones can profoundly affect our behavior and emotions

  • - all of which remind us how fundamentally <