1 00:00:00,140 --> 00:00:01,850 The following content is provided 2 00:00:01,850 --> 00:00:04,090 under a Creative Commons license. 3 00:00:04,090 --> 00:00:06,940 Your support will help MIT OpenCourseWare continue 4 00:00:06,940 --> 00:00:10,800 to offer high-quality educational resources for free. 5 00:00:10,800 --> 00:00:13,410 To make a donation or view additional materials 6 00:00:13,410 --> 00:00:17,310 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:17,310 --> 00:00:17,935 at ocw.mit.edu. 8 00:00:22,160 --> 00:00:27,040 PROFESSOR: We have a few more slides from last time 9 00:00:27,040 --> 00:00:30,710 to finish up because of the problems 10 00:00:30,710 --> 00:00:32,680 I had with the computer. 11 00:00:32,680 --> 00:00:35,720 We have a class Wednesday with a quiz. 12 00:00:35,720 --> 00:00:41,880 And Friday, as most of you know, it's a student holiday. 13 00:00:41,880 --> 00:00:46,460 I would encourage all of you to go to the career fair-- 14 00:00:46,460 --> 00:00:49,670 especially if you've not been to one before. 15 00:00:49,670 --> 00:00:53,640 Even if you fully expect to go to medical school or something 16 00:00:53,640 --> 00:00:55,000 like that-- you never know. 17 00:00:55,000 --> 00:00:56,920 You should know what's out there. 18 00:01:02,820 --> 00:01:05,940 All right we started talking about the ethology of geese 19 00:01:05,940 --> 00:01:11,390 last time, and we saw a video where 20 00:01:11,390 --> 00:01:13,380 you could see Konrad Lorenz and some 21 00:01:13,380 --> 00:01:18,500 of his early work discovering imprinting. 22 00:01:18,500 --> 00:01:22,590 They showed the work he'd done with geese. 23 00:01:22,590 --> 00:01:25,850 And then later, work on social behavior of geese 24 00:01:25,850 --> 00:01:30,090 and the role of early experience and learning. 25 00:01:37,112 --> 00:01:41,010 What was the answer to this question-- 26 00:01:41,010 --> 00:01:45,980 "Is the response of geese to an aerial predator innate?" 27 00:01:45,980 --> 00:01:52,740 In the video you saw this bird shape-- it was actually 28 00:01:52,740 --> 00:01:55,920 made to look quite a bit like a bird in that video, 29 00:01:55,920 --> 00:01:58,350 but you can use a silhouette-- that they 30 00:01:58,350 --> 00:02:00,010 glided above the birds. 31 00:02:00,010 --> 00:02:03,610 And the birds showed a mobbing reaction. 32 00:02:03,610 --> 00:02:07,100 They forget about their individual squabbles 33 00:02:07,100 --> 00:02:09,509 and whatever they had been doing, 34 00:02:09,509 --> 00:02:12,720 and they all pretty much do the same thing. 35 00:02:12,720 --> 00:02:17,070 And they protect their young and so forth. 36 00:02:17,070 --> 00:02:19,050 Is that an innate response? 37 00:02:19,050 --> 00:02:20,110 What did we see? 38 00:02:23,780 --> 00:02:27,460 Did they have an innate response to the shape 39 00:02:27,460 --> 00:02:29,455 of a hawk as opposed to a goose? 40 00:02:33,930 --> 00:02:37,835 Hawk shapes-- short neck, longer tail. 41 00:02:37,835 --> 00:02:41,610 The goose shape-- the duck shape-- long neck, 42 00:02:41,610 --> 00:02:43,740 shorter tail. 43 00:02:43,740 --> 00:02:49,340 So they make a very different silhouette when it's moving. 44 00:02:49,340 --> 00:02:53,290 Is that an innate response? 45 00:02:53,290 --> 00:02:55,220 There's still some claims in the literature 46 00:02:55,220 --> 00:02:59,000 that in perhaps some birds it is innate. 47 00:02:59,000 --> 00:03:02,060 And it's clear there are some innate responses made 48 00:03:02,060 --> 00:03:06,360 to overhead movement. 49 00:03:06,360 --> 00:03:09,190 But the precise shape they're responding to 50 00:03:09,190 --> 00:03:13,060 is probably not innate. 51 00:03:13,060 --> 00:03:16,040 That doesn't mean that birds don't have many innate 52 00:03:16,040 --> 00:03:19,880 responses to specific visual configurations, 53 00:03:19,880 --> 00:03:23,630 because they certainly do. 54 00:03:23,630 --> 00:03:26,620 Migrating birds, for example, can 55 00:03:26,620 --> 00:03:30,600 respond to the patterns of the stars. 56 00:03:30,600 --> 00:03:35,290 But in this case they're responding 57 00:03:35,290 --> 00:03:39,540 to slow, overhead movement, and the species 58 00:03:39,540 --> 00:03:41,790 may differ a little bit into the details 59 00:03:41,790 --> 00:03:44,940 of the movement they respond best to. 60 00:03:44,940 --> 00:03:48,580 But that doesn't mean it doesn't change with experience. 61 00:03:48,580 --> 00:03:49,600 They do. 62 00:03:49,600 --> 00:03:52,080 Depending on their experience, they can change. 63 00:03:55,570 --> 00:03:57,916 So that was this discussion. 64 00:04:01,560 --> 00:04:06,060 And this is the paper that did that-- a very nice analysis 65 00:04:06,060 --> 00:04:11,705 of the whole hawk/goose story-- because of some 66 00:04:11,705 --> 00:04:14,550 of the early work of Tinbergen and Lorenz, some of which 67 00:04:14,550 --> 00:04:19,899 they did together before World War II, where they met 68 00:04:19,899 --> 00:04:21,779 and spent the summer together working 69 00:04:21,779 --> 00:04:23,020 on this and other problems. 70 00:04:32,960 --> 00:04:37,540 Let's talk a little bit about human instincts, 71 00:04:37,540 --> 00:04:38,840 or fixed-action patterns. 72 00:04:41,810 --> 00:04:44,100 We know that yawning can be considered 73 00:04:44,100 --> 00:04:47,340 a human fixed-action pattern. 74 00:04:47,340 --> 00:04:49,720 Tends to be triggered by the yawning in other people, 75 00:04:49,720 --> 00:04:53,820 and it seems to have some kind of social meaning. 76 00:04:53,820 --> 00:04:56,915 It doesn't only mean that you feel tired. 77 00:04:56,915 --> 00:05:01,160 In fact, it has other meanings as well. 78 00:05:01,160 --> 00:05:03,000 And there's still some things about it 79 00:05:03,000 --> 00:05:04,530 we don't fully understand. 80 00:05:04,530 --> 00:05:05,780 But we do know it's inbuilt. 81 00:05:10,180 --> 00:05:14,020 These are their other examples. 82 00:05:14,020 --> 00:05:17,390 First of all, expressions of emotion. 83 00:05:17,390 --> 00:05:22,470 That was the work, remember, of Irenaus Eibl-Eibesfeld, where 84 00:05:22,470 --> 00:05:29,310 he studied emotional expressions in blind and deaf people. 85 00:05:29,310 --> 00:05:31,590 People born blind and deaf, found 86 00:05:31,590 --> 00:05:35,000 that they were the same as in normally 87 00:05:35,000 --> 00:05:37,380 sighted and hearing people. 88 00:05:37,380 --> 00:05:39,580 And he also studied across cultures. 89 00:05:39,580 --> 00:05:41,090 He went to cultures that had never 90 00:05:41,090 --> 00:05:45,100 seen Western expressions at all. 91 00:05:45,100 --> 00:05:52,140 And people in those cultures made all the very same types 92 00:05:52,140 --> 00:05:57,830 of expressions that you see in what 93 00:05:57,830 --> 00:05:59,560 we call the more developed cultures. 94 00:06:03,210 --> 00:06:06,100 Walking is an instinct. 95 00:06:06,100 --> 00:06:09,280 But don't we teach our children to walk? 96 00:06:09,280 --> 00:06:12,150 We always say that. 97 00:06:12,150 --> 00:06:18,940 "Oh, I've been teaching my child to walk, and he finally did it. 98 00:06:18,940 --> 00:06:22,730 He was a little bit slow to learn." 99 00:06:22,730 --> 00:06:26,280 Is this an accurate way of talking? 100 00:06:26,280 --> 00:06:26,780 Somebody? 101 00:06:30,430 --> 00:06:31,660 No. 102 00:06:31,660 --> 00:06:34,800 Because walking is instinctive behavior. 103 00:06:34,800 --> 00:06:42,040 The child starts walking because his nervous system has reached 104 00:06:42,040 --> 00:06:44,730 the state of maturity where the circuits underlying 105 00:06:44,730 --> 00:06:46,210 walking are mature enough. 106 00:06:46,210 --> 00:06:49,140 They're spinal circuits, primarily. 107 00:06:49,140 --> 00:06:50,780 Also hindbrain. 108 00:06:50,780 --> 00:06:51,970 That's what you need. 109 00:06:51,970 --> 00:06:54,170 You need the balance of a vestibular system 110 00:06:54,170 --> 00:06:56,705 and so forth, which is a hindbrain sense. 111 00:07:01,750 --> 00:07:04,710 But it's instinctive movement. 112 00:07:04,710 --> 00:07:08,180 Then I said that eye blinks and swallowing are actually 113 00:07:08,180 --> 00:07:11,060 fixed-action patterns, so they're normally 114 00:07:11,060 --> 00:07:13,560 called reflexes. 115 00:07:13,560 --> 00:07:18,840 So why would they be called fixed-action patterns and not 116 00:07:18,840 --> 00:07:20,690 reflexes? 117 00:07:20,690 --> 00:07:24,190 What do they need to be a fixed-action pattern and not 118 00:07:24,190 --> 00:07:27,160 a reflex? 119 00:07:27,160 --> 00:07:31,389 That could be on the quiz on Wednesday. 120 00:07:31,389 --> 00:07:32,680 There's got to be a difference. 121 00:07:32,680 --> 00:07:33,678 Yes? 122 00:07:33,678 --> 00:07:35,094 AUDIENCE: Fixed-action pattern has 123 00:07:35,094 --> 00:07:37,130 some type of motivations to it. 124 00:07:37,130 --> 00:07:39,310 PROFESSOR: OK, there's some motivation 125 00:07:39,310 --> 00:07:42,010 which builds up over time. 126 00:07:42,010 --> 00:07:46,360 So the longer you go without an eye blink 127 00:07:46,360 --> 00:07:50,130 or without swallowing, the more likely you are to do it. 128 00:07:50,130 --> 00:07:54,810 And it's difficult to go too long 129 00:07:54,810 --> 00:07:57,140 without blinking your eyes. 130 00:07:57,140 --> 00:07:59,149 I mean, there's a clear function to that. 131 00:07:59,149 --> 00:08:00,565 You need to lubricate the corneas. 132 00:08:04,230 --> 00:08:06,310 And we can stare at each other and see 133 00:08:06,310 --> 00:08:10,530 who blinks first, but in fact the motivation 134 00:08:10,530 --> 00:08:13,790 to blink-- the motivation goes up 135 00:08:13,790 --> 00:08:17,640 and up and up until the threshold for eliciting 136 00:08:17,640 --> 00:08:21,940 that response becomes very low, and almost anything 137 00:08:21,940 --> 00:08:24,810 can cause it. 138 00:08:24,810 --> 00:08:28,250 Of course we blink our eyes to protect our corneas not just 139 00:08:28,250 --> 00:08:32,490 from drying, but from other things too. 140 00:08:32,490 --> 00:08:35,510 If you puff air on it, that's the one 141 00:08:35,510 --> 00:08:38,724 that's normally called a reflex any touch of the cornea 142 00:08:38,724 --> 00:08:40,890 will elicit. 143 00:08:40,890 --> 00:08:43,070 But it also fits all the characteristics 144 00:08:43,070 --> 00:08:49,000 of an instinctive movement, a fixed-action pattern 145 00:08:49,000 --> 00:08:52,730 It doesn't normally respond to a sensory trigger, 146 00:08:52,730 --> 00:08:55,470 but it will occur with almost no trigger-- 147 00:08:55,470 --> 00:08:59,120 with very little trigger-- after enough time passed. 148 00:08:59,120 --> 00:09:01,550 And the same is true for swallowing. 149 00:09:01,550 --> 00:09:05,942 We don't swallow as often as we blink our eyes, 150 00:09:05,942 --> 00:09:09,090 but it still has many of the characteristics 151 00:09:09,090 --> 00:09:13,050 of a fixed-action pattern. 152 00:09:13,050 --> 00:09:17,580 And that we discussed a little bit here. 153 00:09:17,580 --> 00:09:22,520 So now let's go to another term common in ethology-- 154 00:09:22,520 --> 00:09:26,390 the concept of a supernormal stimulus. 155 00:09:26,390 --> 00:09:29,910 We say such a stimulus acts as a releaser 156 00:09:29,910 --> 00:09:31,315 of a fixed-action pattern. 157 00:09:35,600 --> 00:09:38,560 And I'm asking here for a fixed-action pattern in herring 158 00:09:38,560 --> 00:09:42,300 gull chicks, but you can think of other kinds 159 00:09:42,300 --> 00:09:44,295 of supernormal stimuli for other animals. 160 00:09:47,090 --> 00:09:50,430 So in the case of herring gulls, they 161 00:09:50,430 --> 00:09:54,690 have this conspicuous red orange spot-- pretty conspicuous-- 162 00:09:54,690 --> 00:09:58,350 you can see it there in the gull. 163 00:09:58,350 --> 00:10:00,226 That orange spot. 164 00:10:00,226 --> 00:10:01,805 It's seen better from below. 165 00:10:06,020 --> 00:10:09,070 And gull chicks respond to that spot 166 00:10:09,070 --> 00:10:16,070 when their parent is over them and moving. 167 00:10:19,710 --> 00:10:24,360 You can get an even stronger gaping response 168 00:10:24,360 --> 00:10:31,530 just by painting an orange spot on a yellow pencil 169 00:10:31,530 --> 00:10:32,630 and moving it a lot. 170 00:10:32,630 --> 00:10:34,340 You can get a stronger response. 171 00:10:34,340 --> 00:10:37,850 You can make it a supernormal stimulus 172 00:10:37,850 --> 00:10:40,295 by making it more prominent, by more movement. 173 00:10:42,840 --> 00:10:45,390 You can have perhaps greater contrast. 174 00:10:45,390 --> 00:10:48,240 But you can elicit that response even more. 175 00:10:48,240 --> 00:10:50,970 When you create a stronger response 176 00:10:50,970 --> 00:10:54,730 than normal with a slightly different stimulus, 177 00:10:54,730 --> 00:10:59,250 then we call it a supernormal stimulus. 178 00:10:59,250 --> 00:11:03,120 Another early discovery by ethologists 179 00:11:03,120 --> 00:11:07,010 was the supernormal stimulus in gulls 180 00:11:07,010 --> 00:11:10,740 to an egg that's rolled away from the nest, 181 00:11:10,740 --> 00:11:14,190 like a herring gull-- they nest on shore. 182 00:11:14,190 --> 00:11:18,660 An egg that rolls away from the other eggs, the bird 183 00:11:18,660 --> 00:11:22,830 reaches out and hooks his beak around it, 184 00:11:22,830 --> 00:11:26,590 and pulls it back into the nest by rolling it back in the nest. 185 00:11:26,590 --> 00:11:31,560 And if you make an egg larger than normal, 186 00:11:31,560 --> 00:11:36,800 he responds more strongly, shows more vigorous egg rolling. 187 00:11:36,800 --> 00:11:38,545 Serves as a supernormal stimulus. 188 00:11:41,930 --> 00:11:46,590 So then I want some examples in humans. 189 00:11:46,590 --> 00:11:50,270 Can you think of any supernormal stimuli in humans? 190 00:11:50,270 --> 00:11:54,870 We actually use them, yes, in advertising 191 00:11:54,870 --> 00:11:57,040 and social behavior. 192 00:11:57,040 --> 00:11:59,790 Let's start with foods. 193 00:11:59,790 --> 00:12:05,910 Foods that are especially sweet and high in fats 194 00:12:05,910 --> 00:12:07,910 serve as supernormal stimuli. 195 00:12:07,910 --> 00:12:11,220 We have an instinctive preference 196 00:12:11,220 --> 00:12:13,290 for sweeter and fatter foods. 197 00:12:17,870 --> 00:12:21,280 At least most of us do. 198 00:12:21,280 --> 00:12:23,620 And I put in here beware of restaurants, 199 00:12:23,620 --> 00:12:26,430 because there's a simple reason why 200 00:12:26,430 --> 00:12:28,650 I say beware in restaurants. 201 00:12:28,650 --> 00:12:32,310 The restaurant owner is in business. 202 00:12:32,310 --> 00:12:33,990 He wants to sell more food. 203 00:12:33,990 --> 00:12:38,690 He wants to sell food that attracts people. 204 00:12:38,690 --> 00:12:40,680 And the same is true of supermarkets. 205 00:12:40,680 --> 00:12:42,650 I say beware of supermarkets, too. 206 00:12:42,650 --> 00:12:44,480 I always read the label. 207 00:12:44,480 --> 00:12:50,185 For example, when I buy a jam, I read all these different jams 208 00:12:50,185 --> 00:12:52,020 that are lined up on the shelf. 209 00:12:52,020 --> 00:12:55,290 I read calories per tablespoon. 210 00:12:55,290 --> 00:12:58,160 50 every one. 211 00:12:58,160 --> 00:13:01,250 And then you read the details and you find out why. 212 00:13:01,250 --> 00:13:05,680 They've added high fructose corn syrup to it-- 213 00:13:05,680 --> 00:13:09,080 one of the most common ingredients 214 00:13:09,080 --> 00:13:12,550 in the American supermarket is high fructose corn syrup. 215 00:13:12,550 --> 00:13:13,350 Why? 216 00:13:13,350 --> 00:13:14,450 Because it's sweet. 217 00:13:14,450 --> 00:13:19,340 Because people like it better when it's sweet. 218 00:13:19,340 --> 00:13:22,640 And because I'm diabetic, I don't want the 50 calories. 219 00:13:22,640 --> 00:13:24,020 I want it to be natural. 220 00:13:24,020 --> 00:13:26,180 I don't want artificial sweetener either. 221 00:13:29,000 --> 00:13:32,130 So I prefer to make the jam myself, or find 222 00:13:32,130 --> 00:13:34,425 one that doesn't add that. 223 00:13:34,425 --> 00:13:38,150 They even will say "all natural" on it sometimes, 224 00:13:38,150 --> 00:13:39,722 and they'll still add sugar. 225 00:13:39,722 --> 00:13:41,180 They'll say, well, sugar's natural. 226 00:13:43,820 --> 00:13:47,960 Anyway, it's because it's instinctive 227 00:13:47,960 --> 00:13:50,490 that it's used to make more money. 228 00:13:54,070 --> 00:13:57,890 Think of the stimuli in sexual attraction. 229 00:13:57,890 --> 00:14:00,290 We call it the "poster effect" in advertising. 230 00:14:03,180 --> 00:14:07,240 When they advertise cars or other products, 231 00:14:07,240 --> 00:14:11,320 they often use a beautiful woman in the ad. 232 00:14:11,320 --> 00:14:12,110 Why? 233 00:14:12,110 --> 00:14:13,995 Just to attract attention. 234 00:14:13,995 --> 00:14:17,730 They're trying to sell it. 235 00:14:17,730 --> 00:14:19,787 They put them on posters even if they 236 00:14:19,787 --> 00:14:21,245 have nothing to do with the product 237 00:14:21,245 --> 00:14:25,520 that they're actually advertising-- 238 00:14:25,520 --> 00:14:26,670 with a beautiful smile. 239 00:14:26,670 --> 00:14:29,520 That helps, too, because we have an instinctive response 240 00:14:29,520 --> 00:14:31,510 to that. 241 00:14:31,510 --> 00:14:34,980 What about enhancements of appearance? 242 00:14:34,980 --> 00:14:39,894 How has male appearance been enhanced in men? 243 00:14:39,894 --> 00:14:41,560 Of course, we exaggerate shoulder width. 244 00:14:41,560 --> 00:14:45,080 We create suits, we put shoulder pads in. 245 00:14:45,080 --> 00:14:47,130 I mean, men already have broader shoulders 246 00:14:47,130 --> 00:14:52,490 than women on average, but to enhance 247 00:14:52,490 --> 00:14:53,930 that we add shoulder pads. 248 00:14:59,440 --> 00:15:03,570 In medieval costumes, it was common to enhance 249 00:15:03,570 --> 00:15:07,550 the penis area by putting this cowl-- often 250 00:15:07,550 --> 00:15:09,160 in a different color. 251 00:15:09,160 --> 00:15:11,340 And you see it in Shakespearean plays 252 00:15:11,340 --> 00:15:15,750 if they have period customs. 253 00:15:15,750 --> 00:15:22,580 In primitive tribes you often see-- for example, many of them 254 00:15:22,580 --> 00:15:25,090 use this-- sometimes the only clothing they wear 255 00:15:25,090 --> 00:15:28,110 is a penis sheath if they're males. 256 00:15:28,110 --> 00:15:34,460 Enhance the whole appearance-- usually of an erect penis. 257 00:15:34,460 --> 00:15:39,170 But it's just part of the costume. 258 00:15:39,170 --> 00:15:40,590 So another enhancement. 259 00:15:40,590 --> 00:15:44,270 It's creating a kind of supernormal stimulus. 260 00:15:44,270 --> 00:15:47,540 Female, it's even easier to think of these things. 261 00:15:47,540 --> 00:15:51,840 The waist-to-hip ratio-- men have a natural response 262 00:15:51,840 --> 00:15:55,195 to young women with a certain waist-to-hip ratio. 263 00:15:55,195 --> 00:15:57,230 We'll talk about that when we talk 264 00:15:57,230 --> 00:15:59,365 about research in sociobiology. 265 00:16:02,100 --> 00:16:05,780 But girdles and bustles were invented in order 266 00:16:05,780 --> 00:16:08,060 to enhance that. 267 00:16:08,060 --> 00:16:11,100 Of course, breast prominence-- that's still pretty common, 268 00:16:11,100 --> 00:16:15,640 especially in young girls-- you see it in high school. 269 00:16:15,640 --> 00:16:21,870 But it occurs almost everywhere in women of different ages. 270 00:16:21,870 --> 00:16:24,710 Think of other aspects-- lip color. 271 00:16:24,710 --> 00:16:27,575 Why is lip color enhanced? 272 00:16:27,575 --> 00:16:29,450 Why do women wear lipstick-- and in fact 273 00:16:29,450 --> 00:16:32,950 they enlarge the lips sometimes. 274 00:16:32,950 --> 00:16:34,310 What is that related to? 275 00:16:36,980 --> 00:16:38,740 You don't know? 276 00:16:38,740 --> 00:16:39,970 You do it, right? 277 00:16:39,970 --> 00:16:41,350 Some of you do. 278 00:16:41,350 --> 00:16:44,570 You know why? 279 00:16:44,570 --> 00:16:46,160 You know, you don't have to know why. 280 00:16:46,160 --> 00:16:50,170 When it comes to instincts, you don't have to know why. 281 00:16:50,170 --> 00:16:51,670 It's built-in. 282 00:16:51,670 --> 00:16:54,800 You don't have to know where it came from. 283 00:16:54,800 --> 00:16:58,170 Well, in sexual arousal, lips become redder and larger. 284 00:17:01,280 --> 00:17:04,240 So it elicits this response-- especially 285 00:17:04,240 --> 00:17:05,520 from the opposite sex. 286 00:17:11,619 --> 00:17:16,950 Why would shoulder size be enhanced in women? 287 00:17:16,950 --> 00:17:20,109 I can think of one possibility that 288 00:17:20,109 --> 00:17:21,635 would fit what we've been saying. 289 00:17:21,635 --> 00:17:29,160 And one is simply that the hourglass shape is not 290 00:17:29,160 --> 00:17:32,730 just waist-to-hip ratio, but it's the whole enhancement 291 00:17:32,730 --> 00:17:36,430 of a narrow waist by make the shoulders a little wider. 292 00:17:36,430 --> 00:17:38,890 But I think there's other reasons in modern culture. 293 00:17:38,890 --> 00:17:42,090 In fact, it's become much more common in modern culture 294 00:17:42,090 --> 00:17:46,780 than it was many years ago. 295 00:17:46,780 --> 00:17:51,740 And that is that women want to de-feminize 296 00:17:51,740 --> 00:17:53,340 their appearance somewhat. 297 00:17:53,340 --> 00:17:56,990 They want to be more like men. 298 00:17:56,990 --> 00:17:58,600 Now we don't think of it that way 299 00:17:58,600 --> 00:18:00,880 so much, but certainly when women first 300 00:18:00,880 --> 00:18:04,860 began to enter the business world a lot more. 301 00:18:04,860 --> 00:18:09,580 When did women really enter the world of business 302 00:18:09,580 --> 00:18:12,570 and the world of labor? 303 00:18:12,570 --> 00:18:17,550 During the wars, when all the men were going off to war. 304 00:18:17,550 --> 00:18:21,860 The economy would have fallen apart. 305 00:18:21,860 --> 00:18:27,910 So older men that were not going to the war, they needed help. 306 00:18:27,910 --> 00:18:33,540 So women came in and took over a lot of those jobs. 307 00:18:33,540 --> 00:18:38,960 But now, of course, women are at every level in business-- 308 00:18:38,960 --> 00:18:41,620 including right up to the top. 309 00:18:41,620 --> 00:18:45,990 But it's still fairly common for a business woman 310 00:18:45,990 --> 00:18:50,760 to wear suits that look like male suits. 311 00:18:50,760 --> 00:18:54,020 All right, well, anyway that's a somewhat separate reason 312 00:18:54,020 --> 00:18:56,295 that has nothing to do with supernormal stimuli. 313 00:18:56,295 --> 00:18:58,153 It has to do with kind of imitation. 314 00:19:01,280 --> 00:19:04,600 Then Scott in your textbook, he's 315 00:19:04,600 --> 00:19:06,290 talking about controlling behavior-- 316 00:19:06,290 --> 00:19:08,570 the role of the nervous system. 317 00:19:08,570 --> 00:19:11,800 And I would like you to at least know 318 00:19:11,800 --> 00:19:15,100 simple definitions of neurons and nervous systems 319 00:19:15,100 --> 00:19:18,370 so we can talk more easily about it. 320 00:19:18,370 --> 00:19:20,570 So I'm asking you for definitions 321 00:19:20,570 --> 00:19:26,080 of a primary sensory neuron, a secondary sensory neuron, 322 00:19:26,080 --> 00:19:28,210 a motor neuron, an interneuron. 323 00:19:28,210 --> 00:19:30,940 How do we define those things? 324 00:19:30,940 --> 00:19:31,810 You should all know. 325 00:19:31,810 --> 00:19:34,808 You've all had 901. 326 00:19:34,808 --> 00:19:36,280 Or you're taking it now. 327 00:19:39,110 --> 00:19:41,730 But maybe you didn't learn it, because they're not always 328 00:19:41,730 --> 00:19:47,520 so attentive to neuroanatomical details as I am. 329 00:19:47,520 --> 00:19:50,610 So let me give you some definitions. 330 00:19:50,610 --> 00:19:53,740 A primary sensory neuron is a neuron 331 00:19:53,740 --> 00:19:58,380 with a cell body outside the brain or spinal cord-- 332 00:19:58,380 --> 00:20:01,500 the central nervous system is brain and spinal cord-- 333 00:20:01,500 --> 00:20:04,940 the peripheral nervous system are outside. 334 00:20:04,940 --> 00:20:06,775 Peripheral nervous system are the nerves 335 00:20:06,775 --> 00:20:08,160 going to our skin and muscle. 336 00:20:11,550 --> 00:20:15,980 So the primary sensory neuron has the cell body outside. 337 00:20:15,980 --> 00:20:20,510 In primitive animals, it's in the surface epithelium. 338 00:20:20,510 --> 00:20:24,610 In us, it's in a ganglion near the central nervous system 339 00:20:24,610 --> 00:20:27,180 with a peripheral axon going out to the periphery. 340 00:20:30,320 --> 00:20:32,300 We have them in a little bit different shape 341 00:20:32,300 --> 00:20:34,745 for the skin of the body and for, say, 342 00:20:34,745 --> 00:20:38,310 the auditory or the olfactory system. 343 00:20:38,310 --> 00:20:41,185 But all these systems have a primary sensory neuron. 344 00:20:41,185 --> 00:20:42,780 What is a secondary sensory neuron? 345 00:20:42,780 --> 00:20:46,620 Well, the neuron that those neurons 346 00:20:46,620 --> 00:20:52,870 synapse with, or contact and transmit their activity to. 347 00:20:52,870 --> 00:20:54,330 They're in the central system. 348 00:20:54,330 --> 00:20:56,920 But they're the ones contacted. 349 00:20:56,920 --> 00:21:00,100 So we talk about the cochlear nuclei, for example. 350 00:21:00,100 --> 00:21:02,480 They get input from the auditory nerve. 351 00:21:06,090 --> 00:21:08,040 The trigeminal nuclei in the hindbrain 352 00:21:08,040 --> 00:21:10,220 getting input from the skin of the face. 353 00:21:13,550 --> 00:21:16,940 What's a motor neuron? 354 00:21:16,940 --> 00:21:20,450 Where is its cell body? 355 00:21:20,450 --> 00:21:26,118 Where's the cell body of a neuron innervating a muscle? 356 00:21:26,118 --> 00:21:27,492 AUDIENCE: I was going to say it's 357 00:21:27,492 --> 00:21:28,880 right on top of the muscle. 358 00:21:28,880 --> 00:21:29,960 PROFESSOR: No, it isn't. 359 00:21:29,960 --> 00:21:32,680 It's in the central nervous system. 360 00:21:32,680 --> 00:21:34,950 Any neuron in the central nervous system 361 00:21:34,950 --> 00:21:38,300 with a nerve fiber and axon leaving 362 00:21:38,300 --> 00:21:44,920 the central nervous system is a motor neuron. 363 00:21:44,920 --> 00:21:46,640 If it's an alpha motor neuron, it's 364 00:21:46,640 --> 00:21:49,570 contacting a striated muscle cell. 365 00:21:49,570 --> 00:21:52,020 So most of them are like that. 366 00:21:52,020 --> 00:21:54,900 But then there are also neurons like that that 367 00:21:54,900 --> 00:21:56,990 contact a cell in a ganglion. 368 00:21:56,990 --> 00:22:00,890 These are the autonomic nervous system cells. 369 00:22:00,890 --> 00:22:03,614 There you have a preganglonic motor neuron and then 370 00:22:03,614 --> 00:22:04,780 the ganglionic motor neuron. 371 00:22:08,550 --> 00:22:10,590 What are all the other neurons? 372 00:22:10,590 --> 00:22:13,250 We have the primary sensory, secondary sensory, 373 00:22:13,250 --> 00:22:14,420 and motor neuron. 374 00:22:14,420 --> 00:22:18,310 What are those enormous numbers of neurons in between? 375 00:22:18,310 --> 00:22:22,160 The general term is they're interneurons. 376 00:22:22,160 --> 00:22:25,620 But in the field of neuroanatomy, 377 00:22:25,620 --> 00:22:31,990 usually the interneuron is a short axon cell. 378 00:22:31,990 --> 00:22:35,950 But really, all the long axon cells and the short axon 379 00:22:35,950 --> 00:22:39,600 neurons are all interneurons. 380 00:22:39,600 --> 00:22:41,950 This is just a diagram that summarizes 381 00:22:41,950 --> 00:22:45,600 all those things I just told you. 382 00:22:45,600 --> 00:22:49,064 Some of you learn best if I describe it all verbally. 383 00:22:49,064 --> 00:22:50,730 Some of you have more trouble with that, 384 00:22:50,730 --> 00:22:52,938 but you see a picture like that and it's all obvious. 385 00:22:56,272 --> 00:22:59,310 In the left screen, the color's a lot better, 386 00:22:59,310 --> 00:23:04,820 because I used green to describe some of those cells 387 00:23:04,820 --> 00:23:07,290 where I've got pointers going to them. 388 00:23:07,290 --> 00:23:09,390 So there's the primary sensory neuron. 389 00:23:09,390 --> 00:23:12,390 You see where the cell body is there? 390 00:23:12,390 --> 00:23:14,280 Everything within those two lines 391 00:23:14,280 --> 00:23:18,510 is the central nervous system, like the spinal cord. 392 00:23:18,510 --> 00:23:20,242 But it could be in the brain, too. 393 00:23:20,242 --> 00:23:21,950 And there's the motor neuron with an axon 394 00:23:21,950 --> 00:23:23,150 going to a muscle cell. 395 00:23:26,380 --> 00:23:28,240 So I colored the motor neurons in. 396 00:23:28,240 --> 00:23:30,310 I've colored the primary sensory neuron. 397 00:23:30,310 --> 00:23:34,670 Secondary sensory neurons-- well in the book 398 00:23:34,670 --> 00:23:37,210 I'm writing I colored them green in the initial diagram, 399 00:23:37,210 --> 00:23:40,040 but I didn't color them green, here. 400 00:23:40,040 --> 00:23:41,300 All right. 401 00:23:41,300 --> 00:23:43,470 So one of the major specialization 402 00:23:43,470 --> 00:23:50,680 of neurons that govern how we sense, how we move, 403 00:23:50,680 --> 00:23:54,000 how we think-- everything. 404 00:23:54,000 --> 00:23:58,200 How are those cells different from other cells? 405 00:23:58,200 --> 00:24:00,680 How are they different from liver cells and kidney 406 00:24:00,680 --> 00:24:02,740 cells, and skin cells, and so forth? 407 00:24:02,740 --> 00:24:03,320 Yes. 408 00:24:03,320 --> 00:24:05,777 AUDIENCE: There are [INAUDIBLE] that transmit [INAUDIBLE]? 409 00:24:05,777 --> 00:24:06,360 PROFESSOR: OK. 410 00:24:06,360 --> 00:24:08,030 That's a big one. 411 00:24:08,030 --> 00:24:10,510 That's a specialization of a neuron. 412 00:24:10,510 --> 00:24:13,410 They can transmit what we call action potentials 413 00:24:13,410 --> 00:24:17,000 over long distances down axons, because the axon is 414 00:24:17,000 --> 00:24:26,030 a specialized property of the neuron membrane-- of the axon. 415 00:24:26,030 --> 00:24:28,740 They have many processes that don't transmit action 416 00:24:28,740 --> 00:24:33,360 potentials, but they still respond to input. 417 00:24:33,360 --> 00:24:36,400 So the general property here is this first one. 418 00:24:36,400 --> 00:24:37,880 We call it irritability. 419 00:24:37,880 --> 00:24:43,330 They respond to stimulation, and the response spreads. 420 00:24:46,110 --> 00:24:47,960 Even if it's not an action potential, 421 00:24:47,960 --> 00:24:50,860 you still get that spread. 422 00:24:50,860 --> 00:24:54,240 Well, if you could record from cells in a leaf, 423 00:24:54,240 --> 00:24:58,080 and you might find potentials across the membrane, 424 00:24:58,080 --> 00:25:00,900 and it might respond to stimulation and spread. 425 00:25:00,900 --> 00:25:04,140 But they're rarely like action potentials. 426 00:25:11,350 --> 00:25:15,160 So we call the response to a stimulus either mechanical 427 00:25:15,160 --> 00:25:21,110 or chemical that's being irritable or responsive 428 00:25:21,110 --> 00:25:24,170 to the outside world outside the cell. 429 00:25:24,170 --> 00:25:29,190 Conduction is that spread of potential 430 00:25:29,190 --> 00:25:34,240 where they have that extra specialization in the axon. 431 00:25:34,240 --> 00:25:37,350 It begins at a little place right near the cell body 432 00:25:37,350 --> 00:25:41,530 usually, near the beginning of the axon-- the axon hillock-- 433 00:25:41,530 --> 00:25:45,230 and the action that's where the action potential is initiated. 434 00:25:45,230 --> 00:25:47,490 How is it different from the other potentials? 435 00:25:47,490 --> 00:25:54,690 Well, once it's triggered, it goes all the way down the axon. 436 00:25:54,690 --> 00:25:56,800 Unless something unusual happens to block it, 437 00:25:56,800 --> 00:25:59,780 it goes all the way down to the axon endings. 438 00:25:59,780 --> 00:26:08,730 And there it can transmit its response to other cells 439 00:26:08,730 --> 00:26:11,820 at these contacts with other cells. 440 00:26:11,820 --> 00:26:15,220 We call those contacts synapses. 441 00:26:15,220 --> 00:26:17,780 Most of them are chemical synapses. 442 00:26:17,780 --> 00:26:20,610 And they cause a release of a chemical substance-- 443 00:26:20,610 --> 00:26:23,810 a neurotransmitter that affects the next cell. 444 00:26:23,810 --> 00:26:26,920 So these are the major specializations 445 00:26:26,920 --> 00:26:31,650 of nerve cells compared with any other cells in the body. 446 00:26:34,360 --> 00:26:39,050 So let's talk about some of the things 447 00:26:39,050 --> 00:26:42,590 these nervous system cells do. 448 00:26:42,590 --> 00:26:47,020 We'll talk about an example used by Scott in his book. 449 00:26:47,020 --> 00:26:48,920 He talks about the wandering spider. 450 00:26:48,920 --> 00:26:51,830 It's a spider that doesn't make a web, 451 00:26:51,830 --> 00:26:56,590 but it still hunts insect prey. 452 00:26:56,590 --> 00:26:58,990 How does it catch them without a web? 453 00:27:03,090 --> 00:27:06,790 It's got a lot of eyes, so you would 454 00:27:06,790 --> 00:27:09,760 think it's using its eyes. 455 00:27:09,760 --> 00:27:12,640 But you can blind them or block their eyes-- 456 00:27:12,640 --> 00:27:15,040 you can temporarily blind them just by covering 457 00:27:15,040 --> 00:27:22,230 their eyes with something-- and they still catch flies. 458 00:27:22,230 --> 00:27:25,140 How do they do it? 459 00:27:25,140 --> 00:27:26,033 Yes? 460 00:27:26,033 --> 00:27:29,320 AUDIENCE: Well, they have a lot of hairs on their legs. 461 00:27:29,320 --> 00:27:30,699 PROFESSOR: Little hairs, right? 462 00:27:30,699 --> 00:27:31,324 AUDIENCE: Yeah. 463 00:27:31,324 --> 00:27:39,620 They can detect small motions [INAUDIBLE] disturbances. 464 00:27:39,620 --> 00:27:43,100 PROFESSOR: Yeah, you're describing 465 00:27:43,100 --> 00:27:47,480 a pattern of disturbance in the air around a moving insect. 466 00:27:47,480 --> 00:27:49,830 Exactly. 467 00:27:49,830 --> 00:27:57,300 And this little spider has these little sensory hairs. 468 00:27:57,300 --> 00:28:00,960 Very interesting, because each hair, when it bends, 469 00:28:00,960 --> 00:28:04,430 there are at least four afferent sensory neurons-- 470 00:28:04,430 --> 00:28:08,450 they're called afferents-- sensory processes attached 471 00:28:08,450 --> 00:28:10,960 to that hair. 472 00:28:10,960 --> 00:28:14,260 So when the hair bends one way, one cell responds the most. 473 00:28:14,260 --> 00:28:16,150 It bends another way-- the opposite way-- 474 00:28:16,150 --> 00:28:17,920 another cell responds, and so forth. 475 00:28:17,920 --> 00:28:19,390 So in four different directions. 476 00:28:19,390 --> 00:28:24,330 And depending on its response, that one hair, 477 00:28:24,330 --> 00:28:30,170 you can tell basically where the direction of air current 478 00:28:30,170 --> 00:28:33,120 stimulating the hair. 479 00:28:33,120 --> 00:28:37,030 And it seems to be born with the ability 480 00:28:37,030 --> 00:28:42,730 to use the pattern of responses in all those hairs covering 481 00:28:42,730 --> 00:28:43,770 its body. 482 00:28:43,770 --> 00:28:47,630 And there's lots of them-- over 100. 483 00:28:47,630 --> 00:28:55,670 And it can actually leap into the air and grab insects. 484 00:28:55,670 --> 00:28:58,960 Up to 20 centimeters away they can detect things. 485 00:28:58,960 --> 00:29:01,120 And it can leap several centimeters. 486 00:29:01,120 --> 00:29:05,640 So it can tell when the insect's approaching, 487 00:29:05,640 --> 00:29:07,960 when it gets close-- it sort of times 488 00:29:07,960 --> 00:29:14,080 its leap when it's close enough, and it can catch the insect. 489 00:29:17,130 --> 00:29:18,040 Very interesting. 490 00:29:18,040 --> 00:29:19,570 He's got a nice description. 491 00:29:19,570 --> 00:29:21,550 There's a box covering two pages, there. 492 00:29:21,550 --> 00:29:24,450 And they even have some neurophysiological results 493 00:29:24,450 --> 00:29:28,260 where they're recording from some 494 00:29:28,260 --> 00:29:30,930 of the neurons responsive to those hairs. 495 00:29:34,834 --> 00:29:37,500 And of course, other kinds of spiders 496 00:29:37,500 --> 00:29:39,420 have other kinds of specializations. 497 00:29:39,420 --> 00:29:42,050 Usually they're responding to vibrations in the web 498 00:29:42,050 --> 00:29:44,830 when something is caught in their web. 499 00:29:44,830 --> 00:29:46,955 But these webless spiders have other means. 500 00:29:52,570 --> 00:29:56,820 So let's talk a little bit about the toad. 501 00:29:56,820 --> 00:30:00,850 Frogs and toads have a very specialized system 502 00:30:00,850 --> 00:30:02,480 for catching prey. 503 00:30:02,480 --> 00:30:06,580 They also catch insects, like that spider. 504 00:30:06,580 --> 00:30:09,845 But here the specializations are in its visual system. 505 00:30:13,890 --> 00:30:18,900 There are cells in the retina that are specifically tuned 506 00:30:18,900 --> 00:30:26,430 to respond to small, usually darker-- the little stimulus 507 00:30:26,430 --> 00:30:29,040 in the visual field darker than the rest of the field, 508 00:30:29,040 --> 00:30:33,310 like a fly or another small insect. 509 00:30:33,310 --> 00:30:36,850 And these cells respond best when 510 00:30:36,850 --> 00:30:39,900 a fly-like stimulus is moving. 511 00:30:39,900 --> 00:30:43,740 So just a little spot will stimulate those cells, 512 00:30:43,740 --> 00:30:44,980 as long as it's moving. 513 00:30:48,320 --> 00:30:50,400 Now those are in the retina. 514 00:30:50,400 --> 00:30:56,290 The retina's not enough to cause the frog to catch him. 515 00:30:56,290 --> 00:30:58,380 Where does the information go? 516 00:30:58,380 --> 00:31:00,710 Well, it goes down the optic nerve 517 00:31:00,710 --> 00:31:03,790 and to the opposite side of the roof of the midbrain, 518 00:31:03,790 --> 00:31:06,970 to the optic node of the midbrain. 519 00:31:06,970 --> 00:31:10,680 Or the optic tectum-- tectum just means "roof"-- 520 00:31:10,680 --> 00:31:14,493 the roof of the midbrain on the opposite side gets that input. 521 00:31:18,620 --> 00:31:21,810 And what do we know about the way 522 00:31:21,810 --> 00:31:29,360 the retina maps, senses fibers to the midbrain tectum? 523 00:31:29,360 --> 00:31:32,020 Well, we know it forms an organized map. 524 00:31:32,020 --> 00:31:34,320 So one part of the retina projects 525 00:31:34,320 --> 00:31:36,640 the one part of that optic lobe. 526 00:31:36,640 --> 00:31:39,100 Another part of the retina projects to another part. 527 00:31:39,100 --> 00:31:43,570 So it forms a map to the retina in the brain. 528 00:31:43,570 --> 00:31:48,100 We have that in our midbrain, too-- as well as 529 00:31:48,100 --> 00:31:51,300 other parts of our visual system. 530 00:31:51,300 --> 00:31:53,580 But in the frog, the dominant part 531 00:31:53,580 --> 00:31:58,210 by far-- and the only really important part for this prey 532 00:31:58,210 --> 00:32:00,210 catching-- is there in the midbrain. 533 00:32:09,340 --> 00:32:12,990 So what else do frogs and toads eat besides flies? 534 00:32:18,890 --> 00:32:23,172 Don't you ever have pet frogs and toads? 535 00:32:23,172 --> 00:32:23,840 AUDIENCE: Worms? 536 00:32:23,840 --> 00:32:24,621 PROFESSOR: Worms. 537 00:32:24,621 --> 00:32:25,120 Right. 538 00:32:25,120 --> 00:32:28,440 They love worms as much as they love flies. 539 00:32:28,440 --> 00:32:30,490 What characterizes a worm? 540 00:32:30,490 --> 00:32:36,350 Well, it's got to be moving and longer than it is wide. 541 00:32:36,350 --> 00:32:39,780 So if you make artificial stimuli 542 00:32:39,780 --> 00:32:41,420 and show them to the frog-- and this 543 00:32:41,420 --> 00:32:44,530 has been done by, say, placing the frog or the toad 544 00:32:44,530 --> 00:32:47,490 in the center of a turntable, and you put the stimuli 545 00:32:47,490 --> 00:32:50,440 on the platter, and you rotate it around, 546 00:32:50,440 --> 00:32:52,710 and you can put little black spots-- 547 00:32:52,710 --> 00:32:55,550 and you'll see that the frog keeps making these orienting 548 00:32:55,550 --> 00:32:58,050 movements towards it. 549 00:32:58,050 --> 00:33:01,750 Well, if you put in the elongated worm-like object, 550 00:33:01,750 --> 00:33:03,730 he does the same thing. 551 00:33:03,730 --> 00:33:06,460 And if you make it longer and longer, 552 00:33:06,460 --> 00:33:07,840 he responds more and more. 553 00:33:11,320 --> 00:33:12,820 What if you do the opposite? 554 00:33:12,820 --> 00:33:14,650 You make it wider and wider? 555 00:33:17,512 --> 00:33:21,680 He responds less and less. 556 00:33:21,680 --> 00:33:26,250 And if you start, say, with a square object, when it's little 557 00:33:26,250 --> 00:33:28,090 he does respond more and more. 558 00:33:28,090 --> 00:33:29,750 But then it reaches a certain size 559 00:33:29,750 --> 00:33:32,400 and it rapidly responds less and less. 560 00:33:32,400 --> 00:33:36,590 And it gets really big, and his whole response changes. 561 00:33:36,590 --> 00:33:38,580 He starts crouching. 562 00:33:38,580 --> 00:33:40,860 It starts being dangerous to him. 563 00:33:40,860 --> 00:33:42,710 These are all built-in responses-- 564 00:33:42,710 --> 00:33:45,800 innate responses-- of frogs and toads. 565 00:33:55,810 --> 00:33:57,960 So we've already talked about where 566 00:33:57,960 --> 00:34:00,930 in the central nervous system of a toad-- and then 567 00:34:00,930 --> 00:34:04,870 we could say the same thing about frogs-- 568 00:34:04,870 --> 00:34:07,790 that input from the retina is going. 569 00:34:07,790 --> 00:34:11,210 So here I'm asking, where in the central nervous system 570 00:34:11,210 --> 00:34:13,620 of a toad could electrical stimulus 571 00:34:13,620 --> 00:34:17,000 elicit a prey-catching, fixed-action pattern? 572 00:34:17,000 --> 00:34:20,090 Well, you could put an electrode in there. 573 00:34:20,090 --> 00:34:24,184 You anesthetize the frog, and implant the electrode. 574 00:34:24,184 --> 00:34:26,800 Let him wake up, recover from the surgery. 575 00:34:26,800 --> 00:34:29,820 Now just a little electrical stimulus 576 00:34:29,820 --> 00:34:34,449 in one part of that tectum-- that midbrain surface-- 577 00:34:34,449 --> 00:34:37,290 will elicit those turning movements 578 00:34:37,290 --> 00:34:39,570 that we were just talking about. 579 00:34:39,570 --> 00:34:41,804 So they can be elicited electrically. 580 00:34:45,340 --> 00:34:48,030 The only problem is when you elicit them electrically, 581 00:34:48,030 --> 00:34:49,489 he never follows through. 582 00:34:49,489 --> 00:34:51,030 What does a normal frog do? 583 00:34:51,030 --> 00:34:52,449 He's following the worm. 584 00:34:57,750 --> 00:35:01,290 Then what does he do to get it? 585 00:35:01,290 --> 00:35:02,735 Flips his tongue out. 586 00:35:02,735 --> 00:35:07,980 His tongue comes out like a dart. 587 00:35:07,980 --> 00:35:10,610 And the tongue is sticky at the end. 588 00:35:10,610 --> 00:35:13,360 So, splat! 589 00:35:13,360 --> 00:35:16,280 He gets it, pulls it back. 590 00:35:16,280 --> 00:35:17,630 Same for a fly. 591 00:35:17,630 --> 00:35:24,120 For the fly, he's tuned to wait until the fly alights. 592 00:35:24,120 --> 00:35:26,830 If it wasn't moving he will never try to get it. 593 00:35:26,830 --> 00:35:30,820 But if it was moving and stops, see 594 00:35:30,820 --> 00:35:33,000 the frog will just sit there and watch it move. 595 00:35:33,000 --> 00:35:35,770 But if it alights, then he'll get 596 00:35:35,770 --> 00:35:38,930 the prey-catching response-- if it's within range. 597 00:35:38,930 --> 00:35:42,170 He does have enough depth vision to know 598 00:35:42,170 --> 00:35:45,170 whether it's within range of his tongue. 599 00:35:45,170 --> 00:35:46,960 When you stimulate it electrically, 600 00:35:46,960 --> 00:35:49,771 you never get the tongue flick. 601 00:35:49,771 --> 00:35:50,270 Why? 602 00:35:52,930 --> 00:35:54,270 Give me a reason. 603 00:35:54,270 --> 00:35:57,760 I can stimulate repeatedly. 604 00:35:57,760 --> 00:36:00,460 I can stimulate the turning movements. 605 00:36:00,460 --> 00:36:03,220 He keeps reorienting to different positions 606 00:36:03,220 --> 00:36:06,320 in the field every time I stimulate them. 607 00:36:06,320 --> 00:36:09,680 Why does he never flip his tongue? 608 00:36:09,680 --> 00:36:13,380 Isn't that all built-in? 609 00:36:13,380 --> 00:36:16,820 Isn't it part of the same fixed-action pattern? 610 00:36:16,820 --> 00:36:18,760 Well normally, yes. 611 00:36:18,760 --> 00:36:20,580 Because normally, of course, just think. 612 00:36:23,850 --> 00:36:25,485 This is a frog without an electrode. 613 00:36:25,485 --> 00:36:28,050 He turns. 614 00:36:28,050 --> 00:36:32,600 That stimulus is moving across his tectum. 615 00:36:32,600 --> 00:36:37,280 He always brings it so the stimulus is in front of him. 616 00:36:37,280 --> 00:36:39,440 So he's aligned. 617 00:36:39,440 --> 00:36:41,410 So he can make the tongue flick response. 618 00:36:41,410 --> 00:36:45,490 Now it's always up in the front of the tectum. 619 00:36:45,490 --> 00:36:49,000 That's the part of the tectum which, if you stimulate, 620 00:36:49,000 --> 00:36:52,680 you can also get the tongue flick. 621 00:36:52,680 --> 00:36:55,290 But with just one electrode in the middle of the tectum, 622 00:36:55,290 --> 00:36:57,860 you'll never get it, because we can't 623 00:36:57,860 --> 00:36:59,600 imitate with a fixed electrode. 624 00:36:59,600 --> 00:37:06,004 We can't imitate the whole normal stimulus sequence. 625 00:37:06,004 --> 00:37:07,420 Then here I say, what would change 626 00:37:07,420 --> 00:37:11,100 if an electrode were moved a short distance? 627 00:37:11,100 --> 00:37:13,400 Well, he would just change the position 628 00:37:13,400 --> 00:37:15,287 he's orienting towards. 629 00:37:15,287 --> 00:37:17,120 So you put it way in the back of the tectum, 630 00:37:17,120 --> 00:37:20,604 he would make these bigger orienting moves. 631 00:37:20,604 --> 00:37:22,020 If you put it closer to the front, 632 00:37:22,020 --> 00:37:25,250 he makes short orienting movements. 633 00:37:25,250 --> 00:37:29,975 If you place it closer to the midline, he orients upward. 634 00:37:29,975 --> 00:37:32,300 If you place it further out laterally, 635 00:37:32,300 --> 00:37:37,030 he orients to the side and downward. 636 00:37:37,030 --> 00:37:41,470 Well, the map we have of the retina in our midbrain 637 00:37:41,470 --> 00:37:44,960 is the same as the map in the frog. 638 00:37:44,960 --> 00:37:49,250 It's conserved across all the vertebrates. 639 00:37:49,250 --> 00:37:54,570 The relative size of structures changes a lot, 640 00:37:54,570 --> 00:37:57,400 but the existence of these structures 641 00:37:57,400 --> 00:37:59,670 is the same throughout the vertebrates. 642 00:37:59,670 --> 00:38:03,510 And that's true for all the structures of the spinal cord 643 00:38:03,510 --> 00:38:06,115 and brain stem that control these fixed-action patterns. 644 00:38:09,010 --> 00:38:10,600 Another concept here. 645 00:38:10,600 --> 00:38:13,155 We talked about what a motor neuron is. 646 00:38:13,155 --> 00:38:14,930 If the motor neuron's stimulated, 647 00:38:14,930 --> 00:38:16,610 you get a muscle twitch. 648 00:38:19,161 --> 00:38:21,740 If a group of motor neurons are stimulated, 649 00:38:21,740 --> 00:38:23,910 you can get more movement. 650 00:38:23,910 --> 00:38:27,710 And if I stimulate all the motor neurons in the cord, 651 00:38:27,710 --> 00:38:30,810 I can get suddenly rigidity if I'm stimulating, 652 00:38:30,810 --> 00:38:33,205 say, in the motor neurons controlling my hand. 653 00:38:33,205 --> 00:38:35,290 But if I'm stimulating just one group of them 654 00:38:35,290 --> 00:38:37,155 I can get flexion of the hand. 655 00:38:37,155 --> 00:38:41,670 I stimulate another group, I can get-- this would be extension, 656 00:38:41,670 --> 00:38:43,980 this would be flexion. 657 00:38:43,980 --> 00:38:46,060 So I could elicit grasping. 658 00:38:46,060 --> 00:38:50,450 What about a command neuron? 659 00:38:50,450 --> 00:38:53,170 It has a different meaning, also very 660 00:38:53,170 --> 00:38:57,430 important in studying the control of these movements 661 00:38:57,430 --> 00:38:59,660 in fixed-action patterns. 662 00:38:59,660 --> 00:39:01,383 What is a command neuron? 663 00:39:05,820 --> 00:39:12,250 It's a term used in neuroethology 664 00:39:12,250 --> 00:39:16,000 to describe a neuron that you can identify. 665 00:39:16,000 --> 00:39:16,950 Usually it's a neuron. 666 00:39:16,950 --> 00:39:21,230 You can identify the same neuron in one member of the species 667 00:39:21,230 --> 00:39:22,237 to another. 668 00:39:22,237 --> 00:39:24,320 Sometimes they even have different color pigments. 669 00:39:28,030 --> 00:39:31,220 It's a neuron where if you stimulate that one 670 00:39:31,220 --> 00:39:35,120 neuron you stimulate a whole pattern of movement. 671 00:39:35,120 --> 00:39:38,760 You get a behavior from one neuron. 672 00:39:38,760 --> 00:39:42,630 You stimulate a command neuron in a crayfish, you can elicit, 673 00:39:42,630 --> 00:39:45,910 if you're in the right place, you stimulate the right command 674 00:39:45,910 --> 00:39:48,390 neuron, you can get a tail-flip response. 675 00:39:48,390 --> 00:39:52,375 The animal will escape as if escaping from a predator. 676 00:39:56,460 --> 00:40:01,500 Mammals and vertebrates in general-- 677 00:40:01,500 --> 00:40:04,720 it's harder to find the command neuron. 678 00:40:04,720 --> 00:40:06,765 There are a few very large neurons 679 00:40:06,765 --> 00:40:11,373 that you can identify, say, across fish and amphibians. 680 00:40:14,212 --> 00:40:16,660 There's very giant cells in the hindbrain 681 00:40:16,660 --> 00:40:18,440 they call the Mauthner cells that 682 00:40:18,440 --> 00:40:21,580 can elicit rapid escape responses. 683 00:40:21,580 --> 00:40:23,220 They're like command neurons. 684 00:40:23,220 --> 00:40:25,820 But otherwise, usually these are insects 685 00:40:25,820 --> 00:40:27,155 and other invertebrates. 686 00:40:33,130 --> 00:40:33,630 All right. 687 00:40:33,630 --> 00:40:36,270 That's the difference between a command neuron and a motor 688 00:40:36,270 --> 00:40:36,770 neuron. 689 00:40:36,770 --> 00:40:40,170 In a vertebrate you have groups of neurons 690 00:40:40,170 --> 00:40:44,190 though that act as command groups of neurons, which 691 00:40:44,190 --> 00:40:50,290 when stimulated can elicit a whole sequence of movements-- 692 00:40:50,290 --> 00:40:54,100 for example, in the caudal part of the midbrain. 693 00:40:54,100 --> 00:40:57,310 Below the optic tectum-- below in fact 694 00:40:57,310 --> 00:41:00,490 the auditory tectum-- it's in the caudal midbrain-- 695 00:41:00,490 --> 00:41:04,650 there's an area there which, when activated, 696 00:41:04,650 --> 00:41:07,560 elicits locomotion. 697 00:41:07,560 --> 00:41:11,241 You get the right place and you stimulate 698 00:41:11,241 --> 00:41:15,780 with enough activation, you can get rapid running movements. 699 00:41:15,780 --> 00:41:19,160 There are similar groups of neurons 700 00:41:19,160 --> 00:41:23,890 further forward in an area we call the subthalamus. 701 00:41:23,890 --> 00:41:26,590 Parts of the subthalamus get direct visual input 702 00:41:26,590 --> 00:41:29,800 from the retina. 703 00:41:29,800 --> 00:41:35,630 And more immediately, they can activate these neurons 704 00:41:35,630 --> 00:41:38,950 that seem to connect directly to that midbrain center, 705 00:41:38,950 --> 00:41:43,360 because they also elicit rapid running movements usually 706 00:41:43,360 --> 00:41:45,240 involved in escape behavior. 707 00:41:45,240 --> 00:41:48,310 That's a kind of command neuron group. 708 00:41:48,310 --> 00:41:51,380 It's just that we can't identify the single neuron. 709 00:41:51,380 --> 00:41:53,890 So if I say "command neuron," I'm 710 00:41:53,890 --> 00:42:00,080 almost always talking about invertebrate animals 711 00:42:00,080 --> 00:42:04,850 where we can actually identify the same cell from animal 712 00:42:04,850 --> 00:42:05,500 to animal. 713 00:42:08,770 --> 00:42:13,660 So let's talk about the giant axon. 714 00:42:13,660 --> 00:42:16,645 What is the main advantage of the giant axon 715 00:42:16,645 --> 00:42:20,150 in the triggering of an escape response? 716 00:42:20,150 --> 00:42:23,820 You see giant axons in squid. 717 00:42:23,820 --> 00:42:28,810 It was the discovery of giant axons in squid 718 00:42:28,810 --> 00:42:35,220 that led to the detailed physiology of the action 719 00:42:35,220 --> 00:42:38,480 potential for the first time. 720 00:42:38,480 --> 00:42:46,070 Because this was before microelectrodes were perfected. 721 00:42:46,070 --> 00:42:49,960 They could get a tiny wire inside that giant axon. 722 00:42:49,960 --> 00:42:55,070 They were up to one millimeter in diameter in a squid. 723 00:42:55,070 --> 00:42:59,260 So it enabled detailed study of the physiology of the action 724 00:42:59,260 --> 00:43:02,475 potential in the giant axon. 725 00:43:02,475 --> 00:43:06,110 But why would the squid have giant axons? 726 00:43:06,110 --> 00:43:07,970 They use a lot of energy. 727 00:43:07,970 --> 00:43:10,555 If all their axons were like that, 728 00:43:10,555 --> 00:43:14,470 they'd be gigantic animals. 729 00:43:14,470 --> 00:43:18,330 Some of them are pretty large, but they're not gigantic. 730 00:43:18,330 --> 00:43:20,506 And some of them are small, too, but all of them 731 00:43:20,506 --> 00:43:21,840 have these giant axons. 732 00:43:21,840 --> 00:43:24,210 Why? 733 00:43:24,210 --> 00:43:31,142 What's the advantage of making an axon larger in diameter? 734 00:43:31,142 --> 00:43:32,850 AUDIENCE: They have more rapid responses? 735 00:43:32,850 --> 00:43:35,090 PROFESSOR: Yeah, one word-- speed. 736 00:43:35,090 --> 00:43:36,155 Rapid conduction. 737 00:43:40,360 --> 00:43:44,650 That's why giant axons evolved. 738 00:43:44,650 --> 00:43:48,330 Because axonal conduction speed depends 739 00:43:48,330 --> 00:43:54,670 first of all on the diameter of the axon. 740 00:43:54,670 --> 00:43:57,415 So you get faster conduction of the action potential. 741 00:44:00,890 --> 00:44:03,560 Well, we have rapid conduction too, 742 00:44:03,560 --> 00:44:05,690 and we don't have giant axons. 743 00:44:05,690 --> 00:44:08,230 We do have some axons larger than others, 744 00:44:08,230 --> 00:44:10,860 and they do conduct more rapidly, 745 00:44:10,860 --> 00:44:14,700 but they're nowhere near the size of the squid. 746 00:44:14,700 --> 00:44:19,920 And yet we get conduction that's just as fast as in the squid-- 747 00:44:19,920 --> 00:44:21,770 probably faster. 748 00:44:21,770 --> 00:44:26,360 I can't remember the exact speed of conduction in a giant axon, 749 00:44:26,360 --> 00:44:31,330 but I know the long axons down to our spinal cord 750 00:44:31,330 --> 00:44:34,350 are very rapidly conducting. 751 00:44:34,350 --> 00:44:39,293 The reason is the evolution of the myelin sheath. 752 00:44:42,240 --> 00:44:48,300 Myelin is when the axon is wrapped round and round 753 00:44:48,300 --> 00:44:52,550 by the membrane of a glial cell that sort of insulates 754 00:44:52,550 --> 00:44:58,370 the axon from the ionic potentials that normally are 755 00:44:58,370 --> 00:45:00,810 involved in the action potential. 756 00:45:00,810 --> 00:45:03,590 Well, if you insulated the whole axon like that, 757 00:45:03,590 --> 00:45:07,930 you wouldn't get any action potentials at all. 758 00:45:07,930 --> 00:45:11,700 So this is why it gets-- first of all, 759 00:45:11,700 --> 00:45:17,085 deal with the rate of spread of current down an axon. 760 00:45:17,085 --> 00:45:21,570 For all you engineers, this should make sense to you. 761 00:45:21,570 --> 00:45:24,930 If you're not engineers, well, be patient. 762 00:45:24,930 --> 00:45:28,820 You've studied basic physics and math. 763 00:45:28,820 --> 00:45:31,930 The rate of passive spread of current 764 00:45:31,930 --> 00:45:38,110 down the center of an axon is proportional to the reciprocal 765 00:45:38,110 --> 00:45:38,875 of this product. 766 00:45:46,390 --> 00:45:50,030 The resistance of the axon down the cylinder 767 00:45:50,030 --> 00:45:55,260 can be measured, and the capacitance of the membrane. 768 00:45:55,260 --> 00:45:59,680 You can increase the capacitance with myelin. 769 00:45:59,680 --> 00:46:02,780 You can decrease the resistance simply 770 00:46:02,780 --> 00:46:04,615 by making the axon bigger around. 771 00:46:09,210 --> 00:46:13,850 I point out down here that the resistance decreases 772 00:46:13,850 --> 00:46:17,760 in proportion to the square of the diameter of the axon, 773 00:46:17,760 --> 00:46:22,860 and the capacitance increases in proportion to the diameter. 774 00:46:22,860 --> 00:46:25,510 So then how does the action potential move? 775 00:46:25,510 --> 00:46:31,100 We know that the myelin makes that passive conduction 776 00:46:31,100 --> 00:46:34,000 the passive spread of current-- the kind of spread 777 00:46:34,000 --> 00:46:37,240 you get in the cell body where you touch the cell in one 778 00:46:37,240 --> 00:46:39,010 place-- you stimulate it in one place-- 779 00:46:39,010 --> 00:46:42,270 it does spread to the rest of the cell. 780 00:46:42,270 --> 00:46:44,130 But not if it's not an action potential. 781 00:46:44,130 --> 00:46:45,640 In fact, it gets detrimental. 782 00:46:45,640 --> 00:46:48,660 It gets weaker the further you get from where you stimulate. 783 00:46:48,660 --> 00:46:52,420 The same is true in all those little processes of the cell 784 00:46:52,420 --> 00:46:53,991 we called dendrites. 785 00:46:53,991 --> 00:46:54,865 It spreads passively. 786 00:47:00,290 --> 00:47:05,120 Here's a greatly enlarged axon-- this long cylinder. 787 00:47:05,120 --> 00:47:07,790 That's the axon membrane. 788 00:47:07,790 --> 00:47:15,140 The way the myelin forms is-- let's say 789 00:47:15,140 --> 00:47:17,515 this is a peripheral axon in our leg. 790 00:47:21,370 --> 00:47:24,800 We'll draw the cell body forming that. 791 00:47:24,800 --> 00:47:26,670 Here's the nucleus. 792 00:47:26,670 --> 00:47:31,830 That cell, its membrane is wrapped round and round 793 00:47:31,830 --> 00:47:33,800 and around this portion of the axon. 794 00:47:33,800 --> 00:47:36,750 This is a cross-section. 795 00:47:36,750 --> 00:47:39,670 And then there's another cell wrapping its membrane here. 796 00:47:39,670 --> 00:47:42,350 Another one here wrapping its membrane. 797 00:47:42,350 --> 00:47:43,892 These cells are called Schwann cells. 798 00:47:43,892 --> 00:47:44,933 They're in the periphery. 799 00:47:44,933 --> 00:47:47,310 If this was in the central nervous system, in the brain, 800 00:47:47,310 --> 00:47:50,180 say, where we also have a lot of myelin, 801 00:47:50,180 --> 00:47:52,210 same in the spinal cord-- then there 802 00:47:52,210 --> 00:48:02,840 would be a cell up here forming myelin, and like this. 803 00:48:02,840 --> 00:48:14,680 And it would have these branches spreading down and wrapping 804 00:48:14,680 --> 00:48:21,270 the membrane round and round and around the axon. 805 00:48:21,270 --> 00:48:23,395 So the same cell here can myelinate 806 00:48:23,395 --> 00:48:27,350 a whole bunch of axons. 807 00:48:27,350 --> 00:48:29,395 That's an [INAUDIBLE] site in the brain. 808 00:48:29,395 --> 00:48:31,570 So the same thing is accomplished. 809 00:48:31,570 --> 00:48:36,470 These cells are insulating the axon. 810 00:48:36,470 --> 00:48:40,210 So how does that help? 811 00:48:40,210 --> 00:48:48,830 If the action potential, say, is triggered here, 812 00:48:48,830 --> 00:48:54,890 we know that this depolarization of the membrane 813 00:48:54,890 --> 00:48:59,330 spreads very fast down the axon. 814 00:49:01,900 --> 00:49:05,390 No action potential until you get to the next node 815 00:49:05,390 --> 00:49:07,780 here, where there's no myelin. 816 00:49:07,780 --> 00:49:10,620 It triggers an action potential there. 817 00:49:10,620 --> 00:49:15,470 Then that spreads decrementally down to the next node. 818 00:49:15,470 --> 00:49:19,660 The spread is extremely rapid with a large diameter 819 00:49:19,660 --> 00:49:21,930 and with the insulated membrane. 820 00:49:21,930 --> 00:49:24,230 It keeps triggering the action potential in node 821 00:49:24,230 --> 00:49:28,150 after node after node-- that's called saltatory conduction-- 822 00:49:28,150 --> 00:49:30,100 jumping conduction. 823 00:49:30,100 --> 00:49:33,000 And it just goes b-r-r-a-p! 824 00:49:33,000 --> 00:49:36,090 And it goes very, very fast without making 825 00:49:36,090 --> 00:49:38,680 the axon so gigantic. 826 00:49:38,680 --> 00:49:41,770 So that's how it happens. 827 00:49:41,770 --> 00:49:45,660 And that's the end of the class. 828 00:49:45,660 --> 00:49:51,450 And we'll talk about motivational states next time.