WEBVTT 00:00:00.000 --> 00:00:03.319 This is going to be... Let me clear everything 00:00:03.319 --> 00:00:06.759 out. I don't know why. This is going to be visual 00:00:06.759 --> 00:00:10.320 inputs but only the retina to the superior colliculus 00:00:10.320 --> 00:00:15.679 because only the mesencephalon. Remember the 00:00:15.679 --> 00:00:18.500 three issues that I have with the mesencephalon 00:00:18.500 --> 00:00:22.019 with the autistic phenotype. Eye movements because 00:00:22.019 --> 00:00:25.260 of the superior colliculus. This is a fast relay 00:00:25.260 --> 00:00:29.850 station and hearing, audit, audition. which is 00:00:29.850 --> 00:00:35.170 the inferior colliculus remember auditory brainstem 00:00:35.170 --> 00:00:39.409 response wave five which is the last wave up 00:00:39.409 --> 00:00:44.149 until it gets hearing gets into the subcortical 00:00:44.149 --> 00:00:48.210 areas like the thalamus and so forth and then 00:00:48.210 --> 00:00:51.969 motor movements with the basal ganglia we'll 00:00:51.969 --> 00:00:54.310 touch a little bit about the basal ganglia here 00:00:54.310 --> 00:00:57.530 because of the superior colliculus projecting 00:00:57.530 --> 00:01:04.560 to the basal ganglia for motor movements. So 00:01:04.560 --> 00:01:10.540 this is the same kind of diagram cartoon, if 00:01:10.540 --> 00:01:18.480 you will, from the auditory brainstem response 00:01:18.480 --> 00:01:23.200 episode, the whiteboard. So the green is the 00:01:23.200 --> 00:01:25.519 inferior colliculus, which is in the mesencephalon. 00:01:26.540 --> 00:01:29.599 The red is the superior colliculus, which is 00:01:29.599 --> 00:01:33.579 this, right here. And then this is the thalamus, 00:01:33.819 --> 00:01:37.340 okay, both. So contralateral, which means both 00:01:37.340 --> 00:01:41.099 sides. These little humps are the medial, geniculate. 00:01:41.180 --> 00:01:44.640 And then the lateral geniculate, medial is in 00:01:44.640 --> 00:01:47.920 the middle, lateral is on the outside. This is 00:01:47.920 --> 00:01:53.280 vision. This is vision. And this is auditory, 00:01:53.459 --> 00:01:57.349 here. Remember in the Autism and Eye Movements 00:01:57.349 --> 00:02:00.450 episode, I said that these things are spatially 00:02:00.450 --> 00:02:04.230 close. They can just reach out and high -five 00:02:04.230 --> 00:02:09.509 each other. It's for fast transmission. So, if 00:02:09.509 --> 00:02:14.050 we think about the retina, okay? I always like 00:02:14.050 --> 00:02:16.949 to draw the retina thick and dark because of 00:02:16.949 --> 00:02:21.810 the melanin. And then we have the pupil, okay? 00:02:22.110 --> 00:02:24.830 This is just... the eye right here pretty good 00:02:24.830 --> 00:02:30.530 it's a pretty good eye and then there's a monosynaptic 00:02:30.530 --> 00:02:36.469 connection not only to the thalamus here the 00:02:36.469 --> 00:02:39.849 lateral geniculate which is here it's just a 00:02:39.849 --> 00:02:44.710 different angle and the medial but of course 00:02:44.710 --> 00:02:49.349 the retina projects to the thalamus monosynaptically 00:02:49.349 --> 00:02:53.460 you know one connection but also to the superior 00:02:53.460 --> 00:02:58.120 colliculus which is like this you're just like 00:02:58.120 --> 00:03:02.639 a noodle if this was the mesencephalon okay and 00:03:02.639 --> 00:03:05.259 then this is just kind of like the pons the brain 00:03:05.259 --> 00:03:09.800 stem okay sometimes i draw this connection to 00:03:09.800 --> 00:03:12.379 the lateral geniculate which is the relay station 00:03:12.379 --> 00:03:18.460 for all vision two i want to do green for the 00:03:18.460 --> 00:03:22.349 projections two lateral geniculate to the superior 00:03:22.349 --> 00:03:26.370 caliculus, which is right here. I might as well 00:03:26.370 --> 00:03:28.389 color coat these. The red's got black. Is it 00:03:28.389 --> 00:03:31.870 showing up red? Not really. Okay, I gotta work 00:03:31.870 --> 00:03:35.810 on this. And then the inferior caliculus, okay? 00:03:35.969 --> 00:03:41.129 But there's about 15 % of nerve fibers that go 00:03:41.129 --> 00:03:43.889 directly to the superior caliculus, okay? This 00:03:43.889 --> 00:03:47.409 is for fast acting visual responses, okay? So 00:03:47.409 --> 00:03:51.439 we can orient our gaze and orient our head movements 00:03:51.439 --> 00:03:54.000 okay because we're going to get into some of 00:03:54.000 --> 00:03:58.439 these descending fibers so about 15 percent are 00:03:58.439 --> 00:04:01.439 retina to superior colliculus of the total fibers 00:04:01.439 --> 00:04:04.479 which is still millions of fibers okay the rest 00:04:04.479 --> 00:04:07.800 of them go to the lateral geniculate all right 00:04:07.800 --> 00:04:13.840 so some of these fibers from the superior colliculus 00:04:13.840 --> 00:04:18.439 five minutes already are descending Okay, so 00:04:18.439 --> 00:04:21.220 they go down here to the to the rest of the brain 00:04:21.220 --> 00:04:25.300 stem some of these are cranial nerves three four 00:04:25.300 --> 00:04:28.959 and six specifically cranial nerve three and 00:04:28.959 --> 00:04:32.759 four are within the mesencephalon ocular motor 00:04:32.759 --> 00:04:36.959 and tracheal cranial nerve, okay, this is for 00:04:36.959 --> 00:04:42.279 eye movements and then Cranial nerve six is down 00:04:42.279 --> 00:04:46.410 below the mesencephalon a bit which is abducens. 00:04:46.449 --> 00:04:48.870 If you know anything about the cranial nerves, 00:04:49.949 --> 00:04:53.050 cranial nerve six is the easy one, abducens. 00:04:53.389 --> 00:04:56.689 It's because the eyes are independent structures, 00:04:56.689 --> 00:05:02.029 but they orient identically. Like their movements 00:05:02.029 --> 00:05:06.250 are identical, you know, however the eyes are 00:05:06.250 --> 00:05:13.009 doing. It's just, that's cranial nerve six. And 00:05:13.009 --> 00:05:16.970 then The superior colliculus will also touch 00:05:16.970 --> 00:05:22.949 9, 10, 11, and 12 as well to help orient the 00:05:22.949 --> 00:05:28.129 head towards wherever we want to send our vision 00:05:28.129 --> 00:05:33.230 or visual inputs. Now 10 is the easy one. The 00:05:33.230 --> 00:05:36.449 vagus nerve, that's the big one. So this is the 00:05:36.449 --> 00:05:39.810 thalamus. Now that I think about it, I don't 00:05:39.810 --> 00:05:42.949 know if we ever drew out the thalamus like we 00:05:42.949 --> 00:05:47.069 should. Probably. Because we talk about it a 00:05:47.069 --> 00:05:50.269 lot. We talk about the thalamic reticular nucleus, 00:05:50.589 --> 00:05:56.370 TRN, the shell that kind of protects the thalamus 00:05:56.370 --> 00:05:59.089 here. Thalamus is pretty big. It's a workhorse. 00:05:59.889 --> 00:06:02.790 If we would just draw the thalamus out here, 00:06:03.029 --> 00:06:07.069 let's just say it's like this angle, medial geniculate 00:06:07.069 --> 00:06:10.990 right here, and then the lateral geniculate. 00:06:11.199 --> 00:06:14.959 right here okay if we were going to draw and 00:06:14.959 --> 00:06:17.579 just imagine this is cut out okay this is just 00:06:17.579 --> 00:06:21.240 like a shell okay this is let's just say this 00:06:21.240 --> 00:06:25.920 is the trn this is protecting the thalamus let's 00:06:25.920 --> 00:06:28.139 just say this is the rest of the thalamus but 00:06:28.139 --> 00:06:33.980 it's just cut out and there's a strong nuclei 00:06:33.980 --> 00:06:37.560 here called pulvin here which is uh receiving 00:06:37.560 --> 00:06:41.060 a lot of sensory inputs okay and The thalamus 00:06:41.060 --> 00:06:46.579 has a lot of little subdivisions. Okay, so this 00:06:46.579 --> 00:06:51.579 shell is all inhibition. Remember the thalamic 00:06:51.579 --> 00:06:55.579 reticular nucleus inhibitory neurons and autism 00:06:55.579 --> 00:06:59.120 episode, all about inhibition. A lot of parvalbium 00:06:59.120 --> 00:07:04.339 here and somatostatin, which are kind of the 00:07:04.339 --> 00:07:08.589 top two inhibition neurons. Parvoalbum interneuron 00:07:08.589 --> 00:07:12.110 is fast acting, GABA -A a lot, and some GABA 00:07:12.110 --> 00:07:15.310 -C. And then somatostatin is more slower acting, 00:07:16.189 --> 00:07:20.550 GABA -B. So GABA -A is anywhere from like 2 to 00:07:20.550 --> 00:07:24.870 10 milliseconds of activation. GABA -B is 10 00:07:24.870 --> 00:07:29.529 to 50 milliseconds, so it's kind of delayed. 00:07:30.410 --> 00:07:34.209 Okay, so this thalamus here, I guess we could 00:07:34.209 --> 00:07:37.290 draw it out here too. has a shell over it it's 00:07:37.290 --> 00:07:41.069 like a security guard okay if you if you're looking 00:07:41.069 --> 00:07:44.189 at this from the overhead view this view right 00:07:44.189 --> 00:07:47.750 here it's just kind of like from the posterior 00:07:47.750 --> 00:07:51.990 but kind of angled it's kind of angled down just 00:07:51.990 --> 00:07:54.569 so we can see it but if you're going directly 00:07:54.569 --> 00:07:58.170 overhead looking at it like this you can say 00:07:58.170 --> 00:08:00.509 that the thalamus it's kind of like two eggs 00:08:00.509 --> 00:08:04.560 or something like this the thalamic reticular 00:08:04.560 --> 00:08:11.959 nucleus is on the outside. This prevents unwanted 00:08:11.959 --> 00:08:16.019 projections coming in because the thalamus receives 00:08:16.019 --> 00:08:21.220 all sensory information at least the thalamic 00:08:21.220 --> 00:08:24.399 reticular nucleus does and this will filter out 00:08:24.399 --> 00:08:28.420 what can enter because the thalamus is a workhorse 00:08:28.420 --> 00:08:33.700 okay so all sensations Okay, for instance, vision, 00:08:34.440 --> 00:08:39.519 the lateral geniculate here or here, the auditory 00:08:39.519 --> 00:08:44.299 auditory comes more this way from the ears, of 00:08:44.299 --> 00:08:49.580 course, and then in inward to the brainstem and 00:08:49.580 --> 00:08:53.240 then up. Okay, and then like mechanical receptors, 00:08:53.620 --> 00:08:59.320 mechanical receptors, touch from the peripheral. 00:08:59.870 --> 00:09:03.009 will come in through the spine and up the brain 00:09:03.009 --> 00:09:08.490 stem and into the thalamus like this. Okay? So 00:09:08.490 --> 00:09:11.870 I guess back to the superior colliculus but here's 00:09:11.870 --> 00:09:14.990 um since we haven't really discussed the thalamus 00:09:14.990 --> 00:09:19.269 in detail not uh we haven't really visualized 00:09:19.269 --> 00:09:24.210 it okay so this shell right here is very protective 00:09:24.210 --> 00:09:29.950 with good measure too good it's it's needed Just 00:09:29.950 --> 00:09:33.750 imagine sensing or perceiving all senses coming 00:09:33.750 --> 00:09:38.190 in. It would be wild. It's almost like schizophrenia 00:09:38.190 --> 00:09:44.649 does this with the delusions. They can't discriminate 00:09:44.649 --> 00:09:50.370 all the senses. And, you know, autism is very 00:09:50.370 --> 00:09:55.929 close, very close to schizophrenia. So the superior 00:09:55.929 --> 00:10:00.269 colliculus here, it receives about 15 % of the 00:10:00.269 --> 00:10:03.350 vision nerve fibers directly. So what are some 00:10:03.350 --> 00:10:11.149 of the outputs? Let's just say the superior colliculus 00:10:11.149 --> 00:10:14.370 receives some visual information. What happens 00:10:14.370 --> 00:10:19.450 next? Okay, there's a little crosstalk that it 00:10:19.450 --> 00:10:22.190 will speak within itself, and this happens fast 00:10:22.190 --> 00:10:25.860 for autism. compared to typicals. The inputs 00:10:25.860 --> 00:10:30.879 going across and enter superior colliculus and 00:10:30.879 --> 00:10:36.399 even from side to side, contralateral. With autism, 00:10:36.580 --> 00:10:40.799 it's fast, much faster than typicals. But one 00:10:40.799 --> 00:10:44.080 of the key areas that I've talked about, and 00:10:44.080 --> 00:10:47.500 it will be up here, the frontal eye fields. We 00:10:47.500 --> 00:10:52.279 have like a supplementary frontal eye fields 00:10:52.279 --> 00:10:56.620 up here and then I should just maybe write F 00:10:56.620 --> 00:11:02.259 E F F E F for frontal eye fields this is right 00:11:02.259 --> 00:11:07.899 in here so vision superior colliculus and um 00:11:07.899 --> 00:11:11.899 deep inside the brain deep inside right in the 00:11:11.899 --> 00:11:14.100 middle all the way back up to the frontal eye 00:11:14.100 --> 00:11:18.779 fields however it will hit the thalamus first 00:11:19.000 --> 00:11:21.419 This isn't superior colliculus to frontal eye 00:11:21.419 --> 00:11:24.500 fields of monosynaptic connection. Okay, sometimes 00:11:24.500 --> 00:11:28.259 I draw it out as such, but here in the thalamus 00:11:28.259 --> 00:11:31.440 is the pulmonary that I mentioned. And then there 00:11:31.440 --> 00:11:35.519 is this track up here. You could say that it's 00:11:35.519 --> 00:11:40.879 here. So pulmonary here is also here. And then 00:11:40.879 --> 00:11:46.019 the medial, medial dorsal, MD thalamus, MD thalamus, 00:11:46.139 --> 00:11:50.940 medial dorsal. And this is also here. So here. 00:11:51.980 --> 00:11:55.159 So, retina to the superior colliculus, superior 00:11:55.159 --> 00:11:59.320 colliculus to the pulmonary, pulmonary to the 00:11:59.320 --> 00:12:02.139 medial dorsal, to the fertile eye fields. And 00:12:02.139 --> 00:12:05.860 this is a fast -acting connection here with the 00:12:05.860 --> 00:12:11.019 autistic phenotype because the relay of stimuli 00:12:11.019 --> 00:12:14.779 into this superior colliculus and out of it is 00:12:14.779 --> 00:12:19.870 really fast for autism. Okay. And this is a big 00:12:19.870 --> 00:12:23.990 connection. So we'll go all the way up to here. 00:12:24.190 --> 00:12:27.090 The frontal eye fields will kind of help coordinate 00:12:27.090 --> 00:12:32.409 some motor movements because this is a part of 00:12:32.409 --> 00:12:38.909 the sensory motor region, which is here. Okay. 00:12:39.169 --> 00:12:41.889 And then on this backside, it's kind of angled. 00:12:43.090 --> 00:12:48.039 It's angled. It's a somatosensory. S1 cortex 00:12:48.039 --> 00:12:52.019 and then the superior colliculus will also because 00:12:52.019 --> 00:12:58.379 this is the occipital lobe here V1 through V4 00:12:58.379 --> 00:13:04.740 will happen maybe even V5 so Remember, we're 00:13:04.740 --> 00:13:07.159 just talking about the superior colliculus. Superior 00:13:07.159 --> 00:13:09.720 colliculus will speak back and forth to visual 00:13:09.720 --> 00:13:12.899 cortex one as well. It's kind of giving it updates. 00:13:13.379 --> 00:13:17.019 And this is happening fast as well. Okay, so 00:13:17.019 --> 00:13:20.179 let's see here. Something that I haven't mentioned 00:13:20.179 --> 00:13:24.600 so far is, I have mentioned it in previous episodes 00:13:24.600 --> 00:13:33.860 though, is the waves. A lot of alpha. Beta gamma 00:13:33.860 --> 00:13:39.519 Low and high gamma. So this is 30 to 80 Hertz 00:13:39.519 --> 00:13:47.440 80 plus 12 to 30 Hertz 8 to 12 a lot of this 00:13:47.440 --> 00:13:52.159 happening in these earliest centuries is Here 00:13:52.159 --> 00:13:57.919 for autism autism versus here for typical With 00:13:57.919 --> 00:14:02.519 a little spike into low gamma to help kind of 00:14:02.519 --> 00:14:07.840 modulate and task switch orient the vision but 00:14:07.840 --> 00:14:13.899 autistics live here okay so this connection here 00:14:13.899 --> 00:14:18.539 is twice as fast nearly twice as fast so from 00:14:18.539 --> 00:14:21.600 retina, superior colliculus, pulmonary, radial 00:14:21.600 --> 00:14:25.159 dorsal to frontal eye fields this is happening 00:14:25.159 --> 00:14:34.779 at around let's see anywhere from 55 to 80 milliseconds. 00:14:34.840 --> 00:14:39.539 Show up kind of sloppy compared to around 80 00:14:39.539 --> 00:14:44.000 to 100 milliseconds for the autistic phenotype 00:14:44.000 --> 00:14:47.639 or for atypicals. It doesn't seem like much but 00:14:47.639 --> 00:14:50.000 that is a lot. But then the frontal eye fields 00:14:50.000 --> 00:14:54.179 will speak back down to the thalamus and also 00:14:54.179 --> 00:14:58.039 the superior colliculus and this connection back 00:14:58.039 --> 00:15:05.899 down is slow and this hurts the eye gaze and 00:15:05.899 --> 00:15:09.320 eye contact and so forth and modulating eye attention 00:15:09.320 --> 00:15:12.820 okay the superior colliculus will also talk to 00:15:12.820 --> 00:15:16.889 the basal ganglia the basal ganglia are Five, 00:15:17.070 --> 00:15:19.570 if we would look at these from the back side 00:15:19.570 --> 00:15:22.190 because it's just going to be easier to see. 00:15:22.470 --> 00:15:25.350 So we have the thalamus and then we have the 00:15:25.350 --> 00:15:28.629 caudate nucleus up through here. The caudate 00:15:28.629 --> 00:15:32.830 nucleus is attached to the putamen. We can just 00:15:32.830 --> 00:15:36.389 say this and the globus pallidus external and 00:15:36.389 --> 00:15:39.490 internal. Globus pallidus external and internal 00:15:39.490 --> 00:15:44.909 make kind of a, it's hard to see, makes a triangle. 00:15:45.960 --> 00:15:50.159 And then below the thalamus is a subthalamic 00:15:50.159 --> 00:15:53.820 nucleus, okay? And the superior colliculus will 00:15:53.820 --> 00:15:57.279 be, let's say, here. And then the substantia 00:15:57.279 --> 00:16:01.940 nigra here, pars reticulata for the GABA and 00:16:01.940 --> 00:16:06.379 pars compacta for the dopamine. The superior 00:16:06.379 --> 00:16:11.860 colliculus will speak to the substantia nigra 00:16:11.860 --> 00:16:15.200 reticulata and the globus pallidus internal. 00:16:16.110 --> 00:16:20.210 Here. It's modulating motor movements. So the 00:16:20.210 --> 00:16:22.789 inputs coming out of the superior colliculus 00:16:22.789 --> 00:16:25.669 are happening faster. The information coming 00:16:25.669 --> 00:16:29.509 back down to the superior colliculus is delayed. 00:16:31.289 --> 00:16:37.730 So afferents are heightened. Fast. Efferents 00:16:37.730 --> 00:16:41.789 are delayed. with the superior colliculus. And 00:16:41.789 --> 00:16:44.750 this is hurting vision. It's hurting eye movements, 00:16:45.149 --> 00:16:48.850 saccades. They're called saccades. The eye movements 00:16:48.850 --> 00:16:54.509 are called saccades. And this is hurting. So 00:16:54.509 --> 00:16:58.250 we just draw out the brain here. You know, this 00:16:58.250 --> 00:17:01.629 is the prefrontal cortex here. And then it goes 00:17:01.629 --> 00:17:06.700 up the parietal lobe. Parietal lobe. is here, 00:17:06.859 --> 00:17:09.539 and the superior colliculus will also speak up 00:17:09.539 --> 00:17:15.400 to here, but mostly the somatosensory cortex 00:17:15.400 --> 00:17:19.880 here. And then this is the occipital in the back. 00:17:20.400 --> 00:17:24.700 So V1 to V5. But I only want to talk about superior 00:17:24.700 --> 00:17:30.079 colliculus, not the rest of the eye inputs, not 00:17:30.079 --> 00:17:33.359 the rest of the eyes. just because we can hit 00:17:33.359 --> 00:17:37.319 this mesencephalon. But the big thing here is 00:17:37.319 --> 00:17:41.500 heightened activity out of the superior colliculus 00:17:41.500 --> 00:17:45.299 and delayed inputs coming back down. This is 00:17:45.299 --> 00:17:50.500 a feed forward feedback type of movements here 00:17:50.500 --> 00:17:54.339 so that we can have attention to the outside 00:17:54.339 --> 00:17:58.019 world. Remember the mesencephalon has three main 00:17:58.019 --> 00:18:03.500 goals here. Sensory integration, right? This 00:18:03.500 --> 00:18:06.819 is easy now. A bunch of sensory is happening 00:18:06.819 --> 00:18:10.359 throughout this mesencephalon. A lot of sensory 00:18:10.359 --> 00:18:15.559 connections. Touch, hearing, auditory, vision 00:18:15.559 --> 00:18:21.420 coming this way, and then speaking to the thalamus. 00:18:21.700 --> 00:18:24.299 There's a close connection here with the thalamus. 00:18:24.359 --> 00:18:28.720 So it's like a feedback loop. And also the cerebellum. 00:18:28.779 --> 00:18:34.779 cerebellums here with the um purgenji cells lots 00:18:34.779 --> 00:18:39.000 of purgenji cells here which are all inhibitory 00:18:39.000 --> 00:18:43.579 and it's kind of shutting off unwanted movements 00:18:43.579 --> 00:18:48.079 noise if you will the second row is the motor 00:18:48.079 --> 00:18:52.099 movements and that's going to be in large part 00:18:52.099 --> 00:18:55.819 not necessarily the eyes but with this basal 00:18:55.819 --> 00:18:59.230 ganglia this is the basal ganglia from the backside 00:18:59.230 --> 00:19:02.730 and then orienting attention to the outside world. 00:19:02.890 --> 00:19:06.930 It's the mesencephalon. Fast acting in and out 00:19:06.930 --> 00:19:10.829 to orient the attention and then slow acting 00:19:10.829 --> 00:19:16.549 back to back to the mesencephalon for eye movements. 00:19:17.549 --> 00:19:20.930 So there are a lot of delays happening. This 00:19:20.930 --> 00:19:23.369 is the superior colliculus. It's a relay station 00:19:23.369 --> 00:19:28.400 for vision and it's very fast acting stuff. especially 00:19:28.400 --> 00:19:30.900 with the autistic phenotype because there's a 00:19:30.900 --> 00:19:34.599 lot of gamma waves compared to alpha and beta 00:19:34.599 --> 00:19:38.240 and sometimes they're even coupled there's this 00:19:38.240 --> 00:19:42.180 thing called theta gamma coupling or alpha theta 00:19:42.180 --> 00:19:45.539 coupling this is four to eight this is helping 00:19:45.539 --> 00:19:49.779 smooth task switching is what theta is doing 00:19:49.779 --> 00:19:54.390 with this background theta So gamma is what's 00:19:54.390 --> 00:19:57.230 activated, the circuitry, the neural correlates 00:19:57.230 --> 00:20:01.190 activating, and then theta is kind of scanning 00:20:01.190 --> 00:20:05.109 all this background noise to help modulate it. 00:20:05.210 --> 00:20:08.509 So the superior colloculus is one of the fascinating 00:20:08.509 --> 00:20:12.470 brain region. Remember in the barn owls, it's 00:20:12.470 --> 00:20:15.609 called optic tectum because the mesencephalon 00:20:15.609 --> 00:20:19.849 can be broken down into three areas. Tectum and 00:20:19.849 --> 00:20:24.940 tecmitum or two of the three. The third one is 00:20:24.940 --> 00:20:29.160 Cerebral Prudential. I don't know what that is, 00:20:29.339 --> 00:20:33.400 to be honest, but the mesencephalon is very fast 00:20:33.400 --> 00:20:37.160 acting relay station. It's very small and I think 00:20:37.160 --> 00:20:39.579 that's why it doesn't subdivide because these 00:20:39.579 --> 00:20:43.740 three crucial, these are three crucial rows of 00:20:43.740 --> 00:20:48.279 the mesencephalon. So evolution says no more. 00:20:48.619 --> 00:20:53.019 It has to be on point. has to be fully developed 00:20:53.019 --> 00:20:56.480 because it needs to be because the living organism 00:20:56.480 --> 00:20:59.019 remember the role of the central nervous system 00:20:59.019 --> 00:21:03.480 is to move the living organism and in large part 00:21:03.480 --> 00:21:08.140 these three things is it this is it for the living 00:21:08.140 --> 00:21:11.859 organism the the biggest roles here don't you 00:21:11.859 --> 00:21:14.240 think it's fascinating that the mesencephalon 00:21:14.240 --> 00:21:17.900 which is just right here it's called the midbrain 00:21:17.930 --> 00:21:21.069 This is called the midbrain, but if the bottom 00:21:21.069 --> 00:21:23.950 of the brainstem is here and the top of the cortex 00:21:23.950 --> 00:21:27.910 is here, in no way is that in the middle. All 00:21:27.910 --> 00:21:31.130 of this stuff that came later is just kind of 00:21:31.130 --> 00:21:36.890 helping and hurting the human because there's 00:21:36.890 --> 00:21:40.049 too much here. This is too powerful. Mesencephalon 00:21:40.049 --> 00:21:42.009 superior colliculus eye movements.