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Join Dennis Eckmeier on an expedition from neuroscience to science communication
Today I invite you to join me on an expedition with Dr. Dennis Eckmeier through the academic jungle to the realms of science communication. You will learn about the courtship calls of Chinese fire-bellied toads, a blowfly flight simulator, the vision of zebra finches (yes, finches, not fish!), and how the memory of smell might already start in the nose. All this comes together with some advice for early career scientists among you. Let the journey begin…
How frogs called Dennis to do neuroscience
Dennis’ scientific interest started – as it might for many – with dinosaurs. But he wasn’t only fascinated by their exotic and mystical appearance, he wanted to dig deeper. “What fascinated me about dinosaurs and others like prehistoric humans was how evolution kind of shaped them and their behavior and their ecology. I feel like very early on I had a feeling for the complexity of life,” he answers to my question what ignited his interest in science and led him to study biology.
Dennis is originally from Germany and completed his undergraduate degree at the University of Cologne, where he also got his first research position in a lab focused on neurophysiology. That’s where he got in touch with Chinese fire-bellied toads and studied their courtship calls. Male toads have a very stereotypical courtship call which is just one tone that is repeated at a certain rate. Researchers figured out that when there are lots of males in a pond during mating season, they try not to call simultaneously. “When another one calls and their rates are colliding, one of them would stop. Wait a certain amount of time and then restart,” Dennis explains.
His task was to recreate this phenomenon in the lab. For this purpose, he put a toad in an aquarium, and because it is a very simple call, he was able to recreate it with a synthesizer – in 2005 that was a pretty cool thing to do. It was known that the pitch of the call and the rate depended on the size of the frog and the water temperature. So, Dennis simulated different frog sizes in different water temperatures and tried to figure out if the real frog would be more forceful when the sound of the frog’s call colliding with his own was supposedly smaller than he was. But it was always the real frog that stopped calling. While these results were interesting, they weren’t a big breakthrough.
However, this was also the time when he first did hands-on electrophysiology experiments. Neurons communicate with each other using electric signals. With this technique – sticking tiny electrodes into certain areas of the frogs’ brains and measuring differences in the electric signals – Dennis tried to figure out which areas were activated when the frogs were calling. They stimulated the auditory nerve that usually receives acoustic signals from the call and recorded what happened in the nerves that control the glottis and breathing. “So, I could see whether the stimulation in a certain pattern would evoke what we call a ‘virtual’ calling in these frogs.” Through these experiments, he was able to reproduce how the brain produces these calls and how it reacts to certain calling patterns, which was a big accomplishment for him as an undergrad researcher.
Frogs cannot fly, but blowflies and zebra finches can
Dennis was hooked and wanted to continue with neuroscience research, but since the University of Cologne didn’t have a PhD position to offer, he moved to Bielefeld University. In his new laboratory, he was exploring the vision of zebra finches. When I heard that the first time, I was curious. Zebrafish are a common model organism for biology research, but a zebra finch? Not so much. Dennis clarified that zebra finches are mostly famous for research in vocalization, but his lab was more interested in how these animals gather 3D visual information from their environment. At the time, Dennis was part of a collaborative project with a lab that worked on another organism, blowflies, specifically studying how blowflies see their 3D environment while they are flying.
Humans see objects in 3D because both our eyes record a slightly different version of the field of vision before us, which is then put together by our brain. To do this correctly, how far apart our eyes are really matters (Figure 1). The eyes of flies, however, are too close together to create this type of stereo image. So, they rely on other mechanisms to visualize the world around them in 3D. The researchers hypothesized that they reconstruct the 3D world from the visual flow on their retina by comparing the current image with the past one. That might be easy when the fly flies in a straight line, but what happens when it turns into a curve? Through a very tedious method where the researchers recorded the flight of a single fly with several cameras, they reconstructed the fly’s flight trajectory in space which made them realize that flies do not fly curves, but turn rather quickly – like a zigzag.
Now comes the cool part. From the fly’s flight pattern, the researchers built a “fly – flight – simulator,” which was a movie from the fly’s perspective projected on a panoramic 3D screen with LEDs. In 2008, when this was developed, it was a pretty advanced technology. Then, another fly was put into this apparatus and immobilized. This gave the researchers the possibility to record the fly’s brain activity with electrophysiology while it was experiencing its virtual flight. “They figured out that some neurons were more engaged when the fly was going straight, rather than turning. The neurophysiological measurement correlated to what they expected that would happen,” he adds.
In his own experiments, he was trying to do the same thing with zebra finches. Their eyes are also close together, so it’s unlikely that they have stereo vision as we do. “So, what we did was an experiment, where we forced the birds to fly a curve,” Dennis explains and adds with a smirk, “Well, forced sounds too harsh – we convinced them to do it.” He recorded them from above and from the side while the bird was flying around an obstacle (Figure 2).
“They move their head in a way to avoid rotational flow in their eyes – the same effect as with the flies when they zig and zag. Their body makes a smooth curve, but they use their head movement to compensate for the rotational part of it,” Dennis tells me. That was a good indication that these birds have the same processing of the optical flow as blowflies do [1]. However, the electrophysiological measurements turned out to be much more complicated in birds than in flies and did not result in a clear picture, but gave an exploratory, early look at what happens during a bird’s fly [2].
A move across the ocean to explore the sense of smell
After his PhD, Dennis continued doing neuroscience research in the Cold Spring Harbor Laboratory on Long Island. “I’m a pretty self-confident person and don’t shy away from big projects and I was certain to be a professor at some point, so I thought I have to move on and do a postdoc,” he tells me. That started an intense time in his life, because of a demanding project and the expense of living on Long Island. Research-wise, he was working now with yet another research animal – the mouse. Many experimental methods for research have been established in mice, like imaging techniques to visualize certain neurons in the brain. “I moved to mice to learn those methods there and in the meantime, they (other researchers) can catch up with the birds and I can go back to birds and can do cool stuff with birds again,” he explains and adds with a smile, “That didn’t work out, but at least that was my strategy.” The focus of this lab was social interaction. Research shows that mammals use smell for social identification. There are many social cues in the smell of another mouse, mostly in urine. The question was how neurons change in the so-called main olfactory bulb – one brain area that processes odors – in response to a smell when something exciting is going on.
His advisor previously found that when you stimulate the release of norepinephrine (NE), a neurotransmitter that prepares the body for action, in an anesthetized mouse and you present that mouse with a smell, you get a very specific response in neurons in the main olfactory bulb. Even though the mouse was unconcious, it later remembered that smell that was presented to it, something that was dependent on the administration of NE. Dennis added to this knowledge that smell and norepinephrine did not only evoke this neuronal reaction in the brain, but also in the neurons that come from the nose. “The first cells that detect the smell are somehow involved in the whole learning process,” Dennis explains. “The way memory works is that you have so many little parts to it that change a slight little bit to create a memory in the brain. () That was the moment that I understood how memory works in the brain and that was pretty cool!”.
“Everything is always in motion” – Back to Europe and the start of a new life chapter
The last station in our expedition with Dennis is Portugal, where he moved after completing his research in the U.S. There, he started to study the locomotion of mice, but soon his path also led more and more into science communication activities, culminating in the organization of the “March for Science” satellite event in Lisbon together with a group of researchers from his research institute. His goal was to fight against ignorance from politicians or the public towards pressing topics like climate change. He is convinced that “We (scientists) need to communicate to the public because we live in a democracy and the people need to be able to judge what politicians are trying to do,” and adds, “Human reasoning is pretty flexible whereas physics isn’t flexible. When we talk about things like climate change, people need to understand that we cannot act on climate change the same way as we act on social problems where there is some wiggle room… () Physics is physics. The world heats that much, then that’s the end of civilization and that’s a given.”
Many scientists underestimate the power of effective communication, but not Dennis. “There are all these principles that you can use and you can really be creative with it and create something that is effective in communicating what you wanted to say and I found that fascinating!,” he smiles. Whenever he was practicing academic communication, he tried to be very good at it, either by giving talks or preparing poster presentations. At the time, his goal was still to become a professor, which in his opinion also requires good communication skills. “You will also not be successful in getting your papers published if you cannot write properly and you won’t be good at interviewing for jobs if you are unable to give a good presentation,” he adds, a passion that he is now trying to convey to young scientists by giving tips for science writing and science communication on Youtube.
After the “March of Science” when most of his colleagues moved back to the bench, he moved one step further into a science communication career and started his own podcast that is geared towards early career scientists, but also contains interesting topics for everyone: Stories about scientists and their role in society, talking about politics, and discussing how to make science (and the academic system) better. Check it out at https://www.scienceforprogress.eu/ (in English; Dennis grew up bilingual German and English)!
Dennis is now back in Germany where his science journey began and if you want to continue following Dennis on his science expedition which not only contains research, but also science editing, podcasting, explanatory videos, and articles, you can find him on social media (handles below) or on his website!
I hope you had as much fun as I had during this expedition from frogs to communication and beyond!
References
[1] Eckmeier D, Geurten BR, Kress D, Mertes M, Kern R, Egelhaaf M, Bischof HJ. Gaze strategy in the free flying zebra finch (Taeniopygia guttata). PLoS One. 2008;3(12):e3956. doi: 10.1371/journal.pone.0003956. Epub 2008 Dec 24. PMID: 19107185
[2] Eckmeier D, Kern R, Egelhaaf M, Bischof HJ. Encoding of naturalistic optic flow by motion sensitive neurons of nucleus rotundus in the zebra finch (Taeniopygia guttata). Front Integr Neurosci. 2013 Sep 20;7:68. doi: 10.3389/fnint.2013.00068. eCollection 2013. PMID: 24065895
[3] Eckmeier D, Shea SD. Noradrenergic plasticity of olfactory sensory neuron inputs to the main olfactory bulb. J Neurosci.2014 Nov 12;34(46):15234-43. doi: 10.1523/JNEUROSCI.0551-14.2014. PMID: 25392492
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