Meet Your Master - Getting to Know Your Brain: Crash Course Psychology #4 — Transcript

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1. 0:00In the early 1800's, German physician, Franz Joseph Gall spent a lot of time running his
2. 0:05fingers over the scalps of strangers. He wasn't a hairdresser, he wasn't a masseuse, he wasn't
3. 0:10just like a big fan of heads. He was a phrenologist, he was the first phrenologist. Gall believed
4. 0:15that a persons personality was linked to their skull morphology, that its bumps and ridges
5. 0:20indicated aspects of their character. Amazingly this "science" actually caught on, was widely
6. 0:25practiced for decades, and Gall became something of a celebrity.
7. 0:30Well, with a head like his, one can see how he might have been a little bit fixated with
8. 0:35skull shape.
9. 0:35Eventually, phrenology was dismissed as a cult pseudoscience because it turns out your
10. 0:39cranial contours tell us exactly nothing about what's happening inside the brain.
11. 0:43And yet! Gall was actually on to something big, something that we knew nothing about.
12. 0:47Remember, at this point we were just starting to get consensus that the brain was the source
13. 0:52of self and not like the soul or the heart or whatever. His lasting and correct proposition
14. 0:57was that different parts of the brain control specific aspects of our behavior.
15. 1:01Like we talked about last time, there is a strong link between biological activity and
16. 1:05psychological events. But in addition to the interplay of chemicals like neurotransmitters
17. 1:09and hormones, a lot of this has to do with that localized parts of the brain have specific
18. 1:14functions, like vision, movement, memory, speech, and even facial recognition. Function,
19. 1:18in other words, is localized.
20. 1:20If you could stimulate different parts of my brain in any way you wanted to– and if
21. 1:23you ask me nicely, I just might let you– you could control my movements, my memories,
22. 1:27and even my personality. Poke my brain over here and my arm would twitch, poke here and
23. 1:32I'd remember my first kiss, do it up her and suddenly I'd be filled with a tremendous Hulk-like
24. 1:36rage!
25. 1:36This is the link between the brain, that physical hunk of gunk between the ears, and the mind,
26. 1:42the thing that is us, our consciousness, our behavior, our decisions, our memories, our
27. 1:47selves. Some neuroscientists like to say that the mind is what the brain does, so one of
28. 1:52the driving questions of psychology and, like, the human experiment is "How do our brains'
29. 1:57functions tie to the behavior of the mind?" And you can't even ask the right questions,
30. 2:02let alone get at some of the answers, until you get to know the brain.
31. 2:08[Intro]
32. 2:12You might have a passing familiarity with your nervous system, like, "The brain bone
33. 2:19is connected to the spinal cord bone, and the spinal cord bone is connected to the motoneuron
34. 2:23bone." That's your central nervous system, and there aren't actually any bones. Your
35. 2:27central nervous system, or just CNS, is what makes your bodies big decisions. This system
36. 2:32is the command center, and if you mess with it, things are gonna get weird. There's also
37. 2:35the peripheral nervous system, which is composed of scout-like sensory neurons that gather
38. 2:39information and report it back to the central nervous system.
39. 2:42To get a handle on just how physical the roots of your mind and personality are, how concretely
40. 2:47your nervous system makes you you, let me tell you a story. The curious case of Phineas
41. 2:52Gage. In 1848, a genial chap named Phineas Gage was working on the railroad, tamping
42. 2:58gunpowder into a blasting hole with an iron rod, but the gunpowder ignited.The resulting
43. 3:02explosion caused the rod to shoot like a bullet up through his left cheek and out of the top
44. 3:07of his head. There's brain in between those two places, by the way. Amazingly, he stood
45. 3:12up after the accident, and walked over to a cart, described what had happened, and then
46. 3:17they drove him back to his house, all while he was conscious.
47. 3:20So the doctor came to examine him, and refused to believe that a rod had in fact passed through
48. 3:25his head, understandably. Until Phineas started coughing and an amount of brain that the doctor
49. 3:31described as a teacup-ful fell out of his head, and the doctor had to accept indeed
50. 3:37what had happened. After a few months of convalescing, he was pretty much healed up and moving around
51. 3:41like he used to. But his friends were saying that Phineas was no longer like himself. Yes
52. 3:47he had his memories and his mental abilities, and he walked and talked and looked the same,
53. 3:52minus an eyeball, whereas the old Phineas was mild-mannered and soft-spoken, the post-spike-to-the-brain
54. 3:57Phineas was surly and mean-spirited and vulgar. People started to describe him as "no longer
55. 4:03Gage."
56. 4:04Phineas moved away from America, the scientific establishment lost contact with him and 12
57. 4:08years later, after a series of seizures he died at the age of 36. Phineas is a great,
58. 4:13if extreme, example of how function is localized in the brain and how physical and biological
59. 4:17factors can be reflected in psychological ways. Of course he is also an excellent example
60. 4:21of how individual studies are not particularly useful, especially since we have very little
61. 4:26data on what Phineas was actually like before or even after his accident. Most accounts
62. 4:30are from the months directly after the accident, and many of them conflict. It's completely
63. 4:34possible that he continued to heal and lived his remaining years as a happy and productive
64. 4:38citizen.
65. 4:38Intro-psychology texts often paint the simple picture of Phineas just so we can have a clear
66. 4:42example of the moment when physicians realized that messing with the brain was messing with
67. 4:46the mind, but it is of course all much more complicated and Phineas was an actual, real
68. 4:51life person, I feel that we should give him the nuance and mystery that he deserves.
69. 4:55Now you might have heard that we only used about 10 percent of our brains, and oh if
70. 4:58that were true, Phineas would lose a quarter of his and he'd be just fine. And if we could
71. 5:03just harness the rest of that gray mush, we'd be able to mind read and levitate and get
72. 5:07all Professor X. It's an exciting thought, as exciting as the idea that I can tell what
73. 5:11kind of tea you like by feeling the bumps on your head. It is also exactly as wrong.
74. 5:15After watching an hour or so of reality TV, you'd be forgiven for thinking that some people
75. 5:19are only working at 10 percent brain capacity. But in actual reality, brain scans show that
76. 5:23nearly every region of the brain lights up during even simple tasks like walking and
77. 5:27talking. Not only that, but the brain itself requires 20 percent of all the body's energy,
78. 5:32and it would make little evolutionary sense to throw much energy away at something that
79. 5:36is only minimally active.
80. 5:37As animals, our capabilities have developed in part from our brain structures. We're actually
81. 5:41able to trace our evolutionary history as we come to understand these structures. Less
82. 5:45complex animals have simpler brains designed for basic functioning and survival: rest,
83. 5:50breathe, eat. Whereas more complex animals like many mammals possess brains that feel,
84. 5:55remember, reason, and predict. These animals don't have all new systems. They have new
85. 5:59brain systems built upon old brain systems. The brain is kind of like a set of Russian
86. 6:03nesting dolls. The outermost wooden doll is the newest, most detailed and most complex,
87. 6:08but as you go deeper, the dolls become older and smaller, and simpler, and more generic.
88. 6:13The innermost wooden doll is the oldest, most basic. It's like a fossil in your head.
89. 6:18This inner core of the brain, sometimes called the "old brain" still performs for us much
90. 6:22as it did for our early evolutionary ancestors. It's anchored by the brainstem, the most ancient
91. 6:27and central core of the brain where the spinal brain enters the skull. Above it, at the base
92. 6:32of the skull, is the medulla. Here, old brain functions happen automatically without any
93. 6:36conscious effort: the beating of hearts, the breathing of lungs, that sort of thing. The
94. 6:40pons is perched on the medulla, and it helps coordinate movement. Above the pons, at the
95. 6:45top of the brainstem, is the thalamus, a pair of egg-shaped structures that take in sensory
96. 6:50information related to seeing, hearing, touching, and tasting. The reticular formation is a
97. 6:54finger-shaped nerve network inside the brain stem that's essential for arousal, which isn't
98. 6:58necessarily what you feel upon seeing a particularly nice-looking human, but instead refers to
99. 7:03things like sleeping and walking and pain perception; other important functions. The
100. 7:06baseball-sized cerebellum, or "little brain", swells from the bottom of the brain stem and
101. 7:10is responsible for non-verbal learning and memory, the perception of time, and modulating
102. 7:14motions, it controls voluntary movement like your sweet dance moves, but it also gets impaired
103. 7:19easily under the influence of alcohol, hence the term "tipsy".
104. 7:22So the old brain systems keep our body's basic functions running smoothly; the sort of stuff
105. 7:27any animal might need. This is pretty much where the brain stops for reptiles.
106. 7:31For higher functions, we look to the limbic system. This includes the amygdala, hypothalamus,
107. 7:36and hippocampus. Sort of a border region of the brain separating the old brain and the
108. 7:40newer, higher cerebral areas. The amygdala consists of two lima bean-sized clusters of
109. 7:45neurons and is responsible for memory consolidation as well as both our greatest fear and hottest
110. 7:50aggression. Stimulate one area of the amygdala, and a docile family dog suddenly morphs into
111. 7:54a blood thirsty Cujo. Shift that electrode over just a tiny bit and that dog will be
112. 7:57cowering at butterfly shadow puppets. The hypothalamus keeps your whole body steady,
113. 8:02regulating body temperatures, circadian rhythms, and hunger, also helps govern the endocrine
114. 8:07system, especially the pituitary gland. You should also thank your hypothalamus for allowing
115. 8:10you to feel pleasure and reward. Rats implanted with electrodes in the reward center of their
116. 8:14hypothalamuses and given ways to self stimulate those areas will essentially reward themselves
117. 8:19until they collapse or die. So, use with caution. The final part of the limbic system is the
118. 8:25hippocampus, central to learning and memory, and if it's damaged, a person may lose their
119. 8:30ability to retain new facts and memories.
120. 8:32Now above all of this is the most advanced stuff - the stuff that you think of when you
121. 8:35think of the brain - the grey matter. The two hemispheres of your cerebrum make up about
122. 8:40eighty-five percent of your brain weight, and oversee your ability to think, speak,
123. 8:44and perceive. The left and right hemispheres govern and regulate different functions, giving
124. 8:48us a split brain, connected by a structure called the corpus callosum. So, for instance,
125. 8:53language production is controlled largely by the left hemisphere, while certain creative
126. 8:56functions are controlled by the right. Though this has nothing to do with handedness or
127. 9:01people having dominant sides of their brain being more analytical or creative or whatever
128. 9:05- that's part of what we call pop psychology: a behavioral disorder in which journalists
129. 9:10and arm chair psychologists use research showing beautiful, detailed, intimately connected
130. 9:14complexities of your brain to sell newspapers or reinforce previously held beliefs.
131. 9:19Yes, some tasks are distributed to one side, but the sides are deeply and constantly connected;
132. 9:24a statement as general as "artistic people use their right brains" is as useless as saying
133. 9:28"artistic people have particularly bumpy heads".
134. 9:31Finally, covering the left and right hemispheres, we have the cerebral cortex, a thin layer
135. 9:35of over twenty billion interconnected neurons. But let's not forget the unsung heroes of
136. 9:40your nervous system: the billions of non-neuron glial cells, which provide a spider web of
137. 9:45support that surround, insulate, and nourish the cerebral neurons.
138. 9:49You've probably seen enough brain diagrams to know that the cerebral cortex's left and
139. 9:52right sides are subdivided into four lobes: the frontal, parietal, occipital, and temporal,
140. 9:58all separated by especially prominent folds, or fissures. Each lobe does indeed have its
141. 10:03own set of duties, and would have made Franz Gall proud.
142. 10:06The frontal lobes, just behind your forehead, are involved in speaking, planning, judging,
143. 10:09abstract thinking, and as the tale of Phineas Gage reminds us, aspects of personality. The
144. 10:14parietal lobes receive and process your sense of touch and body position. At the back of
145. 10:18your head, the occipital lobes receive information related to sight. And the temporal lobes just
146. 10:22above your ears process sound, including speech comprehension.
147. 10:26Remember that each hemisphere controls the opposite side of the body, so my left temporal
148. 10:30lobe processes sounds heard through my right ear. And within these lobes there are still
149. 10:33more regions that have specialized functions. Your motor cortex at the rear of your frontal
150. 10:37lobes, for example, controls voluntary movements and sends messages from the brain out to the
151. 10:41body like "pet that dog!" or "pick up that mug", while your somatosensory cortex right
152. 10:45behind it processes incoming sensations like "Oooooh, that doggie is soft!" or "Gah, the
153. 10:50mug is hot!"
154. 10:50The rest of your grey matter is made up of association areas that are related to higher
155. 10:54mental functions like remembering, thinking, learning, and speaking. But the thing about
156. 10:58association areas is that unlike your sensory or motor cortex, you couldn't just poke one
157. 11:03and create a neat response. Association areas are more subtle; they deal with things like
158. 11:07interpreting and integrating sensory input and linking up with memories. And they prevail
159. 11:12throughout all four lobes, so brain damage to different areas will cause very different
160. 11:17results.
161. 11:17A lesion on a specific part of the temporal lobe may destroy a person's ability to recognize
162. 11:22faces; traumatic memories or overactive hormones can profoundly affect our behavior and emotions
163. 11:27- all of which remind us how fundamentally biology and psychology are intertwined. And
164. 11:32there are few more fascinating examples of this than how we sense and perceive the world
165. 11:36around us, so that's where we're gonna pick up next week.
166. 11:39For now, if you were paying attention, you learned the basics of the central nervous
167. 11:42system, specifically the brain, which can be understood in terms of old or of more evolutionary
168. 11:48ancestral structures, along with the limbic system, and new structures, which include
169. 11:53lobes, cortices, and association areas.
170. 11:55Thanks for watching this lesson in Crash Course Psychology, which was brought to you by The
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174. 12:12This episode was written by Kathleen Yale, edited by Blake de Pastino and myself, and
175. 12:16our consultant is Dr. Ranjit Bhagwat. Our editor and director is Nicholas Jenkins, Michael
176. 12:20Aranda is our sound designer and our graphic team is Thought Cafe.