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Bill Hansson on insect olfaction and antennal lobe

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Season 2011
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How do flowers deceive insects into pollinating them , and what does this reveal about how olfactory systems encode meaning? Bill Hansson explores the evolutionary arms race between plants and pollinators through the lens of insect chemosensory neuroscience. Subscribe for more from the Convergent Science Network podcast series. Bill Hansson studies olfaction in insects, and his entry point is one of nature’s most elaborate deceptions. One-third of all orchid species are deceptive , they attract pollinators without offering nectar rewards, instead mimicking the chemical signatures of food, mates, or egg-laying sites with extraordinary precision. Hansson describes flowers that replicate the individual odor variation of female bees so accurately that males never learn to avoid them, and Mediterranean lilies that mimic both the volatile chemistry and the elevated temperature of rotting flesh to lure egg-laying flies into their chambers. These deceptive systems serve as powerful experimental tools. Because evolutionary pressure demands that the mimicry be nearly perfect, deceptive flowers effectively reveal which chemical features matter most to the insect brain. Hansson’s laboratory uses this insight in reverse: by identifying the behaviorally relevant compounds through the deception, they can probe the olfactory system with precisely the stimuli it evolved to detect. The approach has been transformed by advances in single-neuron electrophysiology and optical imaging of the antennal lobe , the insect brain’s first olfactory processing center. A surprising finding emerges from comparing input and output patterns in the Drosophila antennal lobe. At the receptor neuron level, there is no clear clustering of activation patterns by behavioral valence , attractive and repulsive odors look similar. But at the projection neuron output, attractive and repulsive patterns separate cleanly. This suggests the antennal lobe performs a valence-sorting operation, not just odor discrimination, before information even reaches the mushroom bodies traditionally associated with learning and memory. Hansson speculates that this early valence coding may serve the direct pathway to the lateral horn, which bypasses the mushroom bodies entirely and may mediate reflexive behavioral responses. The interview also examines a remarkable case of evolutionary specialization in Drosophila sechellia, a species that feeds exclusively on a single toxic fruit. This fly has sacrificed several receptor types used by its generalist relatives and massively expanded both the peripheral neurons and the central brain regions dedicated to detecting its host fruit , achieving detection thresholds rivaling moth pheromone systems at picogram concentrations.

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Both the triumphs of humanity and its most evil deeds have resulted from collaboration. In a time where humanity is required to aspire to the former and minimize the latter, the question arises of how collaboration arises and why it fails. Surprisingly, this phenomenon, so central to who we are, is not well understood. Hence, a collaborative effort is required to understand collaboration in its full biological, psychological, sociological, cultural, and economic complexity and to translate this understanding into operational impact. This series of podcasts is one step toward achieving these complementary goals. The Collaboration Podcast presents interviews with people who are central orchestrators of collaboration in various domains including business, government, science, art, health, sustainability, and the military. The discussions were conducted by Prof. Dr. Paul F.M.J. Verschure and members of the Program Advisory Committee of the Ernst Strungmann Forum on Collaboration (https://www.esforum.de/forums/ESF32_Collaboration.html) during 2021 and had the goal to sketch a map of opportunities, challenges, and obstacles in human collaboration. The forum took place in May 2022, and now we would like to share this series of interviews with a broader audience. The full report of the Forum will be published in 2023 by MIT Press. The podcast was produced by the Convergent Science Network (https://www.convergentsciencenetwork.org/). Context: The stability of social systems depends critically on realizing sustainable methods of “collaboration,” yet how and by which means collaboration is achieved is not clearly understood; neither are the conditions or processes that lead to its breakdown or failure. Collaboration can be understood as cooperation between agents toward mutually constructed goals. Part of the reason for our lack of understanding is that the phenomenon of collaboration is, by nature, a highly multidisciplinary problem, and effective research into its complexities has been difficult to achieve across the broad range of scientific and technical disciplines involved. The need for a fundamental understanding of collaboration, however, has become increasingly important. Not only does humankind demand answers as it attempts to address critical challenges at multiple scales (e.g., climate change, migration, enhanced automation, social and economic inequality), but ever-increasing technological and economic means of interconnecting people and societies are disrupting long-established, familiar patterns of how we interact. Radical technological changes that are ongoing have the potential to reshape collaboration in ways that are currently hard to predict or influence (e.g., by altering configurations in interaction, information creation, and modes of communication). On one hand, such changes could disrupt hitherto stable forms of collaboration by affecting critical communication channels and traditional roles, as can be observed in the rapidly changing patterns in governance, commerce, and social interaction. Conversely, technology could lead to the emergence of novel, successful forms of collaboration that deviate from traditional “hierarchical” architectures. Evidence of this can be seen in areas as diverse as highly automated manufacturing plants, the open science movement, collaborative software repositories, user-centered services, and the sharing of economy-based modes of organization. Without a fundamental understanding of the mechanisms, processes, and boundary conditions of collaboration, it is not possible to evaluate or predict which of these possible scenarios are sustainable or even plausible. The Forum “How Collaboration Arises and Why it Fails” (May 8–13, 2022, Location: Frankfurt am Main, Germany) Chairs: Andreas Roepstorff and Paul Verschure Program Advisory Committee: Jenna Bednar, Julia R. Lupp, Bhavani R. Rao , Andreas Roepstorff, Ferdinand von Siemens, and Paul Verschure

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  • fast_forward00:00:00 - This is Paul Foucher, the Conversion Science Network, talking to Bill Hansen.
  • fast_forward00:00:06 - Bill organized a conference on evolution of olfaction. We happen to be on Christmas Island.
  • fast_forward00:00:13 - So Bill, why did you choose olfaction as an entry point into the evolution of sensory systems?
  • fast_forward00:00:22 - I think it's a cool system.
  • fast_forward00:00:25 - That's the first thing in general. And I also think it's extremely important
  • fast_forward00:00:30 - for many of the animals that we have chosen to work on.
  • fast_forward00:00:33 - So I mainly work on insects and then they are very smelled ribbon as far as I see it.
  • fast_forward00:00:39 - And this has made their olfactory sense evolve in different ways.
  • fast_forward00:00:47 - And we find different themes, both peripherally and centrally,
  • fast_forward00:00:53 - where they have gone in different directions.
  • fast_forward00:00:57 - And as I also mentioned in my talk, that we also find these systems that exploit
  • fast_forward00:01:03 - the insect olfactory system in different ways.
  • fast_forward00:01:07 - And there we have like co-evolution going on, which is also very interesting
  • fast_forward00:01:11 - how exquisite one system can exploit another one to dupe other organisms to
  • fast_forward00:01:21 - do what they want them to do.
  • fast_forward00:01:24 - Right, but now you're jumping ahead of it, right?
  • fast_forward00:01:26 - Because in your talk, you made this point that actually the way we look at olfactory
  • fast_forward00:01:31 - systems has sort of changed,
  • fast_forward00:01:33 - that we have initially taken more of this view of, okay, let's just look at
  • fast_forward00:01:39 - these receptors, let's see what they tell us about the world,
  • fast_forward00:01:42 - let's see what they tell us about the stimuli that we're processing,
  • fast_forward00:01:45 - and now this whole process seems to have reversed, if you want.
  • fast_forward00:01:50 - So can you say something about this change? change yeah that there was also
  • fast_forward00:01:54 - a little bit about the methodologies that we use so we have.
  • fast_forward00:01:58 - We we started off with having a lot of we knew
  • fast_forward00:02:01 - something about the olfactory system but not very much so
  • fast_forward00:02:04 - what we knew was more or less that we could we could record a signal and we
  • fast_forward00:02:09 - could use this signal to tell us something about what insects or other organisms
  • fast_forward00:02:14 - met so therefore we We used the system as such as a detector for interesting odors.
  • fast_forward00:02:22 - And we used it to identify the odors. And this way we could see,
  • fast_forward00:02:25 - for instance, how have pheromone systems evolved.
  • fast_forward00:02:29 - And then we could identify what one moth smells, and then the closely related
  • fast_forward00:02:34 - moth smells, and the less closely related moth smells.
  • fast_forward00:02:37 - And we could draw phylogenetic and evolutionary conclusions.
  • fast_forward00:02:41 - Now, I think during the last decade, this has turned around a bit.
  • fast_forward00:02:46 - So now we know a lot of the natural things that insects and other organisms detect.
  • fast_forward00:02:52 - And now we use that to probe the olfactory system.
  • fast_forward00:02:56 - So we take the reverse entry in.
  • fast_forward00:03:00 - So we go in from the chemicals where we know that, for instance,
  • fast_forward00:03:04 - a fruit fly likes a certain substrate. Okay, then we can use that substrate
  • fast_forward00:03:08 - by using state-of-the-art chemistry.
  • fast_forward00:03:12 - We can identify what these compounds are, and then we can go into the olfactory
  • fast_forward00:03:17 - system, and we can look at what part of the olfactory system is tuned to detect
  • fast_forward00:03:22 - these different compounds.
  • fast_forward00:03:24 - So we can sort of dissect the system by odors before we dissect the odors by
  • fast_forward00:03:31 - the system. Yeah, but this seems almost circular now, because this only seems
  • fast_forward00:03:36 - to make sense if you really know what these odors are about.
  • fast_forward00:03:39 - How do you then ground this understanding? I mean, it doesn't mean that you
  • fast_forward00:03:43 - have a full understanding of the chemical composition of what we call an odor,
  • fast_forward00:03:47 - and therefore you can interpret this.
  • fast_forward00:03:49 - That's what's good about insects, because we know a lot of different things.
  • fast_forward00:03:53 - So the first thing that people started dissecting were the pheromones.
  • fast_forward00:03:57 - So in 1959, Butanant identified the first silk moth pheromone,
  • fast_forward00:04:02 - what we call by using half a million females.
  • fast_forward00:04:05 - Today, we can use more or less one female and one male and get to the chemical
  • fast_forward00:04:10 - identity of this pheromone.
  • fast_forward00:04:12 - And by then using that one, we can go into the receptor families and try to
  • fast_forward00:04:16 - pull out which receptor is tuned to these different compounds.
  • fast_forward00:04:21 - But also, as I said before, one of my favorites is to use deceptive systems.
  • fast_forward00:04:27 - Because if you want to deceive someone and you want that to be a stable deception
  • fast_forward00:04:31 - evolutionarily, you have to be really, really good because it's a constant Red Queen race.
  • fast_forward00:04:38 - So if you're a flower...
  • fast_forward00:04:41 - And you don't want to pay your pollinator with nectar, which is pretty expensive.
  • fast_forward00:04:46 - It's sugar, constant production.
  • fast_forward00:04:48 - Then you have to smell so good that the other guy, he cannot say no, he will come.
  • fast_forward00:04:53 - So therefore, in many, many flowers, this has developed.
  • fast_forward00:04:56 - We think of it sometimes as deception, but I find now the more I look at it,
  • fast_forward00:05:02 - that if you really go into the literature, one of the biggest families,
  • fast_forward00:05:06 - for instance, that we have of plants is orchids.
  • fast_forward00:05:08 - And one third of the orchids are deceptive.
  • fast_forward00:05:11 - So they have all invented ways
  • fast_forward00:05:14 - of fooling insects to think that they are something else than they are.
  • fast_forward00:05:19 - And now also in your own research here, you went through a number of stages, right?
  • fast_forward00:05:23 - Because I think you were the first who highlighted this deception using,
  • fast_forward00:05:29 - let's say, the smell of rotting meat.
  • fast_forward00:05:32 - This was sort of the entry point in this whole issue of deception.
  • fast_forward00:05:36 - And now that story has advanced quite a bit, also using very different kinds of technologies.
  • fast_forward00:05:41 - So can you say something about that evolution of your own work in this area of deception?
  • fast_forward00:05:47 - Well, what we actually started with was orchids. That was when we were still
  • fast_forward00:05:51 - working on pheromones a lot and trying to understand the olfactory background to pheromones.
  • fast_forward00:05:56 - And then we found these flowers that are really super mimicking bee pheromones
  • fast_forward00:06:02 - to dupe bees to pollinate them.
  • fast_forward00:06:06 - This was the collaboration with our Austrian colleagues. And that system is
  • fast_forward00:06:11 - just as amazing as anything else.
  • fast_forward00:06:13 - And it was a good starting point on this whole journey because these flowers,
  • fast_forward00:06:17 - they do very intelligent insects, intelligent within Cytacean Mark.
  • fast_forward00:06:23 - But I mean, a male bee of this species, the female will only mate with the male once.
  • fast_forward00:06:30 - And each female has a unique odor. order. So when the male has mated with this
  • fast_forward00:06:34 - female, he learns the order of that female and he will not go back to her because
  • fast_forward00:06:38 - he knows that he will not be allowed to mate once more.
  • fast_forward00:06:44 - Analogously if every flower that
  • fast_forward00:06:48 - were mimicking these odors smelled the
  • fast_forward00:06:50 - same the male would also learn the odor of that
  • fast_forward00:06:53 - flower and would never go back so what does
  • fast_forward00:06:56 - the flower do it mimics exactly the variation that
  • fast_forward00:06:59 - you have between the females within these bees and in
  • fast_forward00:07:03 - this way dupe the males to to go back
  • fast_forward00:07:06 - and and to try complex how complex is
  • fast_forward00:07:09 - this variation chemically but it's a 10 compound found
  • fast_forward00:07:12 - paramount and and there are three
  • fast_forward00:07:16 - or four of these that vary in proportions to
  • fast_forward00:07:19 - to a certain extent and in this way they they get these individual signatures
  • fast_forward00:07:23 - so that's more or less where we started but then we got into these flowers that
  • fast_forward00:07:28 - smell that's what we call sexual mimicry right but then we have the the brood
  • fast_forward00:07:34 - site mimicry and that's where we got more and more
  • fast_forward00:07:37 - interesting because in the first one you dupe males to
  • fast_forward00:07:40 - go for sex in the second one you dupe females
  • fast_forward00:07:43 - to go for a place to lay their eggs and that's
  • fast_forward00:07:47 - where we started on the the sardinian flowers that smell like rotten meats and
  • fast_forward00:07:53 - and we first we observed the system and we saw that flesh-eating flies were
  • fast_forward00:07:58 - attracted and what we found in the end was that these flowers mimic exactly
  • fast_forward00:08:02 - in the order of rotting flesh to attract flies.
  • fast_forward00:08:06 - But not only that, but they also mimic the increased temperature of a rotting body.
  • fast_forward00:08:13 - So the flower increases more than 15 degrees above ambient temperature to actually
  • fast_forward00:08:18 - attract the flies into itself.
  • fast_forward00:08:20 - So the odor is a long-range attractant, and then the temperature is the short-range
  • fast_forward00:08:25 - attractant that makes the fly really go into it.
  • fast_forward00:08:28 - So it's a multi-sensory deception.
  • fast_forward00:08:32 - Okay. But then in this case, this is all assessed at the behavioral level.
  • fast_forward00:08:38 - Well, basically sitting there and looking at this long enough and seeing what
  • fast_forward00:08:42 - the flies do, what the insects do.
  • fast_forward00:08:45 - No, we could never have done that without having access to the olfactory system. Okay.
  • fast_forward00:08:50 - First, we saw the behavior in the field, but then we used the olfactory system
  • fast_forward00:08:55 - of the bee, of the fly, and so on and so forth, to really pinpoint which odors are the active ones.
  • fast_forward00:09:02 - So we could never have done that without the biological system as a detector.
  • fast_forward00:09:07 - So which aspects of the system did you look at at that stage?
  • fast_forward00:09:09 - This was the first stage, so we only looked at the sound potentials,
  • fast_forward00:09:14 - which is called an electroantenogram.
  • fast_forward00:09:16 - So you look up the antenna of an insect, and then you kind of record like an
  • fast_forward00:09:22 - EKG or an EEG, but here we call it an EEG.
  • fast_forward00:09:26 - And on the antenna, essentially, you have the receptors that would be sensitive
  • fast_forward00:09:29 - to different aspects of these molecules. Just like in your nose,
  • fast_forward00:09:33 - you have thousands and millions of receptors on an insect antenna.
  • fast_forward00:09:38 - An insect antenna is like an inside-out nose.
  • fast_forward00:09:41 - So there are the receptors sitting on the outside, constantly exposed to the surrounding.
  • fast_forward00:09:47 - So how is that work advanced now? Because sometimes also in your presentation,
  • fast_forward00:09:51 - you try to show that you have now much more also electrophysiological access
  • fast_forward00:09:55 - to the system, and to also more specifically pinpoint,
  • fast_forward00:09:59 - let's say, the neuronal correlate, if you want, of the chemical structure of
  • fast_forward00:10:04 - the specific volatile molecules that you might be interested in.
  • fast_forward00:10:07 - So what has been the advance there?
  • fast_forward00:10:11 - So, EAGs have been the methodology of choice for many, and it's something that anyone can do.
  • fast_forward00:10:17 - So, it's today a general method in any lab working on insect semiochemicals.
  • fast_forward00:10:23 - But then we have now progressed.
  • fast_forward00:10:25 - So, now we go in and make recordings from single neurons on the antenna,
  • fast_forward00:10:30 - and then you gain sensitivity and specificity.
  • fast_forward00:10:34 - But at the same time of course you lose the wide scope of the EEG because in
  • fast_forward00:10:41 - the EEG you will get peaks more or less for every compound that the antenna
  • fast_forward00:10:45 - detects but the question is then,
  • fast_forward00:10:50 - do you get every compound and that's probably not true but if you go for single
  • fast_forward00:10:55 - neurons then you increase the sensitivity to such a degree that you really detect
  • fast_forward00:11:01 - more or less everything that that single neuron detects
  • fast_forward00:11:04 - but you also gain a lot of information on the system per se because you gain
  • fast_forward00:11:11 - information exactly on what a specific receptor is tuned to detect it.
  • fast_forward00:11:16 - But in this case, you're still stuck, if you want, at the level of single receptor neurons.
  • fast_forward00:11:25 - Yes. So if the encoding of the compound, the overall compound,
  • fast_forward00:11:28 - would require multiple receptor neurons, how can you access that information?
  • fast_forward00:11:32 - Information, can you perform multiple recordings simultaneously on this system now?
  • fast_forward00:11:37 - The first way to get at that is, of course, to make exhaustive studies of the whole antenna.
  • fast_forward00:11:42 - And that's what we've actually been doing. So you record from hundreds of neurons.
  • fast_forward00:11:47 - Consecutively, not at the same time, but you probe and you run and you probe and you run.
  • fast_forward00:11:52 - And in this way, we have actually mapped out more or less the full system of an insect,
  • fast_forward00:11:57 - like the mosquitoes for instance we have really done very
  • fast_forward00:12:01 - very exhaustive screenings but what i
  • fast_forward00:12:04 - guess you're getting at is the next level where we can where
  • fast_forward00:12:07 - we can open the brain of the insect and we can image the first relay center
  • fast_forward00:12:13 - in the brain which is the antenna lobe where you have the glomeruli and each
  • fast_forward00:12:17 - glomerulus represents input from a certain receptor type and there we can and
  • fast_forward00:12:23 - stimulate the antenna with the output of the gas chromatograph,
  • fast_forward00:12:27 - and then we can see how different glomeruli light up in the brain of Drosophila, for instance.
  • fast_forward00:12:33 - And in several species, we have such a good map of the brain,
  • fast_forward00:12:36 - a constant map that is invariant, that we can map certain receptors to exactly
  • fast_forward00:12:43 - the specific glomerulus that is activated.
  • fast_forward00:12:48 - So we know that if this glomerulus lights up, Well, that means that the receptor
  • fast_forward00:12:53 - 69A is activated on the antenna.
  • fast_forward00:12:56 - But now, let's take Drosophila as our example, right?
  • fast_forward00:13:00 - So what's the odour space that these insects live in? How complex is this odour space?
  • fast_forward00:13:08 - I think it is not as complex as ours. We have 200-300 active receptors.
  • fast_forward00:13:15 - They are playing around with 50-60.
  • fast_forward00:13:18 - So, I mean, it will be more reduced, but still they can encode an enormous amount of odors.
  • fast_forward00:13:24 - And, I mean, if you look at all these receptors and the combinatorial coding
  • fast_forward00:13:32 - that you can get between them and by getting a few or more activated and so
  • fast_forward00:13:37 - on, still already by having 60,
  • fast_forward00:13:39 - you can code an immense amount.
  • fast_forward00:13:42 - So in terms of real, let's say, olfactory objects, how big would that space be for Drosophila?
  • fast_forward00:13:49 - Dozens, hundreds, thousands?
  • fast_forward00:13:51 - No, come on. We say that with our receptors, 200, 250 active ones,
  • fast_forward00:13:57 - we can code an innumerable number of orders.
  • fast_forward00:14:00 - And so it's more or less the same answer
  • fast_forward00:14:04 - for drosophila they can more or less
  • fast_forward00:14:06 - code any odor that they are exposed to yeah the base in theory right if we say
  • fast_forward00:14:11 - all possible combinations of receptor neurons are being used and that's that
  • fast_forward00:14:15 - space would be very large but do we know behaviorally that also that that's
  • fast_forward00:14:20 - that size of of encoding space is really being used or.
  • fast_forward00:14:26 - Well you're getting into very uh interesting also evolutionary questions there
  • fast_forward00:14:32 - because i mean of course they have a specific repertoire of behaviorally relevant
  • fast_forward00:14:38 - odors that mean something to them and that's where that's where we got an instep
  • fast_forward00:14:43 - into this system by using our latest.
  • fast_forward00:14:46 - Devious flower as well because we find that this flower is targeting different receptor
  • fast_forward00:14:51 - populations that mean specific things to the fly to
  • fast_forward00:14:54 - the fly so which which flower is that that's the
  • fast_forward00:14:56 - solomon's lily in the north of israel aaron palestina
  • fast_forward00:15:00 - and this one dupes drosophila to pollinate it without reward and what we found
  • fast_forward00:15:06 - is that it's really hitting three types of receptors one type is saying that
  • fast_forward00:15:12 - here is fermentation going on one type says that it's It's fruit going on here. This is fruit.
  • fast_forward00:15:18 - And then the third one says that this is exactly your type of fruit that you
  • fast_forward00:15:22 - like. So it's really like a three-step rocket.
  • fast_forward00:15:25 - And it's probably not mimicking one specific thing.
  • fast_forward00:15:28 - Uh substrate but it's collecting super attractive
  • fast_forward00:15:32 - parts of several different stimuli
  • fast_forward00:15:36 - to build up an image of
  • fast_forward00:15:39 - something that the fly cannot say no to no because why am i asking why i wanted
  • fast_forward00:15:43 - us to agree a little bit on on let's say the the magnitude of this of this olfactory
  • fast_forward00:15:49 - space because this this should constrain a bit our questions around the the
  • fast_forward00:15:54 - antenna lobe itself Because in the end,
  • fast_forward00:15:57 - if we go from our receptor neurons through our antenna lobe,
  • fast_forward00:16:01 - sort of in that interaction,
  • fast_forward00:16:02 - the encoding of this effective olfactory space should happen, I would assume.
  • fast_forward00:16:08 - So then what does the antenna lobe really contribute to this process?
  • fast_forward00:16:13 - Because now you're saying, I can just look at these combinations of receptor
  • fast_forward00:16:16 - responses and actually with that already I can tell you what I'm sensing out
  • fast_forward00:16:22 - there in the world. So what's the antenna lobe really adding to this process?
  • fast_forward00:16:28 - Well, I think the antenna lobe adds balance. So we definitely can tell what
  • fast_forward00:16:33 - the receptor neurons detect by looking at activations of glomeruli.
  • fast_forward00:16:39 - But as you know, with rosophila, we have the possibility to encode genetically
  • fast_forward00:16:44 - our markers at any level.
  • fast_forward00:16:47 - So we can encode one marker at the input part of the antenna lobe,
  • fast_forward00:16:53 - and we can encode another marker at the output.
  • fast_forward00:16:56 - And we can compare these two activations.
  • fast_forward00:16:59 - And then we see that there are definitely things happening in the antenna lobe.
  • fast_forward00:17:04 - So if, for instance, we have done a very large screening of synthetic odors that we know are.
  • fast_forward00:17:11 - Positive for the fly so they will go for them in
  • fast_forward00:17:14 - a bioassay and then we have other orders that
  • fast_forward00:17:17 - are that are negative so they will not definitely not
  • fast_forward00:17:20 - they will go away from them and what we find when
  • fast_forward00:17:23 - we look at the input only we don't find any
  • fast_forward00:17:26 - correlation among patterns and the balance of the orders but when we look at
  • fast_forward00:17:33 - the output of the antenna lobe we found very nice clustering of of of patterns
  • fast_forward00:17:40 - that are encoding attractivity and patterns that are encoding repulsion.
  • fast_forward00:17:46 - So there is definitely something going on in there that is sharpening the balance
  • fast_forward00:17:53 - of the message that is coming. So not the discrimination then?
  • fast_forward00:17:56 - So in this case you're clustering data from the projection neurons or from the
  • fast_forward00:18:00 - glomeruli, from optical imaging?
  • fast_forward00:18:03 - Yes, we are doing optical imaging of both the input, so the receptor neuron
  • fast_forward00:18:08 - input into the glomeruli, and then we're doing optical imaging of the projection neuron patterns.
  • fast_forward00:18:15 - So in the same fly, you can do both, but using different kinds of dives.
  • fast_forward00:18:22 - Or you can do it in different fly circles. Sure, of course. But I mean,
  • fast_forward00:18:24 - you can clearly separate what is encoded in the input and what is going out of the system.
  • fast_forward00:18:32 - And then we know that in between there are these large local interneurons that
  • fast_forward00:18:38 - are shuffling messages between the glomeruli.
  • fast_forward00:18:41 - So are you saying that then the glomeruli are just performing some transformation
  • fast_forward00:18:46 - from an odor space into a balance space?
  • fast_forward00:18:49 - In some way, that's what we're seeing right now, that there seems to be something
  • fast_forward00:18:53 - going on that gives meaning to these orders.
  • fast_forward00:18:58 - This is really very interesting, but also a bit, in some sense, counterintuitive, no?
  • fast_forward00:19:04 - Because we have this projection that's going to the mushroom bodies that many
  • fast_forward00:19:08 - people have talked about, that have been, let's say, really very much involved
  • fast_forward00:19:10 - in associative learning and especially also valence-driven learning.
  • fast_forward00:19:14 - So how should we now compare this interpretation to this more standard view
  • fast_forward00:19:18 - on this happening at the level of the mushroom bodies?
  • fast_forward00:19:21 - No, but I think there is an initial sorting, and then this gets refined as they move up the system.
  • fast_forward00:19:28 - And then you have the two pathways. If you know the insect system,
  • fast_forward00:19:33 - you know that there is one pathway that goes from the antenna lobe to the mushroom
  • fast_forward00:19:36 - body, and then it goes out into the lateral protocephalogram.
  • fast_forward00:19:40 - But then we have one that totally bypasses the mushroom bodies and goes direct
  • fast_forward00:19:44 - to the lateral horn or the lateral crotocerebral.
  • fast_forward00:19:50 - And there we think that these two pathways are mediating different things.
  • fast_forward00:19:56 - One is taking the road over the conscious center of the insect brain and then
  • fast_forward00:20:05 - going out to maybe the executive center.
  • fast_forward00:20:07 - But one path is going directly to the executive.
  • fast_forward00:20:11 - And i think our feeling is that maybe
  • fast_forward00:20:14 - this maybe this is extremely important especially for
  • fast_forward00:20:17 - this reflexive pathway so that you need a
  • fast_forward00:20:20 - sorting already here to tell the reflexive pathway
  • fast_forward00:20:23 - what is going on yeah it would still be strange i mean i'm a bit confused now
  • fast_forward00:20:27 - because in some sense it would mean that if if my output from my from my antenna
  • fast_forward00:20:32 - load processing is just if you want good or bad um the balance of of the stimuli
  • fast_forward00:20:37 - i'm dealing with and i lose my discrimination determination abilities i cannot
  • fast_forward00:20:40 - say anymore whether it was an apple or an orange.
  • fast_forward00:20:43 - You would expect that also for let's say your
  • fast_forward00:20:46 - behavior this might be rather unspecific yeah but
  • fast_forward00:20:49 - i don't i that's going too far i think because because it yeah it seems like
  • fast_forward00:20:54 - you have clusters so so within each cluster of of there might be 15 glomeruli
  • fast_forward00:21:00 - so one saying apple one saying orange one saying pineapple one saying banana
  • fast_forward00:21:05 - and and i mean but but it seems like what
  • fast_forward00:21:08 - we're finding is that these that say something good,
  • fast_forward00:21:11 - and sort of take part in the combinatorial coding of something that is good.
  • fast_forward00:21:16 - They seem to be in some way clustered and have become clustered during evolution.
  • fast_forward00:21:21 - And the glomeruli, maybe also 10 or 15, that are saying that something is bad,
  • fast_forward00:21:26 - they have also become clustered in another way.
  • fast_forward00:21:29 - And this makes it possible for us by principal component analysis to say, to predict.
  • fast_forward00:21:36 - Was this pattern, was this activation pattern in the antenna lobe,
  • fast_forward00:21:41 - for a an attractive odor or was
  • fast_forward00:21:44 - it for a repulsive all right so you're saying
  • fast_forward00:21:47 - it's like a multidimensional code it's something like on the
  • fast_forward00:21:50 - one hand it will tell you what it is like this is a banana and it's good yeah
  • fast_forward00:21:55 - or this is some acid and it's bad so it will tell you both yeah all right so
  • fast_forward00:22:00 - but why at the level of the antenna also from an evolutionary and behavioral
  • fast_forward00:22:04 - perspective it seems counterintuitive that already at this early processing stage we start to label.
  • fast_forward00:22:10 - Stimuli with respect to valence or not do you
  • fast_forward00:22:13 - find this intuitive i i don't find
  • fast_forward00:22:16 - it so counterintuitive because if we we
  • fast_forward00:22:20 - think that the system has evolved by by glomeruli splitting and forming new
  • fast_forward00:22:26 - ones you know you have the evolution of a receptor by a mutation of a previous
  • fast_forward00:22:31 - existing one and this adds a new glomerulus in in the antenna so this means that
  • fast_forward00:22:37 - maybe you had one detecting something,
  • fast_forward00:22:40 - a good fruit of some kind, but then you got a refinement that was evolutionarily
  • fast_forward00:22:45 - advantageous, that they could detect another kind of fruit,
  • fast_forward00:22:50 - that might be good to separate from the ones they knew already before.
  • fast_forward00:22:55 - So then you got the glomerulus added, and these glomerulus will very likely
  • fast_forward00:22:59 - be added close to the one that it was split off from.
  • fast_forward00:23:04 - And in this way, I see that these clusters have formed.
  • fast_forward00:23:07 - I don't see that they really, they might not really form a functionally important cluster.
  • fast_forward00:23:17 - Functionally important character, but I find that it's evolutionarily interesting,
  • fast_forward00:23:23 - because these clusters have been built maybe from some proto-glomerulus that they all stem from.
  • fast_forward00:23:32 - So there has been a few bad ones,
  • fast_forward00:23:34 - a few good ones, but then these have evolved and become more and more,
  • fast_forward00:23:38 - If the way it's derived now sounds a bit like I can keep on adding glomeruli
  • fast_forward00:23:42 - until my skull is filled up or my exoskeleton explodes because I have no more
  • fast_forward00:23:48 - space if I look at the mouse the mouse has 1200,
  • fast_forward00:23:52 - but they are much much smaller so you can I think you can keep on adding glomeruli
  • fast_forward00:23:58 - but I think there is also an end to when you need more,
  • fast_forward00:24:04 - that was the whole issue of the effective stimulus space but then in Drosophila
  • fast_forward00:24:09 - to what extent is this really genetically predefined or to what extent and isn't
  • fast_forward00:24:14 - really open to the stimuli the animal is exposed to.
  • fast_forward00:24:19 - What is predefined? The number of glomeruli that they will express.
  • fast_forward00:24:24 - I think it is definitely predefined in the drosophila that we work on today.
  • fast_forward00:24:30 - I mean, we can go from individual to individual to individual, and it will be constant.
  • fast_forward00:24:37 - And we know that glomerulus D, it's always there.
  • fast_forward00:24:41 - We can find it. right so so that
  • fast_forward00:24:44 - that one is is pretty fine but then i'm also sure that
  • fast_forward00:24:48 - there can be during evolution a mutation that is
  • fast_forward00:24:51 - advantageous enough to be become fixed in
  • fast_forward00:24:54 - the population that creates a new a new receptor but
  • fast_forward00:24:57 - then we also know that receptors can pseudogenize and they
  • fast_forward00:25:01 - become inactive so so i'm i mean the
  • fast_forward00:25:04 - over evolutionary over evolutionary time the
  • fast_forward00:25:07 - the system can change it can go backwards it
  • fast_forward00:25:10 - can go forwards it can go left or right so
  • fast_forward00:25:14 - so i'm sure i'm sure that things are happening there but
  • fast_forward00:25:17 - but they take a little too long for us to observe them right what we can do
  • fast_forward00:25:21 - is to go and compare species and that's what we're doing so we can for instance
  • fast_forward00:25:26 - look at all the 12 species of the melanogaster group and and see okay did we
  • fast_forward00:25:33 - have for instance looked at what does diet change mean?
  • fast_forward00:25:37 - So we have one species that have started eating only one single fruit out on the Seychelles.
  • fast_forward00:25:43 - And this fruit smells very, very strongly of a pineapple odor,
  • fast_forward00:25:46 - ethyl hexanoate, and of acids.
  • fast_forward00:25:49 - And the acids make the other species more or less die when they eat it.
  • fast_forward00:25:53 - And here we find a very, very strong effect on the olfactory system of the fly.
  • fast_forward00:25:59 - So this fly has more or less sacrificed three or four other cells that are active in detecting the.
  • fast_forward00:26:12 - The sort of normal drosophila melanogaster odors and
  • fast_forward00:26:16 - instead into those and see like it has put cells that only
  • fast_forward00:26:19 - detect this new type of fruit so so
  • fast_forward00:26:23 - it has zoomed in it has totally zoomed
  • fast_forward00:26:27 - in its its peripheral system towards this
  • fast_forward00:26:30 - fruit and at the same time it has increased the
  • fast_forward00:26:33 - center of the brain the glomeruli that takes care
  • fast_forward00:26:37 - of this input by 200 percent so so
  • fast_forward00:26:41 - it's it's really the first example we know this from
  • fast_forward00:26:43 - sex detection in moths that the
  • fast_forward00:26:46 - male has increased the number of detecting units enormously
  • fast_forward00:26:49 - and at the same time expanded his brain area taking care of female input enormously
  • fast_forward00:26:55 - but this was the first time we see such a thing happening with when it comes
  • fast_forward00:26:59 - to food and diet but then is it is it really the case that for these insects
  • fast_forward00:27:05 - just allocating more real
  • fast_forward00:27:07 - estate to the processing of the signal increases their discrimination ability?
  • fast_forward00:27:12 - Is that all it takes? I would say that it increases their detection ability.
  • fast_forward00:27:17 - Because these flies, they're a bit weak, and they have one competitor.
  • fast_forward00:27:22 - And if they are not there first, they will be out-competed by the other guy.
  • fast_forward00:27:26 - So they're very dependent on detecting the fruit at an early stage of ripeness.
  • fast_forward00:27:32 - At least that what i told you of the of this
  • fast_forward00:27:35 - amplification by numbers is not the only thing because
  • fast_forward00:27:38 - they have also boosted the sensitivity of each neuron
  • fast_forward00:27:41 - by about a thousand times so so they have they have maybe 200 more neurons and
  • fast_forward00:27:50 - then each neuron is a thousand times more sensitive so we get down to a detection
  • fast_forward00:27:54 - limit that very very clearly competes with moth pheromone detection,
  • fast_forward00:28:00 - which is among the most sensitive we know before.
  • fast_forward00:28:02 - So we're down to picogram, nanogram of compound being detected.
  • fast_forward00:28:08 - In terms of these detection thresholds, what's the sensitivity for drosophila
  • fast_forward00:28:15 - at the periphery for these kinds of stimuli?
  • fast_forward00:28:18 - And is that sensitivity also boosted by the processing that happens in these
  • fast_forward00:28:23 - glomeruli in some way? Or you don't know?
  • fast_forward00:28:29 - What we know is that we go down to levels of moth pheromone communication,
  • fast_forward00:28:34 - where we can be playing with 10 molecules, which is really homeopathic concentrations.
  • fast_forward00:28:41 - Then what we have observed in our investigations before is that we sometimes
  • fast_forward00:28:48 - see a boost in amplification at the next level.
  • fast_forward00:28:53 - And this boost we still cannot explain. And we see sometimes a similar thing in Drosophila.
  • fast_forward00:28:59 - So there is something going on after the receptor neuron has detected with its sensitivity.
  • fast_forward00:29:06 - And then to the output levels of the antenna load, we see an augmentation of
  • fast_forward00:29:12 - sensitivity that we still cannot really explain.
  • fast_forward00:29:15 - Okay. So if we talk about things that cannot be explained, so would you claim
  • fast_forward00:29:18 - that to a large extent you understand the system now?
  • fast_forward00:29:21 - Could you really make that claim?
  • fast_forward00:29:24 - Oh, no. Okay. Okay, so where are we with respect to our understanding of this system?
  • fast_forward00:29:29 - Despite the very big investigations, both from our lab,
  • fast_forward00:29:34 - but even more from other labs that have come out lately on these local interneurons,
  • fast_forward00:29:38 - we still don't understand what they do that shuffle the message between glomeruli. Secondly...
  • fast_forward00:29:46 - We lack one very basic thing, and that is how things are hooked up.
  • fast_forward00:29:52 - And that's why we're now entering into very, very detailed electron microscopic
  • fast_forward00:29:56 - investigations of single neurons,
  • fast_forward00:29:59 - of single glomeruli, and trying to understand how are really receptor neurons
  • fast_forward00:30:05 - hooked up to local neurons,
  • fast_forward00:30:07 - how are hooked up to projection neurons.
  • fast_forward00:30:09 - Are there things feeding back in the system?
  • fast_forward00:30:14 - Why do you need to know this? Well, you can never understand the system unless you know how it's wired.
  • fast_forward00:30:22 - We don't even know the basics. No one has ever taken the trouble of looking
  • fast_forward00:30:27 - at the very, very basics.
  • fast_forward00:30:28 - There's one study of cockroaches 10 years, 15 years ago, where Dagmar Malun
  • fast_forward00:30:34 - in Jürgen Birch's lab actually took the trouble of looking at some of the connectivity
  • fast_forward00:30:39 - of the antenna load. Okay.
  • fast_forward00:30:42 - But, I mean, you have neurons that are coming in, and you don't even know what they hook up to.
  • fast_forward00:30:47 - We hypothesize that they might hook up to this neuron or they might hook up
  • fast_forward00:30:52 - to that neuron, but we still don't know.
  • fast_forward00:30:55 - Yeah, but look, on the other hand, you do have a lot of electrophysiology of this system.
  • fast_forward00:30:59 - You know what these projection neurons that are reading out the glomeruli,
  • fast_forward00:31:03 - how they are responding to different kinds of stimuli.
  • fast_forward00:31:05 - Yeah, but why do they respond like that? No, but you also know the dynamics of the glomeruli.
  • fast_forward00:31:09 - So that means apparently something is missing from the pure physiological perspective.
  • fast_forward00:31:15 - So what is missing there?
  • fast_forward00:31:16 - And what's the ambiguity exactly you're trying to resolve now?
  • fast_forward00:31:19 - But there are still different schools.
  • fast_forward00:31:21 - There is the Nobel Prize winner, Richard Axel School, who say that nothing is happening.
  • fast_forward00:31:27 - Things are coming in and things are going out. And it's the same.
  • fast_forward00:31:32 - And then there is the more Gilles Laurent school that says that things are coming
  • fast_forward00:31:38 - in, then they are modified, and then they go out.
  • fast_forward00:31:42 - And here, in this case, I more agree with the Laurent school.
  • fast_forward00:31:46 - I think more and more are doing that.
  • fast_forward00:31:49 - Of course, things are happening in the antenna lobe. It's not just a relay station.
  • fast_forward00:31:53 - Why would we have hundreds and sometimes thousands of local neurons shuffling the message,
  • fast_forward00:32:00 - if you wouldn't need a modification in there
  • fast_forward00:32:02 - well you could have as i say a simple interpretation i will
  • fast_forward00:32:05 - need some gain control because concentrations can vary and
  • fast_forward00:32:09 - i should sort of regulate now the amplitude of my responses and that's it but
  • fast_forward00:32:13 - that's nothing to do with encoding this olfactory space itself of course you
  • fast_forward00:32:19 - could have but we don't see that that's not what we observe as i told you we
  • fast_forward00:32:23 - We see sharpening of images.
  • fast_forward00:32:26 - We see what we think is contrast enhancement, where one odor can more or less
  • fast_forward00:32:32 - turn off all the other glomeruli.
  • fast_forward00:32:35 - It increases the response in one glomerulus enormously, and it depresses the
  • fast_forward00:32:40 - response in all other glomeruli in the whole antenna lobe.
  • fast_forward00:32:44 - Okay. So there are definitely things similar to the visual system going on in there.
  • fast_forward00:32:49 - All right. So in terms of how we encode this olfactory world.
  • fast_forward00:32:58 - Are you also there looking more at, let's say, the Laurent interpretation,
  • fast_forward00:33:02 - like we have some kind of possible temporal coding coming out of the system?
  • fast_forward00:33:06 - Or do you think you see a more spatial kind of coding or rate kind of coding?
  • fast_forward00:33:11 - So where are you going there?
  • fast_forward00:33:13 - Because in the end, of course, for the rest of the brain, what matters is not
  • fast_forward00:33:17 - what the glomeruli do, it's what the projection errors are telling the rest of the system, right?
  • fast_forward00:33:21 - I think we have to look in both ways all the time.
  • fast_forward00:33:25 - I definitely think there is a spatial code of some kind, but what that really
  • fast_forward00:33:32 - means in the readout, I mean, what really means something is which projection
  • fast_forward00:33:37 - neuron will get activated.
  • fast_forward00:33:38 - It and and i mean is this
  • fast_forward00:33:41 - is the spatial code just a product of
  • fast_forward00:33:45 - of that we we have glomeruli in there and it's parcel
  • fast_forward00:33:48 - in this way so that what what we
  • fast_forward00:33:51 - what we choose to see as as a spatial map is is a product of of the connectivity
  • fast_forward00:33:57 - of the antenna lobe i i don't think that's so important i think the main thing
  • fast_forward00:34:01 - is that certain receptor neurons come into one location and the message of those
  • fast_forward00:34:06 - receptor neurons are mainly picked up by projection neurons at the same location.
  • fast_forward00:34:12 - So in that way, you could say that you have some kind of spatial map.
  • fast_forward00:34:15 - But then at the same time, I think it's really important to not forget the temporal
  • fast_forward00:34:20 - aspects, but you also have to choose the way that you look at it.
  • fast_forward00:34:24 - I get very confused by some of the studies that have been done,
  • fast_forward00:34:28 - and I still struggle to understand them really.
  • fast_forward00:34:31 - For what reason? I mean, what's the confusing bit?
  • fast_forward00:34:36 - Took,
  • fast_forward00:34:39 - I mean, you get very, very intricate analysis going on of the oscillations going
  • fast_forward00:34:47 - on, for instance, in the antenna lobe and the mushroom body and so on.
  • fast_forward00:34:52 - And I'm still not, I still haven't got my brain all ready with that.
  • fast_forward00:34:58 - Right. It also has been fairly, it's not that this is all clear cut,
  • fast_forward00:35:02 - right? There's still quite some debate.
  • fast_forward00:35:03 - Oh, there's a lot of debate. This is the right way to look at it, yeah. Yeah.
  • fast_forward00:35:07 - But I also have this feeling that we have more to learn about,
  • fast_forward00:35:11 - for instance, coincidence detection.
  • fast_forward00:35:14 - I think that is one way that you could augment the sensitivity of the system
  • fast_forward00:35:18 - in the way that we don't understand right now, so that we see the higher sensitivity
  • fast_forward00:35:22 - at the second level that we could explain by theory from just a mere convergence.
  • fast_forward00:35:29 - And this higher increase could be explained by, for instance,
  • fast_forward00:35:35 - cells going into synchrony on
  • fast_forward00:35:38 - the antenna, and then this synchrony being detected in the antenna lobe.
  • fast_forward00:35:42 - And that's exactly what we're trying to get at now by doing multiple recordings
  • fast_forward00:35:46 - from neurons on the antenna. So have you seen this kind of synchrony?
  • fast_forward00:35:50 - The analysis, we did it a few months back.
  • fast_forward00:35:54 - But the analysis to get at, to get really, to get, okay, here the stimulus reaches
  • fast_forward00:36:00 - both of these neurons exactly at this millisecond, and then go into the analysis
  • fast_forward00:36:05 - and say that, okay, after 10 milliseconds, they start spiking together.
  • fast_forward00:36:09 - Right. That takes some time. Okay. So now, we'll talk about the evolution here,
  • fast_forward00:36:15 - right, certainly in this meeting.
  • fast_forward00:36:17 - And it was sort of interesting, maybe also ironic, that you said,
  • fast_forward00:36:21 - well, olfaction is a bit like a visual system. But from an evolutionary perspective,
  • fast_forward00:36:25 - you could also make the argument that actually the visual system is like the olfactory system.
  • fast_forward00:36:29 - And so where do you stand on that issue?
  • fast_forward00:36:32 - Do you see really that the olfactory system is like a proto-sensory system?
  • fast_forward00:36:39 - Whose principles have been generalized towards other modalities,
  • fast_forward00:36:43 - or what's your take on that?
  • fast_forward00:36:46 - I think all these sensory systems are created from cilia.
  • fast_forward00:36:51 - And cilia were there from the beginning. We have cilia in different forms on all organisms.
  • fast_forward00:36:58 - And as Heather Eisen was saying in her talk here at the conference,
  • fast_forward00:37:01 - for instance, probably chemoreception and mechanoreception were the two first sensory systems.
  • fast_forward00:37:11 - And if we then compare, probably the cilia of the visual system might have occurred
  • fast_forward00:37:19 - from the mechanosensories and cilia in some way.
  • fast_forward00:37:22 - And you have got the rhodopsin integrated and so on.
  • fast_forward00:37:26 - So I think it's very hard to talk about the proto-sense of some way.
  • fast_forward00:37:33 - I find the old theory... That is interesting because you're sidestepping the
  • fast_forward00:37:38 - issue a bit by focusing so much at the sensory periphery, right?
  • fast_forward00:37:41 - You could still argue that the processing that has been performed,
  • fast_forward00:37:46 - is being performed by the antenna lobe, combined with their projection neurons,
  • fast_forward00:37:51 - and maybe a little bit downstream from that, that provides, let's say,
  • fast_forward00:37:55 - the proto-processing principles of any sensory modality,
  • fast_forward00:38:00 - irrespective of how the periphery gets you the specific signals.
  • fast_forward00:38:04 - Would you buy that? Also that you would not buy necessarily.
  • fast_forward00:38:08 - I mean, you can compare it. If you look at audition hearing,
  • fast_forward00:38:13 - then you have this, that you have certain frequencies being taken care of in
  • fast_forward00:38:18 - certain barrels in our auditory cortex and so on.
  • fast_forward00:38:21 - So I think that this parcellation definitely occurs in different sensory systems. On the other hand,
  • fast_forward00:38:29 - The glomerulus formation we see all over the place.
  • fast_forward00:38:35 - We see some organisms that have an agglomerular input from receptor neurons,
  • fast_forward00:38:41 - but I see them as the exception.
  • fast_forward00:38:43 - I don't agree with some of what we heard earlier here at the conference,
  • fast_forward00:38:47 - that there are many, many.
  • fast_forward00:38:49 - I think there are a few where we don't see this.
  • fast_forward00:38:53 - But take an antenna and move it to the place of a leg of a fly,
  • fast_forward00:38:57 - and glomeruli will be formed where the nerves hit the nervous system.
  • fast_forward00:39:03 - So I mean, olfactory receptor neurons have the capability of forming glomeruli
  • fast_forward00:39:08 - where they hit the olfactory system in more or less any organism.
  • fast_forward00:39:12 - So this seems to be a general principle that has evolved probably independently
  • fast_forward00:39:17 - in several different lineages during evolutionary time.
  • fast_forward00:39:22 - So I think that is a very basic way of organizing chemo detection.
  • fast_forward00:39:29 - But then if you look at how visual, then you don't see this kind of architecture.
  • fast_forward00:39:35 - Well, but still you would have some patterns of convergence and divergence that
  • fast_forward00:39:40 - are especially convergence initially that are regulated in some form.
  • fast_forward00:39:45 - So you might speculate to say, well, the formation of the glomerulus is like
  • fast_forward00:39:52 - your proto-receptive field.
  • fast_forward00:39:54 - And other sensory modalities that's thrown in, let's say, a thalamus,
  • fast_forward00:39:58 - an intermediate processing stage, just developed a more complicated form of a glomerulus.
  • fast_forward00:40:03 - But now it really became a mechanism to define more complex receptive fields.
  • fast_forward00:40:09 - I mean, I'm just sucking this out of my thumb right now, but you could tell
  • fast_forward00:40:13 - a story along these lines that you could try to defend.
  • fast_forward00:40:15 - But that's not necessarily one you would buy right now. You would really see
  • fast_forward00:40:20 - it as separate principles for separate modalities.
  • fast_forward00:40:24 - Yes, basically. But at the same time, I agree that you can definitely have receptive
  • fast_forward00:40:30 - fields and that it gets organized, of course.
  • fast_forward00:40:33 - Organization is needed for sensory detection.
  • fast_forward00:40:36 - Right. But I don't see direct parallels when I look at the olfactory system
  • fast_forward00:40:40 - and the visual system, for instance.
  • fast_forward00:40:43 - So I think more and more science is needed.
  • fast_forward00:40:47 - But before we can say that, there has been a lot of evolution going on since they were born.
  • fast_forward00:40:53 - Yeah that that's what you guys tell me so now
  • fast_forward00:40:57 - um so another thing you're
  • fast_forward00:41:00 - doing here on the island is to look at specific species of crabs or specific
  • fast_forward00:41:04 - particular one the rubber crab right so so why is that really how is this helping
  • fast_forward00:41:09 - us to understand your factory system well here we are really interested in understanding
  • fast_forward00:41:14 - how does the sensory system adapt during evolutionary time
  • fast_forward00:41:18 - to go from detection in water to detection in air and this has happened during
  • fast_forward00:41:24 - the last five million years it's a pretty fast process and we know also interesting
  • fast_forward00:41:29 - new facts about different kinds of
  • fast_forward00:41:31 - receptors detecting different kinds of stimuli we know that this the old.
  • fast_forward00:41:38 - Evolutionarily, probably old ionopropyl receptors are very active in detecting
  • fast_forward00:41:43 - waterborne compounds and so on.
  • fast_forward00:41:45 - So what we're trying to look at is basically all the way from the antenna into
  • fast_forward00:41:50 - the brain, what has happened to these guys.
  • fast_forward00:41:53 - And it's not only in this species, but then we're comparing to other species.
  • fast_forward00:41:57 - And what we find really interesting is that different species of crustaceans
  • fast_forward00:42:02 - have taken totally different evolutionary pathways.
  • fast_forward00:42:05 - Pathways so out of the five lineages that went down to land we have chosen mainly
  • fast_forward00:42:11 - two to look at and that's the the hermit crabs and the isopods the woodlice and they have taken,
  • fast_forward00:42:19 - diametrically different pathways so the the
  • fast_forward00:42:22 - hermit crabs they have expanded the brain area that take care of olfactory input
  • fast_forward00:42:27 - to occupy almost 50 percent of their brain while isopods have totally decreased
  • fast_forward00:42:35 - almost to zero the part of their brain that takes care of olfactory input.
  • fast_forward00:42:41 - So I find this very interesting. Why do two different types of the same type
  • fast_forward00:42:48 - of animal, crustacean basically, when they go on to land.
  • fast_forward00:42:53 - Go in so diametrically different evolutionary directions?
  • fast_forward00:42:57 - And that's what we're trying to understand. To understand it, we do,
  • fast_forward00:43:01 - do we have we are studying the antenna we're studying all the receptors set
  • fast_forward00:43:06 - up so far we have only found gustatory receptors and ionotropic receptors we
  • fast_forward00:43:11 - cannot find our type of olfactory or the insect type right and at the same time
  • fast_forward00:43:18 - we're doing the brain anatomy we're looking at
  • fast_forward00:43:21 - how it's built how things project how the different centers are constructed
  • fast_forward00:43:26 - comparing comparing between isopods and crustaceans and the hermits and so on.
  • fast_forward00:43:33 - We were in the middle of that project, but evolutionarily I find it extremely
  • fast_forward00:43:37 - interesting because we have sort of an experiment that has been going on during
  • fast_forward00:43:43 - the last five million years.
  • fast_forward00:43:44 - Right. But now it seems a bit counterintuitive, right? Because aren't you sort
  • fast_forward00:43:49 - of swimming against the current now?
  • fast_forward00:43:52 - Because, you know, we have preparations like Drosophila, like the mouse,
  • fast_forward00:43:56 - which are in some sense becoming now the standard preparation because we know so much about them.
  • fast_forward00:44:02 - And what we have is molecular access to them that they can become highly controlled
  • fast_forward00:44:07 - experimental preparations.
  • fast_forward00:44:08 - And now you come and you find some really very odd crab species to start to
  • fast_forward00:44:14 - look at, about which we know very little.
  • fast_forward00:44:16 - So isn't it a high-risk operation?
  • fast_forward00:44:19 - Of course, but at the same time, I think it's highly dangerous to get stuck
  • fast_forward00:44:23 - only in the model species.
  • fast_forward00:44:25 - So we should use the model species to the utmost, and I really like working
  • fast_forward00:44:30 - on Drosophila, But at the same time, of course, we need a comparison with other systems.
  • fast_forward00:44:35 - Otherwise, we get extremely narrow in our view of the world.
  • fast_forward00:44:41 - And we get totally Drosophila-centric or Musa-centric or whatever you would say.
  • fast_forward00:44:46 - And I mean, we need comparison. And to understand evolution specifically,
  • fast_forward00:44:51 - you can never understand evolution only by looking at Drosophila melanogaster,
  • fast_forward00:44:54 - an animal that has been totally associated with humans during the last 15,000 or 25,000 years.
  • fast_forward00:45:02 - So it's really, really needy that we also keep our eyes open,
  • fast_forward00:45:07 - and that's what I really like to do.
  • fast_forward00:45:09 - I like to use the model system, but I also really like to go outside of that
  • fast_forward00:45:15 - and to try to understand what has really gone on in nature.
  • fast_forward00:45:20 - Right. So then how many years will it take for us to understand this crab now?
  • fast_forward00:45:25 - Oh they you know when you start that
  • fast_forward00:45:28 - on a new system like this one first you have
  • fast_forward00:45:31 - to nail down the the ecology of the
  • fast_forward00:45:34 - species to try to understand what they are doing and what
  • fast_forward00:45:37 - you should basically do is just to sit down in your ass for one year and watch
  • fast_forward00:45:41 - the crab but we don't have time to do that most of us so are you good in this
  • fast_forward00:45:46 - we i now have one postdoc on the island and she's doing massive marking of the
  • fast_forward00:45:52 - crabs and we're really trying to get the impression of what's going on.
  • fast_forward00:45:56 - And we're marking them with GPS loggers and so on to try to understand their
  • fast_forward00:46:01 - movements and basically how they interact.
  • fast_forward00:46:04 - But all of this is supposed to form the base for...

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