WEBVTT 00:00:03.517 --> 00:00:10.517 This is the Convergent Science Network podcast. Leading researchers in the domain 00:00:10.517 --> 00:00:16.737 of neuroscience, brain theory and technology are interviewed by Paul Verschure and Tony Prescott. 00:00:19.577 --> 00:00:23.937 This is Paul Verschure and Tony Prescott with the Convergent Science Network 00:00:23.937 --> 00:00:29.297 podcast. In this episode that we record as part of the Converter Science Network 00:00:29.297 --> 00:00:32.817 Barcelona Cognition Brain Technology Summer School, we're talking with Nick Strausfeld. 00:00:33.497 --> 00:00:39.557 So Nick, you started your talk with this notion of placing the study of biology 00:00:39.557 --> 00:00:42.557 always in the context of evolution because it wouldn't make any sense. 00:00:42.757 --> 00:00:43.737 So where's that coming from? 00:00:43.997 --> 00:00:48.157 Well, it's coming from Theodosius Dabiansky's statement, which he made in the 00:00:48.157 --> 00:00:56.577 in the 50s, and I think was very relevant to what was happening in biology then, 00:00:56.657 --> 00:01:00.537 which was a lot of comparative work being done in all sorts of different fields. 00:01:00.817 --> 00:01:04.977 And it's worthwhile reminding people today of this, because we've become so 00:01:04.977 --> 00:01:07.977 incredibly specialized and canonized in our research. 00:01:08.637 --> 00:01:13.737 So there are these horrible things called model organisms, which I loathe the term model. 00:01:13.857 --> 00:01:16.637 These are animals. animals, but there is about three animals that have been 00:01:16.637 --> 00:01:18.077 funded, at least in America. 00:01:19.197 --> 00:01:22.817 You can't really tell anything about evolution from the three. 00:01:22.977 --> 00:01:26.877 Evolution will tell us about very, very interesting aspects of design. 00:01:27.597 --> 00:01:32.317 I don't mean that in the bad sense. 00:01:32.517 --> 00:01:40.657 I mean the results of evolutionary innovations and what was the beginning. 00:01:40.797 --> 00:01:45.517 In the nervous system, So, for example, what were the basic circuits that provided 00:01:45.517 --> 00:01:47.017 an organism with choice, 00:01:47.337 --> 00:01:56.857 with allocentric memory, with the ability to integrate odorant signals to provide behavior, 00:01:57.077 --> 00:02:02.117 and basically all the kind of senses it has, and what kind of nervous system 00:02:02.117 --> 00:02:05.317 allowed the integration of those senses to provide elaborate behaviors? 00:02:06.457 --> 00:02:11.197 And one is only going to get to those answers if one actually does comparative work. 00:02:11.737 --> 00:02:15.137 And thinks about how these things have evolved over time. But then, 00:02:15.237 --> 00:02:17.917 so where do you stand on that right now? 00:02:18.177 --> 00:02:22.437 So you're one of the world's experts on definitely the insect brain. 00:02:23.737 --> 00:02:28.397 So how should we think about the insect brain? What are then these basic design features it has? 00:02:28.497 --> 00:02:31.797 What are the basic functional capabilities that are supported with it? 00:02:31.877 --> 00:02:32.737 How should we think about that? 00:02:32.957 --> 00:02:35.597 Well, we have to start thinking about where do insects come from? 00:02:36.197 --> 00:02:40.597 And the evidence is very strong. and they have originated from marine ancestors, 00:02:40.757 --> 00:02:42.437 which we call the crustaceans. 00:02:43.037 --> 00:02:46.177 And then one has to ask, what does come between insects and crustaceans? 00:02:46.657 --> 00:02:48.837 What do their common ancestors perhaps look like? 00:02:49.695 --> 00:02:53.915 And if one can then, you know, resolve the commonalities of the two, 00:02:54.075 --> 00:02:59.835 then one has an idea of the ancestral brain, the common birth of insects and crustaceans. 00:02:59.855 --> 00:03:04.055 Then one has to go even deeper in time and ask, well, what about the ancestors of that ancestor? 00:03:06.275 --> 00:03:11.475 When did the first insect-like brain or the crustacean-like brain evolve in 00:03:11.475 --> 00:03:14.215 geological time? And that's much more difficult, of course. 00:03:14.455 --> 00:03:18.195 Right. But now, what are the core structures in that brain that you think we 00:03:18.195 --> 00:03:20.355 should be focusing on in that? in that exploration? 00:03:20.595 --> 00:03:24.235 Well, you can ask questions about the core structures, say, of a particular 00:03:24.235 --> 00:03:28.575 modality or sensory organ, such as the compound eye. 00:03:29.455 --> 00:03:32.875 So what are the core structures of the compound eye, the core circuits that 00:03:32.875 --> 00:03:37.415 allow motion detection, for example, motion vision, figure ground discrimination? 00:03:38.675 --> 00:03:40.475 You can actually resolve some 00:03:40.475 --> 00:03:46.095 of the neurons that are involved in those computations in a fly's eye. 00:03:47.035 --> 00:03:49.995 And then you need to get to the actual circuits that 00:03:49.995 --> 00:03:53.175 provide those computations and not just neurons that 00:03:53.175 --> 00:03:56.035 encode those computations and that's again 00:03:56.035 --> 00:03:59.115 more difficult so the search image could develop. 00:03:59.115 --> 00:04:02.955 From looking at much simpler systems what. 00:04:02.955 --> 00:04:06.215 Do they have in common with the fly system for example and so 00:04:06.215 --> 00:04:09.035 if you compare across many many different attacks or say 00:04:09.035 --> 00:04:12.055 of flies flies that have you know have 00:04:12.055 --> 00:04:14.955 they have ballistic flight of flies that can hover flies that 00:04:14.955 --> 00:04:17.815 do this that do that and then you ask what do they have in common 00:04:17.815 --> 00:04:20.495 all these visual systems what are the 00:04:20.495 --> 00:04:23.455 common denominators if you like and if you find those then 00:04:23.455 --> 00:04:26.315 you can ask questions about are those the really the 00:04:26.315 --> 00:04:29.355 principal elements that provide information about motion. 00:04:29.355 --> 00:04:32.495 Detection and then go to the crustaceans do those existing 00:04:32.495 --> 00:04:35.235 crustaceans and then go even to more 00:04:35.235 --> 00:04:38.295 simple organisms such as centipedes right so but then 00:04:38.295 --> 00:04:41.535 if you talk about search image you really mean a 00:04:41.535 --> 00:04:44.175 structural template it's an anatomical template or is 00:04:44.175 --> 00:04:49.415 more than that um the search 00:04:49.415 --> 00:04:53.395 image develops from from really understanding at 00:04:53.395 --> 00:04:56.255 least one circuit in one organism and you ask 00:04:56.255 --> 00:04:59.215 then is that circuit or are those neurons visible are 00:04:59.215 --> 00:05:03.115 they are they obtainable in other other species that's 00:05:03.115 --> 00:05:06.055 the search image yeah but now 00:05:06.055 --> 00:05:08.775 where do you see the the origins of that of that 00:05:08.775 --> 00:05:11.375 nervous system because in some sense you could also are you look at all 00:05:11.375 --> 00:05:14.875 started with let's say chemical sensing and the rest evolves from 00:05:14.875 --> 00:05:18.075 there from then absolutely right so yes yes 00:05:18.075 --> 00:05:22.735 i mean i i would i would envisage that the the chemical sensors are the earliest 00:05:22.735 --> 00:05:30.075 um before there was um highly developed vision um but the actual computational 00:05:30.075 --> 00:05:36.075 circuits that provides provided choice behavioral choice or for example memory of place. 00:05:36.375 --> 00:05:43.175 They can operate equally well in a chemical environment as in a visual environment 00:05:43.175 --> 00:05:44.075 or even a tactile environment. 00:05:45.780 --> 00:05:53.820 So the basic organization of the brain was, one could say, it was independent of the modality. 00:05:53.880 --> 00:05:58.040 Because it wasn't, because certainly it had to evolve in conjunction with the present modality. 00:05:58.340 --> 00:06:03.380 Right. But it can employ other modalities. In fact, we have a very good example 00:06:03.380 --> 00:06:07.560 in one species of insect, where the mushroom bodies, which are in Drosophila 00:06:07.560 --> 00:06:12.460 and many other insects, they get one of their major inputs from the olfactory system. 00:06:13.080 --> 00:06:17.480 In a species of insect called whirligig beetles, they completely switch modalities 00:06:17.480 --> 00:06:19.740 and get all their inputs from the visual system. 00:06:21.520 --> 00:06:26.900 If these are place memory centers, which we think they are, then in one instance 00:06:26.900 --> 00:06:29.240 they are using olfaction, and in the other they're using vision. 00:06:29.420 --> 00:06:33.260 You just get the switch. But then that would imply that you're thinking of some 00:06:33.260 --> 00:06:37.200 sort of backbone structure, a particular backbone structure that you can sort 00:06:37.200 --> 00:06:41.640 of mold to, let's say, the sensory ecology, the behavioral ecology of the organism. 00:06:41.880 --> 00:06:44.920 So what is that backbone structure? So I'll give you an example. 00:06:45.320 --> 00:06:50.760 The olfactory system of insects and also of crustaceans, the first synaptic 00:06:50.760 --> 00:06:53.480 neuropil is a system of glomeruli. 00:06:53.880 --> 00:06:58.680 And in insects, each glomerulus receives the inputs from a set of olfactory 00:06:58.680 --> 00:07:04.100 receptors that encode the same kinds of ligands. 00:07:06.160 --> 00:07:11.660 So one type of olfactory sensory receptor neuron will send its axon to one particular kind of glomerulus. 00:07:12.240 --> 00:07:17.220 So when you have 40 different kinds of receptors, you have 40 glomeruli each 00:07:17.220 --> 00:07:19.740 getting inputs from that particular type of receptor, right? 00:07:19.820 --> 00:07:23.540 So when you go to the visual system, you see the remarkable thing that in the 00:07:23.540 --> 00:07:27.440 next ganglia up, which is the proto cerebrum of the insect, you have a glomerular 00:07:27.440 --> 00:07:32.200 organization into which are segregating pathways in the visual system. 00:07:32.620 --> 00:07:38.840 And this suggests that you have this template of computational entities which 00:07:38.840 --> 00:07:40.120 are repeated segment for segment, 00:07:40.400 --> 00:07:44.820 which can deal with the visual input or with the olfactory input or with the 00:07:44.820 --> 00:07:48.860 tactile input, but the actual computational network can deal with. 00:07:49.570 --> 00:07:54.450 Is in principle the same for any sensory modality, which is remarkable. 00:07:54.690 --> 00:07:57.110 And this is quite, you know, worrying in a sense. 00:07:57.410 --> 00:08:02.330 Right. So, but in this example, you would say, I guess a lobular would have a glomerular. 00:08:02.590 --> 00:08:07.130 No, no, no, no, no, definitely not. Okay. The lobular is composed of many, 00:08:07.210 --> 00:08:11.850 many palisades of neurons, types of neurons, and each palisade encodes a visual 00:08:11.850 --> 00:08:17.090 primitive, such as an an oriented edge of one kind or the other. 00:08:17.270 --> 00:08:21.310 And each of these palisades then sends its axons convergently to a glomerulus. 00:08:21.510 --> 00:08:26.470 So each glomerulus represents a particular visual modality, an edge or a color or whatever. 00:08:26.790 --> 00:08:32.010 Then interactions amongst these glomeruli further reconstruct the visual image 00:08:32.010 --> 00:08:35.730 and further provide higher order primitives. The same is happening in the olfactory system. 00:08:36.670 --> 00:08:41.650 So each glomerulus receives information about a small sort of palette of ligands. 00:08:41.650 --> 00:08:46.510 And interactions amongst these various glomeruli provide information about the odor, 00:08:46.690 --> 00:08:51.370 not the odorant but the odor, the combinations so it's the same principle actually 00:08:51.370 --> 00:08:52.750 I understood the principle, 00:08:52.930 --> 00:08:56.490 I'm just trying to place it in this visual hierarchy because in the chemical 00:08:56.490 --> 00:09:01.330 sensing system it's just one step away from the receptor that's the question 00:09:01.330 --> 00:09:02.270 that is always addressed. 00:09:03.650 --> 00:09:08.570 The homologue, if you like, the functional homologue of the antenna in the visual 00:09:08.570 --> 00:09:12.570 system is the entire retentovic mosaic down to the output of the lobular. 00:09:12.950 --> 00:09:16.330 Oh, you mean the antenna in the chemical sensing system? Yes. 00:09:16.490 --> 00:09:19.890 The antenna in the chemical sensors, the equivalent of that in the visual system 00:09:19.890 --> 00:09:21.290 is the lamina medulla in the lobular. 00:09:21.710 --> 00:09:24.990 And the outputs in the lobular are equivalent to the outputs in the antenna. 00:09:25.290 --> 00:09:30.210 All right. Okay. So then where would I find the glomerular structures of the 00:09:30.210 --> 00:09:31.750 optic system it detects? 00:09:32.010 --> 00:09:36.150 Beneath the lobular. Okay. Very good. And you will find also an equivalent to 00:09:36.150 --> 00:09:39.250 something like a projection neuron type readout of this? Yes. 00:09:39.250 --> 00:09:40.710 These would be your whitefield neurons? 00:09:40.950 --> 00:09:43.870 Yes. That's what we're looking at right now. Okay. Very good. That's beautiful. 00:09:44.410 --> 00:09:48.070 But then in some sense, we're still talking about the sensory front end of this, right? 00:09:48.130 --> 00:09:52.910 So the core structure, this archetypical backbone structure should also be relying 00:09:52.910 --> 00:09:56.010 on structures that are mapping now sensor states into action. 00:09:56.290 --> 00:10:00.250 You're quite right. So you have these reiterated ganglia down the rest of the body. 00:10:01.030 --> 00:10:04.750 And in each ganglia, you have domains, glomerular-like domains. 00:10:04.970 --> 00:10:09.170 And each domain is receiving one or another kind of sensory input. often mapped. 00:10:09.350 --> 00:10:15.550 If it's an input of the mechanosensory system, then that particular type of 00:10:15.550 --> 00:10:19.010 receptor will invade one of these domains, and you'll have a map representation 00:10:19.010 --> 00:10:20.650 of those terminals in the domain. 00:10:21.550 --> 00:10:25.070 And then you have local interneurons linking these various domains and integrating 00:10:25.070 --> 00:10:29.070 all this sensory information just as it does in the olfactory system or the visual system. 00:10:29.370 --> 00:10:35.090 But what happened to these really central structures like mushroom bodies or protoceberum? 00:10:35.150 --> 00:10:39.310 I mean, they're sort of in between that mapping, right? And they're unique to 00:10:39.310 --> 00:10:41.850 the first segment of the brain. 00:10:42.590 --> 00:10:44.790 And where they come from is a real puzzle. 00:10:45.996 --> 00:10:51.296 And my suspicion is that they are actually derived from the ancestor of the 00:10:51.296 --> 00:10:53.256 Lophotrachazones and Ectisazones. 00:10:53.356 --> 00:10:57.476 And you see mushroom bodies and central body complexes in worms, 00:10:57.696 --> 00:11:05.976 in polychaete worms, in what's called the acron, which is an A-segmental neuropil. 00:11:06.076 --> 00:11:07.556 It does not belong to a segment. 00:11:08.036 --> 00:11:13.236 And so the idea is, and there are many opponents to this idea, idea. 00:11:13.276 --> 00:11:18.856 The idea is that the modern arthropod brain is actually composed of four components. 00:11:20.136 --> 00:11:23.296 Three of them derive from ganglia, primitively from ganglia, 00:11:23.476 --> 00:11:28.456 and the fourth component right at the front is the leftover from the common ancestor. 00:11:29.036 --> 00:11:32.716 And you still find this in polychaete worms separated from the rest of the system. 00:11:32.916 --> 00:11:36.956 And that's been integrated into the first segment of the insect or crustacean brain. 00:11:37.156 --> 00:11:41.756 And it is the substrate for the central body complex and the mushroom bodies. Right. 00:11:41.896 --> 00:11:46.796 And that then provides you, let's say, the integrative infrastructure for these 00:11:46.796 --> 00:11:48.316 different sensory modalities. 00:11:48.316 --> 00:11:53.556 It provides the substrates for high-level computations of, say, of allocentricity. 00:11:55.436 --> 00:12:01.456 A relative memory amongst individuals, and also behavioral choice, 00:12:01.616 --> 00:12:07.656 and complex things like dexterity and such like. 00:12:08.276 --> 00:12:11.276 These are the, this is the brain within the brain, if you like. 00:12:11.496 --> 00:12:15.956 Right. Okay. The integration amongst sensory systems can be quite local. 00:12:16.964 --> 00:12:20.264 To provide reflex actions. But the integration of accentuators and to provide 00:12:20.264 --> 00:12:22.784 these more complex behaviors requires these higher centers. 00:12:23.364 --> 00:12:28.444 Right. So now we have a bit of an idea what sort of the key components of such 00:12:28.444 --> 00:12:30.024 an archetypical brain could look like. 00:12:30.404 --> 00:12:36.384 But you also emphasize that, let's say, the specifics of the ecology of the 00:12:36.384 --> 00:12:38.984 animal might lead to variations now in that design. 00:12:39.564 --> 00:12:42.704 Yeah. So how does that really happen? Is it only through, let's say, 00:12:42.744 --> 00:12:45.824 evolutionary pressures or over long timescales? 00:12:45.824 --> 00:12:49.064 Or are there more rapid ways to let's say reconfigure and 00:12:49.064 --> 00:12:52.544 configure these these prototype brains 00:12:52.544 --> 00:12:55.544 you don't know how plastic they are um right in 00:12:55.544 --> 00:12:59.164 terms of the lifetime of a single organism but with regard 00:12:59.164 --> 00:13:02.264 to the structures and the number of neurons and the connectivities 00:13:02.264 --> 00:13:09.064 um the differences between taxa are clearly the result of of of many millions 00:13:09.064 --> 00:13:14.604 of years of evolution diversions but still you will you'll find also of slight 00:13:14.604 --> 00:13:21.884 deviations within specific taxa or species dependent on the ecologies they're in. 00:13:22.144 --> 00:13:24.404 The difference is that's the stuff of evolution. 00:13:24.704 --> 00:13:28.044 I mean, you look at the olfactory lobes across lots of Drosophila and you find 00:13:28.044 --> 00:13:31.344 all these sort of variations of wiring, but you've got to have this. 00:13:31.504 --> 00:13:37.784 Otherwise, you will not have selectivity. You will not have the species responding 00:13:37.784 --> 00:13:38.744 to selective pressures. 00:13:39.244 --> 00:13:45.704 Some of those variations are fitter, greater fitness than others on the organism. 00:13:45.944 --> 00:13:47.444 Yeah, you must have variation. 00:13:47.744 --> 00:13:53.264 How do you see that exploratory mechanism? Because, I mean, within every species, 00:13:53.404 --> 00:13:58.444 in this backbone neural structure that gives it the nervous system, 00:13:58.644 --> 00:14:02.304 there are exploratory mechanisms that now are imposing variability on this. 00:14:02.404 --> 00:14:06.644 And, for instance, in your talk you mentioned that possibly a computational 00:14:06.644 --> 00:14:08.864 substrate for this kind of variability in, 00:14:08.904 --> 00:14:12.104 let's say, visual processing could be the lobular plate because there you 00:14:12.104 --> 00:14:15.564 can start to play with how you integrate this kind of information so would 00:14:15.564 --> 00:14:18.264 you then predict that also it's leveled lobular plate you would find the highest 00:14:18.264 --> 00:14:24.544 variability to allow a species to explore let's say the variability of its visual 00:14:24.544 --> 00:14:28.324 space in which it has to behave yeah that's true and in fact when we look across 00:14:28.324 --> 00:14:32.364 different species of flies for example which and which have actually very different 00:14:32.364 --> 00:14:34.904 visual visually induced flying behaviors. 00:14:36.076 --> 00:14:39.976 We do find very, very fascinating differences of the organization of the lobular 00:14:39.976 --> 00:14:41.676 plate and the lobular, but not the medulla and lamina. 00:14:42.296 --> 00:14:45.456 Right, okay. What about the role of development here? 00:14:45.616 --> 00:14:52.136 Because I've heard, for instance, in the locust, a significant effect on the 00:14:52.136 --> 00:14:56.836 development of the brain, for instance, due to whether or not the animal is 00:14:56.836 --> 00:14:58.116 going to be part of a swarm, 00:14:58.596 --> 00:15:02.116 because there's a high density of population or is going to be perhaps more 00:15:02.116 --> 00:15:05.536 of a low-density individual locust. 00:15:05.536 --> 00:15:09.876 And being part of a swarm somehow makes the locus develop a larger brain. 00:15:10.116 --> 00:15:11.736 Yeah, that's a very interesting point. 00:15:13.476 --> 00:15:17.196 Actually, it's fascinating. What's happening in the locus? Are the neurons actually 00:15:17.196 --> 00:15:18.356 sprouting more dendrites? 00:15:18.976 --> 00:15:23.476 Certainly a radical difference of size of the brain overall. 00:15:24.036 --> 00:15:28.396 Does that pertain to all the centers? Does that pertain to certain neuropills? 00:15:29.296 --> 00:15:33.136 I would put my money on the central body complex and its associated structures 00:15:33.456 --> 00:15:36.656 and because that's the decision making part of the brain but 00:15:36.656 --> 00:15:39.596 i don't think it's been followed through yet and and and 00:15:39.596 --> 00:15:42.516 and i look forward to seeing papers that are following 00:15:42.516 --> 00:15:45.276 through on this but it's a you know 00:15:45.276 --> 00:15:48.396 it's it's very very very interesting but 00:15:48.396 --> 00:15:51.656 it does suggest that the real uh potential for 00:15:51.656 --> 00:15:54.956 the environment to affect the developmental process 00:15:54.956 --> 00:15:58.616 so that some of these differences we get uh are partly 00:15:58.616 --> 00:16:01.776 due to maybe some genetic change but also when the 00:16:01.776 --> 00:16:04.496 the environment changes that there's plasticity in the 00:16:04.496 --> 00:16:08.116 development of the system which can really result in some important changes 00:16:08.116 --> 00:16:10.936 one puzzle i think is that these changes happen 00:16:10.936 --> 00:16:14.456 before the locus mix becomes either a goes 00:16:14.456 --> 00:16:20.056 into you know into it into the swarming mode or or the or the actual wandering 00:16:20.056 --> 00:16:28.136 um continues the wandering mode that it had as as as a juvenile um so it's as 00:16:28.136 --> 00:16:34.356 if If the brain is preparing itself for the next role, 00:16:34.616 --> 00:16:40.156 which is really amazing, and it must be under some kind of hormonal control and so forth. 00:16:41.516 --> 00:16:45.796 Again, I think we know too little about what is actually changing to put one's 00:16:45.796 --> 00:16:47.796 finger on why it's changing. 00:16:48.196 --> 00:16:51.956 It is a pity. I'd like to know that. so what 00:16:51.956 --> 00:16:56.096 struck me about your talk is that one of the things that really fascinates you 00:16:56.096 --> 00:17:02.976 is to trace back modern brains or modern nervous systems to what the ancestral 00:17:02.976 --> 00:17:07.476 brains might have looked like and of course that's a task where you have to 00:17:07.476 --> 00:17:08.476 look at indirect evidence, 00:17:09.556 --> 00:17:14.656 because there are lots of clues but nothing definitive really that can tell 00:17:14.656 --> 00:17:17.036 us what was the path that evolution followed. 00:17:17.316 --> 00:17:22.116 So, can you just summarize quickly the range of clues that you think are important 00:17:22.116 --> 00:17:24.796 to reconstructing evolutionary history here? 00:17:26.676 --> 00:17:30.716 Yeah, well, the clues must be constrained to, 00:17:32.548 --> 00:17:35.428 to what one would imagine would be visible in a fossil. 00:17:35.928 --> 00:17:39.568 So, isolated neuro pills, one from the other, that are connected by tracts, 00:17:39.648 --> 00:17:43.808 for example, one would be able to see these clearly in a fossil if they existed. 00:17:44.868 --> 00:17:48.088 Internal structures of the brain would be very unlikely to see them, although, 00:17:48.628 --> 00:17:53.668 the brain I talked about today, which is 535 million years old in a stem group 00:17:53.668 --> 00:18:00.048 arthropod, we can actually see differences of texture within the outline of the brain. 00:18:00.328 --> 00:18:03.948 That suggests, for example, the olfactory lobes. And it would be nice to see 00:18:03.948 --> 00:18:08.828 then other striations or pronounced, you know, maybe outlines, 00:18:09.068 --> 00:18:11.028 internal outlines that would suggest, 00:18:11.928 --> 00:18:19.608 the presence of certain centers that we know are required for certain functions of the baby modern taxa. 00:18:22.068 --> 00:18:28.848 Another thing we would look for is the kind of fusion of segments that comprise the brain. 00:18:31.128 --> 00:18:35.828 In modern crustaceans, melacotra, crustaceans, and insects, there are three 00:18:35.828 --> 00:18:38.008 segments that are fused to comprise the brain. 00:18:38.088 --> 00:18:43.368 And in some species, even the subosophageal ganglia, the three subosophageal 00:18:43.368 --> 00:18:47.048 ganglia, have moved up and have become almost fused with the superosophageal 00:18:47.048 --> 00:18:49.868 ganglia so that the gut just penetrates the brain. 00:18:50.048 --> 00:18:53.068 There's no clear divisions of ganglia. 00:18:53.208 --> 00:18:58.548 The whole thing becomes highly condensed, which is a mark of modernity, 00:18:58.548 --> 00:19:00.028 perhaps evolutionary modernity. 00:19:00.028 --> 00:19:02.728 Now we're late to go and look at these ancient brains and 00:19:02.728 --> 00:19:06.028 ask is that true um how much condensation of 00:19:06.028 --> 00:19:10.168 the nervous system can one see in in the head and and for the one that the animal 00:19:10.168 --> 00:19:15.168 i was showing you today it's surprising that the first three segment of firstly 00:19:15.168 --> 00:19:20.068 brain fragments are fused we were really surprised to see this quite shocked 00:19:20.068 --> 00:19:23.748 actually um but that's shows us it's already quite advanced. 00:19:24.508 --> 00:19:27.808 So you're talking about the sort of anatomical morphological markers. 00:19:28.288 --> 00:19:34.128 Nowadays there are a lot of molecular tools looking at DNA, RNA and so on that 00:19:34.128 --> 00:19:37.608 can tell us a lot about the relationships between different animal groups. 00:19:38.028 --> 00:19:43.388 But I think you were persuading me in your talk this morning that this isn't 00:19:43.388 --> 00:19:48.968 enough although we might get some idea about what's related to what But if we 00:19:48.968 --> 00:19:50.548 really want to understand the history, 00:19:50.748 --> 00:19:54.008 we do need the anatomy. Yes. 00:19:54.788 --> 00:20:00.608 A case in point is the origin of insects. Did they derive from a brachiopod-like 00:20:00.608 --> 00:20:04.608 ancestor or a remipede-like ancestor or a malacostrican-like ancestor? 00:20:05.628 --> 00:20:09.688 The molecular studies suggest malacostric and remipede. 00:20:09.808 --> 00:20:14.228 But there are other molecular studies which would equally well suggest brachiopod. 00:20:15.444 --> 00:20:19.724 One wouldn't know unless one went to the morphology. And morphology suggests 00:20:19.724 --> 00:20:23.484 brachiopods are very simple, therefore they must be maybe more primitive than 00:20:23.484 --> 00:20:24.704 insects, which are more complex. 00:20:25.244 --> 00:20:28.924 Which then suggests that insect brains and malacostricum brains have evolved 00:20:28.924 --> 00:20:30.924 by convergence, which is probably nonsense. 00:20:31.284 --> 00:20:39.984 So one needs these various strategies for using cladistics to see whether or 00:20:39.984 --> 00:20:43.184 not there's evidence for reversal and for loss of structures. 00:20:43.184 --> 00:20:46.804 Structures, that gives the false impression of primitivity. 00:20:47.764 --> 00:20:50.964 And one cannot possibly do that just using molecular techniques. 00:20:51.164 --> 00:20:53.684 One has to go in there using anatomical methods. 00:20:54.244 --> 00:20:59.264 So there is this bias that we have to think that things get more complicated over time. 00:20:59.484 --> 00:21:04.484 But in fact, there's evidence that in some cases, things will actually get simpler. 00:21:04.564 --> 00:21:05.704 Like tapeworms, for example. 00:21:06.504 --> 00:21:11.024 Can you give an example of a reversal? of a reversal. Well, parasites. 00:21:11.404 --> 00:21:15.284 I mean, typeworms are leptotrichozoans. They don't even have a brain. 00:21:15.364 --> 00:21:16.804 I mean, they've lost everything, really. 00:21:17.024 --> 00:21:21.644 And they're just reproductive organs living off one's gut. 00:21:21.944 --> 00:21:28.284 I mean, there are lots of nematodes. These are ectozoans. They molt. 00:21:29.324 --> 00:21:32.644 Presumably, their ancestors had somewhat more complicated. 00:21:34.584 --> 00:21:37.944 So, that means there are a lot of examples of reduction and loss. 00:21:37.944 --> 00:21:42.564 But also, as Tony mentioned earlier, this sort of like simple heuristic that 00:21:42.564 --> 00:21:45.484 would say, look, brains go from simple to complex is not working. 00:21:46.224 --> 00:21:50.224 It's not as a guideline. It's not helping us. But what should replace this heuristic? 00:21:50.304 --> 00:21:52.124 What's the heuristic that we shouldn't follow? 00:21:53.844 --> 00:21:56.244 That's a difficult question to answer. Yeah. 00:21:57.998 --> 00:22:01.038 No heuristic i don't know i think stephen 00:22:01.038 --> 00:22:03.938 gould compared evolution to a drunk man 00:22:03.938 --> 00:22:06.798 stumbling along the pavement so sometimes you move 00:22:06.798 --> 00:22:10.118 further out from the wall which could be an increasing complexity sometimes 00:22:10.118 --> 00:22:13.918 you you move closer that's a nice analogy yeah so and 00:22:13.918 --> 00:22:16.658 another interesting thing i think that came from your 00:22:16.658 --> 00:22:19.578 talk which perhaps also links with some of stephen j gould's 00:22:19.578 --> 00:22:22.338 ideas is that we i think 00:22:22.338 --> 00:22:25.458 used to imagine that evolution was a slow process 00:22:25.458 --> 00:22:28.218 and a gradual process over hundreds of 00:22:28.218 --> 00:22:31.078 million years of years we got these advanced forms or 00:22:31.078 --> 00:22:33.998 these recent forms we see today but actually what 00:22:33.998 --> 00:22:37.438 was striking about your talk today was you were arguing that 00:22:37.438 --> 00:22:40.718 some of the things that we see in contemporary organisms were 00:22:40.718 --> 00:22:43.578 already present really shortly after the 00:22:43.578 --> 00:22:48.998 appearance of the first multi-celled animals yes shortly meaning yes well yes 00:22:48.998 --> 00:22:53.538 50 million years is a very short time yes exactly so this is really quite quite 00:22:53.538 --> 00:23:00.058 fascinating you have You have this plethora of different body forms in Camry 00:23:00.058 --> 00:23:01.118 called the Camryn Explosion. 00:23:01.338 --> 00:23:07.998 These different arthropod-like animals suggesting very, very rapid evolution of morphologies. 00:23:08.138 --> 00:23:12.498 And yet, the ground pattern of the nervous system, probably across them all, 00:23:12.618 --> 00:23:16.938 is this very, very consistent organization that exists today. day. 00:23:17.058 --> 00:23:23.378 So you have, in a sense, stasis and slow elaboration of the ground pattern of the nervous system, 00:23:23.518 --> 00:23:28.478 and then this very, very rapid elaboration of appendages and other decorations 00:23:28.478 --> 00:23:32.938 that provide the inputs to this consistent organization of the CNS. 00:23:33.218 --> 00:23:39.698 Would you argue that then still that very basic proto-brain was the facilitator 00:23:39.698 --> 00:23:41.058 of all this variability? No. 00:23:42.253 --> 00:23:46.873 No, no, no. It had to accommodate this variability through evolutionary time. 00:23:47.093 --> 00:23:52.233 I don't think it was the facilitator. Although one can't really imagine how 00:23:52.233 --> 00:23:57.253 an organism could develop complicated mouth parts and sensory appendages if 00:23:57.253 --> 00:24:01.833 there was nothing there for them to actually supply information to. 00:24:01.833 --> 00:24:07.093 This was still the engine powering all these functional capabilities, right? 00:24:07.153 --> 00:24:10.253 So you could also argue, just to test out this idea, 00:24:10.513 --> 00:24:18.133 that evolution stumbled, if you want, into a brain prototype that suddenly facilitates 00:24:18.133 --> 00:24:22.473 the computational power to support all these different body machines. 00:24:22.713 --> 00:24:27.173 So you would not necessarily reject that interpretation. Not at all. Okay. 00:24:28.173 --> 00:24:34.053 But now the amazing thing that you also presented to us today is that you actually 00:24:34.053 --> 00:24:38.433 have found a way, if you want, to come up with sort of more direct evidence 00:24:38.433 --> 00:24:42.973 that evolution might have progressed in a very specific way, right? 00:24:42.993 --> 00:24:47.293 That we can go beyond conjecture, but actually look at what brains looked like 00:24:47.293 --> 00:24:51.413 during the Cambrian explosion, as opposed to having to speculate what they might have looked like. 00:24:51.753 --> 00:24:53.473 Yeah, I wouldn't say it progressed in 00:24:53.473 --> 00:24:57.653 a specific way. That's sort of too teleological for my taste. Thank you. 00:25:03.786 --> 00:25:09.226 Yeah, I wouldn't know really how to… I mean, clearly there was no progression, 00:25:09.406 --> 00:25:15.206 there was no internal engine that drove evolution. 00:25:17.246 --> 00:25:25.106 These things all occurred by accident and by selection depending upon their viability. 00:25:26.666 --> 00:25:33.406 So, yes, very early on the evolution gave rise to this thing we call the brain. 00:25:33.786 --> 00:25:41.046 The simple brain and that indeed allowed and its elaboration right um through process of of 00:25:41.286 --> 00:25:44.226 hit and miss evolution well let's just say change 00:25:44.226 --> 00:25:47.486 okay then if to keep it sort of neutral in that sense but 00:25:47.486 --> 00:25:51.586 i think that what was amazing was that you found a way to sort of travel back 00:25:51.586 --> 00:25:55.306 in time and try and direct evidence for whatever these changes were and i think 00:25:55.306 --> 00:25:59.546 this was really i think a very dramatic piece of evidence actually so maybe 00:25:59.546 --> 00:26:04.226 yeah you were lucky we were lucky so So maybe you can explain to us what was 00:26:04.226 --> 00:26:07.046 the question really that you were trying to answer and how did you answer it? 00:26:07.346 --> 00:26:13.246 The question derives from the cladistics that we were doing, 00:26:13.346 --> 00:26:16.646 trying to reconstruct phylogeners using brain characters. 00:26:17.006 --> 00:26:23.706 And it indicates that our results in this cladistic analysis indicated that 00:26:23.706 --> 00:26:27.246 branchia pods could not be the precursors of the insects and crustaceans. 00:26:27.286 --> 00:26:29.586 There must have been some kind of evolved loss. 00:26:31.086 --> 00:26:35.146 So, again, as I said in the talk, the only way to prove this is to go back in 00:26:35.146 --> 00:26:37.786 time and look at the early brains. Now, where did one find early brains? 00:26:37.926 --> 00:26:41.446 So, first of all, I went to the Smithsonian and looked through their fossil 00:26:41.446 --> 00:26:44.446 collection and found this one particular fossil that showed an early brain. 00:26:45.146 --> 00:26:47.786 But it wasn't really so satisfying. 00:26:48.766 --> 00:26:52.086 They were clearly very, very good optic lobes. It had very nice compound eyes. 00:26:52.286 --> 00:26:56.006 So, how can you see an early brain in a fossil? Because, I mean, 00:26:56.046 --> 00:26:59.026 the assumption most people have is that brains can't fossilize. 00:26:59.026 --> 00:27:00.246 Yes, but that is the assumption. 00:27:00.466 --> 00:27:07.566 And I never quite understood it because the brain is the most densely packed tissue in the body. 00:27:07.906 --> 00:27:11.686 You take an electromyograph through an insect brain or any brain, 00:27:11.786 --> 00:27:14.666 and it's packed, packed, packed, packed full of profiles. 00:27:15.146 --> 00:27:18.086 And these profiles have got lots and lots and lots of lipids. 00:27:18.086 --> 00:27:21.346 And inside there are lots of mitochondria and there's lots of iron. 00:27:21.346 --> 00:27:26.326 Iron, and it's a very bulky piece of tissue, 00:27:26.546 --> 00:27:31.166 and if you put that into quite reasonably anoxic conditions, 00:27:31.306 --> 00:27:37.506 it has a reasonable chance of surviving during mineralization. 00:27:38.746 --> 00:27:42.566 But there are very few taphinovic conditions that would allow this, 00:27:42.746 --> 00:27:48.546 and one is in the The Bird of Shale, as you know. And the other is in the Qingjiang Mudstone. 00:27:50.913 --> 00:27:57.813 So, that's where to go to. And you do see these trace internal organs, particularly gut. 00:27:58.993 --> 00:28:02.913 And gut's very popular amongst paleontologists. They love to say, oh, there's gut. 00:28:03.653 --> 00:28:08.233 But then you look in the head, in front of where the mouth was, 00:28:08.433 --> 00:28:10.573 and that could be gut diverticular. 00:28:10.773 --> 00:28:16.573 And indeed, in some specimens, you do have diverticular from the gut that invade the head capsule. 00:28:16.573 --> 00:28:22.713 But in others, you can clearly see the bundles, the nerves coming in from the 00:28:22.713 --> 00:28:30.533 antennae, the optic stalk tract going into a structure within the head capsule. 00:28:31.833 --> 00:28:35.713 And associated with that, you can also see ocelli, you can see the compound 00:28:35.713 --> 00:28:40.773 eyes and various other attributes, and also the paired nerve cords. 00:28:41.493 --> 00:28:45.933 And there you have then evidence of brain. So this is a fossil of an animal 00:28:45.933 --> 00:28:48.053 that lived 535 million years ago? 00:28:48.373 --> 00:28:53.053 Perhaps it was 500 or 500, the ones in the Qingchang in 535. 00:28:53.473 --> 00:28:56.913 And they're looking quite similar to some living animals? 00:28:57.253 --> 00:29:04.253 Yes, the ones from the Qingchang fauna, Fengxianhui, its brain is that of a 00:29:04.253 --> 00:29:10.693 modern malacostracan yes it has the three optic neuropills it has the fused ganglia uh. 00:29:12.473 --> 00:29:16.053 And its morphology the body morphology is incredibly simple, 00:29:17.033 --> 00:29:22.113 that's that's the fun part of it you have this you have this head capsule with 00:29:22.113 --> 00:29:26.453 eyes that clearly could move conjointly 00:29:26.453 --> 00:29:29.333 and convergently they could also rotate so you had active vision, 00:29:30.253 --> 00:29:34.473 You have different radii of curvature on the eye, so you had probably acute 00:29:34.473 --> 00:29:35.833 zones and non-acute zones. 00:29:37.213 --> 00:29:41.573 So that part of the head, this most frontal part of the head, 00:29:41.733 --> 00:29:45.773 was reasonably sophisticated, like that of a small shrimp. 00:29:46.693 --> 00:29:50.473 And it has the three optic neuropils one would expect from a small shrimp. 00:29:51.616 --> 00:29:55.456 But shrimps are very complicated. The rest of them are all these elaborations 00:29:55.456 --> 00:29:58.356 and spines and interesting appendages and so forth. 00:29:58.576 --> 00:30:04.236 Whereas Fu Xianhui has this homonymous architecture in the thorax and then again in the abdomen. 00:30:04.816 --> 00:30:08.836 And one would think, oh gosh, what a simple animal. But no, it's not. 00:30:09.016 --> 00:30:15.176 It must have been quite sophisticated in terms of what it could process up front. 00:30:16.276 --> 00:30:27.276 But it did have, let's say, a shrimp-like body. Well, it's a crustaceomorph, if you like. 00:30:27.336 --> 00:30:32.936 It's a stem taxon, which has attributes that one can see to more or less in 00:30:32.936 --> 00:30:39.076 some modern crustaceans. There's this ankyline species, they're called the remipedes. 00:30:41.816 --> 00:30:46.356 I forget how to pronounce this, it's got a wonderful name. 00:30:46.616 --> 00:30:51.336 This thing is homonymous, every single segment is identical except the first two segments up front. 00:30:51.616 --> 00:30:55.936 So it looks like a living fossil, but it's probably also undergone reversal and loss. 00:30:56.196 --> 00:30:59.996 If you look at the brain, it has a malacostric brain except It has no optic lobes. 00:31:01.836 --> 00:31:05.856 So it has a very superb brain with a very, very simple body. 00:31:06.316 --> 00:31:09.116 Fuxian Hui, which is very ancient, has a lovely brain with a very, 00:31:09.176 --> 00:31:12.976 very simple body. But that's probably not reduction and loss. 00:31:13.096 --> 00:31:14.256 That's probably for real. 00:31:14.516 --> 00:31:18.496 It's an animal. It has not reduced anything. It's a very early organization. 00:31:19.136 --> 00:31:23.336 But now in reconstructing this brain, all you can go for is, 00:31:23.436 --> 00:31:26.156 let's say, volumetric information, right? What is the size? 00:31:26.296 --> 00:31:31.116 What are the relative sizes of things? No, no, no. Volumetric is not really terribly interesting. 00:31:31.436 --> 00:31:35.956 What's interesting is to actually identify these centers, the three nested optic 00:31:35.956 --> 00:31:42.596 lobe centers, which are diagnostic of modern melacotricans and insects, but not of brachiopods. 00:31:42.756 --> 00:31:47.276 So it shows that this organization is the ancestral organization. 00:31:48.825 --> 00:31:51.365 Appeared before the branchiopods even appeared in the fossil record. 00:31:51.745 --> 00:31:56.445 And also you can actually show from the incoming nerve bundles in the antennae, 00:31:56.445 --> 00:31:59.825 from the second antennae, and from the eyes, that you have then three fused ganglia. 00:32:00.045 --> 00:32:02.945 Yes, so how did you identify exactly these three layers? 00:32:03.325 --> 00:32:06.485 The three bundles? Yes. The antennae are beautifully preserved, 00:32:06.765 --> 00:32:10.105 as are sensilla on the antennae. 00:32:10.285 --> 00:32:14.785 And then out of the antennae you have this beautiful, darkly brown, 00:32:14.925 --> 00:32:21.585 stained tract, which is the antennal nerve entering the outline of the brain. 00:32:21.945 --> 00:32:26.445 And just after the entry point, you have this area of rough preservation, 00:32:26.505 --> 00:32:31.205 which corresponds to the olfactory lobe position. Right. And that's bilaterally symmetrical. 00:32:32.345 --> 00:32:37.225 And then a little bit more cordially, you have another nerve entering, 00:32:37.365 --> 00:32:38.445 bilaterally symmetrical. 00:32:38.445 --> 00:32:41.365 Geometrical and that nerve um is um 00:32:41.365 --> 00:32:44.365 it then turns down and 00:32:44.365 --> 00:32:47.245 plunges down into the substrate into the matrix of the fossil 00:32:47.245 --> 00:32:52.725 uh and its direction is towards the the next pair of appendages of the second 00:32:52.725 --> 00:32:58.445 antennae so the um shrimp brain the modern shrimp brain is a lot like this very 00:32:58.445 --> 00:33:03.205 early animal brain but and you say the shrimp body is much more complicated 00:33:03.205 --> 00:33:05.905 does does that mean that a lot of the 00:33:06.245 --> 00:33:11.505 nervous system complexity that goes with that new body or change to the body 00:33:11.505 --> 00:33:14.505 is not in the brain, but it's in the other segments. 00:33:14.685 --> 00:33:19.245 I would, I think it's probably, certainly there are ascending pathways from 00:33:19.245 --> 00:33:25.025 the ganglia throughout the body that reach the brain in a shrimp and in an insect 00:33:25.025 --> 00:33:26.965 and probably in fuchsia and hui as well. 00:33:31.793 --> 00:33:36.873 It may be that some of the more complicated and more elaborate appendages of 00:33:36.873 --> 00:33:44.213 the shrimp, of the modern shrimp, send information that is required for cerebral computations. 00:33:45.553 --> 00:33:47.253 Tactile information, for example. 00:33:47.493 --> 00:33:51.973 And that would then involve maybe additional brain regions that have evolved 00:33:51.973 --> 00:33:58.733 through time, or maybe enlargement of regions that were already there in this ancestral brain. 00:33:58.833 --> 00:34:03.273 We have no idea. But when we compare across contemporary species, 00:34:03.433 --> 00:34:08.293 we can see certainly that the brain varies in size and in dimensions of certain regions, 00:34:08.593 --> 00:34:13.693 not because of actual attributes of the head, but with regard to attributes 00:34:13.693 --> 00:34:16.433 of the thoracic ganglion, abdominal ganglion. Right. 00:34:16.693 --> 00:34:21.513 But I mean, this idea of a distributed nervous system where within the segments, 00:34:21.733 --> 00:34:26.333 the local control, for instance, of an actuator system, a limb, 00:34:26.453 --> 00:34:28.053 is happening in that segment. 00:34:28.253 --> 00:34:33.373 And then the information that's ascending to the brain may be fairly limited 00:34:33.373 --> 00:34:35.293 compared to what's being sent to the segment. 00:34:35.353 --> 00:34:36.713 So you're just sending to the brain 00:34:36.713 --> 00:34:40.153 the information that's relevant to the decisions you might need to make. 00:34:40.713 --> 00:34:45.493 Well, yes, the reafferent pathways to the brain certainly will inform the brain 00:34:45.493 --> 00:34:48.313 about what is going on in the ganglion. 00:34:48.373 --> 00:34:52.833 One of the attributes of a dexterous insect, like, say, a praying mantis, 00:34:52.833 --> 00:34:54.273 is the ability to break symmetry. 00:34:55.493 --> 00:34:58.753 The circuits in each ganglion, of course, are symmetrical, and they provide 00:34:58.753 --> 00:35:01.593 symmetrical or at least alternating movements. 00:35:02.273 --> 00:35:07.813 To break that is a function of the brain. So, the brain is required to, 00:35:07.933 --> 00:35:13.573 if you like, receive information about the activity of those centers. Absolutely. 00:35:14.873 --> 00:35:24.653 So, the more elaborate, if you like, motor actions that are performed by the limbs, 00:35:24.953 --> 00:35:30.813 the more reafference one might expect reaching up to the brain into some of these higher centers. 00:35:33.956 --> 00:35:41.096 This kind of elaborate, dexterous behaviors amongst the crustaceans is quite limited, 00:35:41.216 --> 00:35:49.436 say, to the crabs and to some of the malacostracans, for example, the mantis shrimps. 00:35:50.016 --> 00:35:53.016 And interestingly, the mantis shrimp brain is very, very insect-like. 00:35:53.116 --> 00:35:57.156 It has centers that one would actually expect in a praying mantis. 00:35:57.296 --> 00:35:58.416 It's really fascinating. 00:36:00.296 --> 00:36:03.656 Whereas the shrimp brain, the shrimps, you know, they don't really have much 00:36:03.656 --> 00:36:06.536 dexterity except for two limbs. 00:36:08.476 --> 00:36:13.636 And most of the stuff is happening, I think, locally. Most of the motor coordination 00:36:13.636 --> 00:36:15.636 is happening locally without the participation of the brain. 00:36:16.056 --> 00:36:20.116 So I want to pursue a bit more this issue of similarity, right? 00:36:20.176 --> 00:36:23.916 Because here we have this fossil that's 535 million years old. 00:36:24.316 --> 00:36:26.836 And it looks like a modern shrimp, if you want. 00:36:28.156 --> 00:36:33.796 No, no, no. I mean the brain. The brain, yes. Okay. Yes. You already explained 00:36:33.796 --> 00:36:35.716 that the body is not identical. Very different, right. 00:36:36.476 --> 00:36:41.496 But still in terms of now, how specific can we get about the similarities of these brains? 00:36:41.656 --> 00:36:45.596 Like for instance, if you would look at, okay, now we have the antenna providing 00:36:45.596 --> 00:36:49.536 inputs to a deposit that matches something like an antenna lobe. 00:36:50.296 --> 00:36:54.356 Would you say that, let's say, the volume of that antenna lobe and the number 00:36:54.356 --> 00:36:57.816 of glomeruli that we could imagine would be also housed in that, 00:36:57.936 --> 00:37:03.016 or making up that antenna lobe, would be comparable to that what you would find 00:37:03.016 --> 00:37:04.656 in a matching, in a shrimp's brain? 00:37:05.156 --> 00:37:10.576 I think I would hesitate very, I would hesitate a very long time before I would 00:37:10.576 --> 00:37:12.756 try to do that kind of comparison. 00:37:15.004 --> 00:37:22.004 For no other reason that when you compare the optic, the olfactory lobes across 00:37:22.004 --> 00:37:28.724 different species of, even of malacostracans, of decapods even, 00:37:28.984 --> 00:37:37.804 then you have a lot of differences of packing of glomeruli, of sizes of glomeruli within the same volume. 00:37:37.944 --> 00:37:40.804 So I don't think I'm going to actually try that trick on fossils. 00:37:41.304 --> 00:37:46.184 So that then puts a boundary on, let's say, a similarity assessment you can make. 00:37:46.444 --> 00:37:48.724 Absolutely. Right, and I will try to understand that boundary. 00:37:48.944 --> 00:37:50.704 So where would you draw that boundary? 00:37:50.784 --> 00:37:58.024 Just, let's say, on core structure, the main neuropills making up this nervous system? 00:37:58.204 --> 00:38:04.164 I think, as I said, I think at the moment the boundaries would be to determine 00:38:04.164 --> 00:38:08.564 the number of segments involved in the brain. brain, if one is very lucky, 00:38:08.604 --> 00:38:11.804 the position of the olfactory lobes. 00:38:12.824 --> 00:38:20.724 If one's luckier, then perhaps proto-cerebral outgrowths, which might suggest a hemi-ellipsoid body, 00:38:21.284 --> 00:38:28.584 certainly the number of optic neuro-pills, and then the roots of the various 00:38:28.584 --> 00:38:31.784 nerves that invade the brain, and that's about it. Right, okay. 00:38:33.404 --> 00:38:36.724 So then what's the next step in this process? 00:38:37.264 --> 00:38:41.824 I mean, you're going after more fossils, I assume, right? Yes, 00:38:41.824 --> 00:38:46.524 so there is the question of the other brain. 00:38:46.824 --> 00:38:49.884 And the other brain is the brain that pertains to the chelicerates, 00:38:49.924 --> 00:38:55.864 which are the spiders, the scorpions, and their relatives, including Limulus, 00:38:55.924 --> 00:38:58.284 which is a very ancient morphology. 00:39:00.784 --> 00:39:04.484 Maybe we don't have time to go into all the nitty-gritty of why these brains 00:39:04.484 --> 00:39:06.684 look so very different than those of crustaceans and insects, 00:39:06.804 --> 00:39:07.804 but they are very different. 00:39:08.104 --> 00:39:11.444 Could you just mention a few outstanding, the most obvious differences? 00:39:11.484 --> 00:39:18.604 Well, the most obvious difference is the condensation of both the pre- and post-oral neuropills. 00:39:19.724 --> 00:39:24.164 So what has happened is that the first three segments of the brain are pretty 00:39:24.164 --> 00:39:28.344 much fused with the second, third, and fourth segments of the brain, 00:39:28.404 --> 00:39:30.264 which is subesophageal, which is post-oral, 00:39:30.444 --> 00:39:36.384 which are pretty much fused with the remaining ganglia, which have come together as one great lump. 00:39:37.964 --> 00:39:41.764 So at least the brain is a massive neuropoole with a hole through it for the 00:39:41.764 --> 00:39:45.404 gut. And it's very different from that of any crustacean or insect. 00:39:48.079 --> 00:39:54.259 Only spiders have evolved a visual system with three discrete centers. 00:39:55.919 --> 00:39:59.719 And these look very different from those of an insect. So there's a very nice 00:39:59.719 --> 00:40:02.479 example of convergent evolution, although these centers are already on the topic. 00:40:04.599 --> 00:40:09.919 So there are already major differences. So in the more basal chelicerae, 00:40:09.979 --> 00:40:13.559 we will never see three optic centers. 00:40:14.099 --> 00:40:18.759 So the goal then is to now find a fossil cell that can match that template, 00:40:18.959 --> 00:40:20.219 match that search image. 00:40:20.479 --> 00:40:26.059 But we know from things called sea spiders, pycnogonidae, their brains have 00:40:26.059 --> 00:40:31.519 all the neuro pills that are characteristic of the spider and chelicerae brains, 00:40:33.679 --> 00:40:36.619 which have got certain differences from those of crustaceans and insects. 00:40:36.919 --> 00:40:41.299 For example, the central body complex looks very different from all those of 00:40:41.299 --> 00:40:42.139 crustaceans and insects. 00:40:42.419 --> 00:40:46.539 So the pycnogonidae It has a spider brain, spider-like brain, 00:40:46.679 --> 00:40:48.139 but it has segmental ganglia. 00:40:48.219 --> 00:40:51.619 So it's the only chelicerae with segmental ganglia that's alive today. 00:40:52.219 --> 00:40:54.759 Limulus does have segmental ganglia, but there are very, very few of us. 00:40:56.519 --> 00:41:05.119 So we would look then for this spider-like brain plus segmental ganglia in something like Neuroi. 00:41:05.199 --> 00:41:09.039 And as I showed you today, Neuroi has, we have one specimen of Neuroi which 00:41:09.039 --> 00:41:14.459 we have very nice segmental ganglia preserved. We haven't got a neuroid which 00:41:14.459 --> 00:41:17.239 shows the brain yet, so that's the next target. 00:41:17.799 --> 00:41:22.799 Because the neuroids are supposed to be the stem group arachnomorphs, 00:41:22.799 --> 00:41:24.639 belong to the stem group arachnomorphs. 00:41:24.859 --> 00:41:29.099 So that would be fascinating to find the neuroid brain and show that it is actually 00:41:29.099 --> 00:41:33.079 very different from that of the crustacean morph brain, the Fuchsia and Hui brain. 00:41:33.719 --> 00:41:40.479 And then we'd have the other nervous system, the other branch of the arthropod. 00:41:40.479 --> 00:41:43.919 But what does the Neroid look like? What kind of animal? 00:41:44.159 --> 00:41:47.479 It's another very simple animal with a pair of antennae with a head shield and 00:41:47.479 --> 00:41:49.579 rather simple segments. 00:41:49.899 --> 00:41:54.519 It was probably much more ambulatorian, or rather not so much of a swimmer. We don't really know. 00:41:55.339 --> 00:42:03.019 But there are certain aspects which distinguish the Neroid from Fuchsian Hewitt. 00:42:03.019 --> 00:42:07.939 But there's so much ambiguity of these forms. 00:42:08.239 --> 00:42:10.239 I mean, you saw today Waptir. 00:42:10.679 --> 00:42:13.939 Waptee is this very strange animal, which, you know, there's a children's book 00:42:13.939 --> 00:42:16.619 called Animal Crackers. I used to have it when I was a kid. 00:42:17.079 --> 00:42:20.639 So you had pictures of animals that were cut in three pieces so you could actually 00:42:20.639 --> 00:42:24.499 mix and match. You could have a cat-o-goose or something like that. 00:42:25.239 --> 00:42:27.219 So Waptee looks like one of these, you know. 00:42:29.715 --> 00:42:32.535 Kangarillas um right we have 00:42:32.535 --> 00:42:36.495 bits of trilobite and bits of insect and bits of crustaceous all 00:42:36.495 --> 00:42:39.455 stuck together so it's very very hard to say well this 00:42:39.455 --> 00:42:42.415 must belong to this particular trajectory or that particular trajectory 00:42:42.415 --> 00:42:45.995 these two brains so one you identified the second one you're looking for we 00:42:45.995 --> 00:42:49.835 have the search image for exactly yeah so you would expect it also to be around 00:42:49.835 --> 00:42:55.495 500 million years old 535 million it's got to be the same okay it's got to be 00:42:55.495 --> 00:42:59.675 a co-evil exactly but then And then your suggestion is that these two brains 00:42:59.675 --> 00:43:02.055 are then one bifurcation removed from, 00:43:02.115 --> 00:43:04.095 let's say, the common ancestor brain. 00:43:04.295 --> 00:43:08.235 They were derived from a common ancestor somewhere deeper down. 00:43:08.575 --> 00:43:12.935 And that common ancestor, if you go far enough back, was also a common ancestor to us. 00:43:13.175 --> 00:43:18.555 Yes. And so what are the prospects of finding out more about the shared common 00:43:18.555 --> 00:43:20.775 ancestor between vertebrates and invertebrates? 00:43:22.115 --> 00:43:25.695 From the fossil record, I would be very pessimistic. but 00:43:25.695 --> 00:43:29.255 from modern molecular developmental biology 00:43:29.255 --> 00:43:32.475 there is already fabulous information 00:43:32.475 --> 00:43:35.355 about how you can rescue the forebrain say of 00:43:35.355 --> 00:43:39.775 a drosophila using a gene that's required for forebrain development in a mouse 00:43:39.775 --> 00:43:46.255 and vice versa homologous genes so the genetic evidence is that the head segmentation 00:43:46.255 --> 00:43:52.815 of flies and therefore of course crustaceans etc etc and those of mice therefore four cyclostomes, 00:43:52.915 --> 00:43:56.735 et cetera, et cetera, they derive from a common ancestor which has a tripartite brain. 00:43:58.015 --> 00:44:02.935 That is fascinating and it's really so exciting. People like Heinrich Reichardt 00:44:02.935 --> 00:44:08.115 and also Frank Heerth who have been involved in this work really deserve a lot 00:44:08.115 --> 00:44:11.775 of praise for bringing us to that level, 00:44:12.615 --> 00:44:13.835 of understanding, I think. 00:44:14.255 --> 00:44:17.755 Of course, there are still opponents of this. But that's an important point 00:44:17.755 --> 00:44:19.675 because you use this notion of tripartite brain, 00:44:20.435 --> 00:44:23.155 which was also used by people like mclean to 00:44:23.155 --> 00:44:26.015 say like the brain evolved in three stages but it's important 00:44:26.015 --> 00:44:28.775 to emphasize in this case that the three stages are there from the 00:44:28.775 --> 00:44:33.875 beginning well it maybe did evolve in three stages before before before the 00:44:33.875 --> 00:44:39.035 origin of these various trajectories it's possible we have you know right be 00:44:39.035 --> 00:44:43.935 a very different decomposition than one mclean imagined the same keyword i just 00:44:43.935 --> 00:44:46.315 wanted to sort of emphasize a little bit we're talking about but a different 00:44:46.315 --> 00:44:47.975 kind of tripartite scheme. 00:44:48.135 --> 00:44:51.635 He was talking about amphibians, reptiles, and mammals. 00:44:51.875 --> 00:44:55.315 Exactly. And then you sort of glued one module on top of the other. 00:44:55.795 --> 00:45:01.595 Yeah, that's, I think, um... Yeah, so it's not very... What we now know is that 00:45:01.595 --> 00:45:07.595 the history of this structure is very, very far back in the Cambrian and possibly 00:45:07.595 --> 00:45:08.815 in the pre-Cambrian times. 00:45:08.935 --> 00:45:13.075 Right, exactly. There's been a very lovely paper from Stan Grillner's lab earlier 00:45:13.075 --> 00:45:18.555 this year demonstrating that in the cyclostome, the organization of the basal 00:45:18.555 --> 00:45:21.715 ganglia is really no different from that in us. 00:45:22.275 --> 00:45:24.815 Right. I mean, these, these, these, these, these. 00:45:26.267 --> 00:45:34.307 These ground pattern organizations are the indicators of genealogical correspondence. 00:45:34.687 --> 00:45:39.127 And that's what one's looking for, to find what did the common ancestor really 00:45:39.127 --> 00:45:41.107 look like in terms of its neural organization. 00:45:41.667 --> 00:45:46.747 So Nick, this was a beautiful tour through the, let's say, evolution of the 00:45:46.747 --> 00:45:49.887 brain, trying to understand its origins. And so to conclude, 00:45:50.107 --> 00:45:51.347 there are two questions. 00:45:51.847 --> 00:45:55.567 Also, given your experience, trying to understand really the basic design of 00:45:55.567 --> 00:45:59.907 brains, what's the next Strauss-Feld law that we should adhere to? 00:46:00.487 --> 00:46:03.307 Strauss-Feld what? Law. Oh, I don't make laws. 00:46:04.467 --> 00:46:06.987 You're against law. Absolutely. Yes, yes, yes. 00:46:07.607 --> 00:46:11.987 Ideas, but not laws. It's a heuristics then, suggestion. As I said, 00:46:12.087 --> 00:46:19.367 you know, the next undertaking will be, well, I wear several hats, 00:46:19.547 --> 00:46:20.887 as you probably realize. 00:46:22.107 --> 00:46:28.167 The next undertaking with regard to the search will be the other brain, 00:46:28.327 --> 00:46:29.907 the arachnid type brain. 00:46:30.747 --> 00:46:34.007 That's one of the undertakings. But then my bread and butter research is on 00:46:34.007 --> 00:46:37.167 vision, so that's something else. That's something else, yeah. 00:46:37.347 --> 00:46:39.387 So now, in five years from now, we're going to go visit you, 00:46:39.447 --> 00:46:42.127 wherever you are on this planet, digging for fossils somewhere, 00:46:42.787 --> 00:46:45.767 and we're going to remind you of a hypothesis you're going to generate today, 00:46:46.027 --> 00:46:52.627 which is like, hey, Nick, you predicted September 2012 that X would be valid 00:46:52.627 --> 00:46:54.707 in our understanding of the brain. 00:46:54.767 --> 00:46:57.127 So what's that hypothesis you feel most strongly about today? 00:46:57.647 --> 00:47:02.467 Well, I think, as I said, I think there are two, there's two evolutionary trajectories 00:47:02.467 --> 00:47:05.287 giving rise to these two major groups of arthropods. 00:47:07.007 --> 00:47:13.487 The chelicerates and the others, the mandibulates, all these wonderful body 00:47:13.487 --> 00:47:17.987 forms one sees throughout the history of evolution, they're like decorations 00:47:17.987 --> 00:47:19.467 on two kinds of Christmas tree. 00:47:19.967 --> 00:47:24.087 You have the same kind of Christmas tree for, you have one species like a spruce, 00:47:24.287 --> 00:47:28.807 beautiful branch Christmas tree for the trajectory leading to insects and crustaceans, 00:47:28.827 --> 00:47:31.867 another kind of tree to which it chelicerates. 00:47:31.947 --> 00:47:35.767 Then you hang different kinds of baubles every Christmas on these trees, right? 00:47:36.387 --> 00:47:39.047 And then each Christmas you have a different species, but the actual, 00:47:39.167 --> 00:47:42.187 the basic structure inside is the same throughout, it's a continuum. 00:47:42.527 --> 00:47:46.907 And we hang again off another tree. Right, right. Okay, Nick Straschl, 00:47:46.967 --> 00:47:49.487 thank you very much for this conversation. You're very welcome. 00:47:48.400 --> 00:47:54.320 Music. 00:47:53.787 --> 00:47:59.367 The CSN Podcast was produced by the Convergent Science Network of Biometrics 00:47:59.367 --> 00:48:06.027 and Biohybrid Systems, a project funded by the European Sevens Research Framework Programme. 00:48:06.160 --> 00:48:34.115 Music.