ECR Spotlight – Corinna Gebehart

Corinna Gebehart

Describe your scientific journey and your current research focus

In 2018, I started my PhD in the lab of Ansgar Büschges at the University of Cologne, Germany, where I studied how proprioceptive signals are integrated in the nerve cord of the stick insect. I took recordings from nonspiking neurons using sharp electrodes and fully fell for the highs and lows of electrophysiology. After defending my PhD in 2021, I started a postdoc in the lab of Eugenia Chiappe at the Champalimaud Foundation in Lisbon, Portugal. Here, I moved from sharp electrodes and nonspiking neurons to patch clamp and spikes, and from stick insects to Drosophila. The lab had previously shown that non-visual walking-related signals can be found even in visual circuits, and my project focuses on the (proprioceptive) signals that the fly's nerve cord provides to the brain during locomotion, and how these signals are integrated.

How would you explain the main message of your Review to a member of the public, and how would you explain the broader impact of research in this area?

Proprioception, the sense of a body's own movements, consists of a multitude of individual senses, such as movement, force, or position, and is conserved across animal species, from humans to fruit flies. A large part of the processing of these signals happens in the nerve cord and does not rely on the brain, yet we still do not fully understand how the neuronal circuits in the nerve cords of animals process this barrage of signals, and how they allow for both robustness and flexibility. Since the tasks and challenges of proprioception apply to many animals at different scales, and given their smaller neuron numbers and experimental accessibility, research in this area often makes use of insect model systems. In this Review, we summarize and discuss the current state of knowledge on these circuits in insect model systems, their architecture and function. We discuss how these circuits can integrate signals from different proprioceptive senses, and how they balance robust, fast responses (for example to quickly escape a predator), with the flexibility required to move through complex environments.

Is there anything that you learned while writing this Review that surprised you?

It should not have come as a surprise, but the complexity of these circuits in what are often termed ‘simple’ organisms always astonishes me. Unlike vertebrate nervous systems that operate with neurons in the thousands and millions, flies and insects must make do with much smaller networks that often barely reach the hundreds. And yet, when running around, encountering obstacles, balancing their own body, and navigating the world, insects often are just as, if not more, dexterous than many vertebrates. And despite their smaller, more ‘manageable’ one could say, circuits, we still do not fully understand how they do it.

What was your approach in organising background material and shaping this Review?

We discussed very early on what should be the main topics of the Review, mostly by collecting topics and questions that had come up again and again in our own discussions in the lab or in other people's work – basically, the questions and focus we would have liked to read a review about. And then we started shaping the sections and filling in the gaps with either the studies we found that answered some of our questions – or the questions that are still open in the field. Because we had discussed many of these points over the years in the lab, during meetings, or over coffee breaks, the writing process felt very organic; and the sending of the manuscript back and forth between Ansgar and me, especially in the early stages, felt almost like a continuation of these discussions.

What do you see as the main value of Review-type articles?

Reviews are a great way of condensing and discussing a set of ideas that are bouncing around a research community and backing them up with literature. Personally, I do not even have to necessarily agree with every aspect of the authors' perspective, just seeing a different side or reading about new aspects helps me clarify my own stance on the matter.

Are there any important historical papers from your field that have been published in JEB? If so, which papers, and how did they pave the way for later research?

Actually a lot of the historical background that the field of (insect) proprioception builds its current ideas on was originally published in JEB, for example the connection between position-sensitive afferents and motor neurons in the cockroach leg by Pearson et al. (1976; ‘Connexions between hair-plate afferents and motoneurones in the cockroach leg’; doi:10.1242/jeb.64.1.251), the role of movement afferents for walking movements in stick insects by Bässler (1988; ‘Functional principles of pattern generation for walking movements of stick insect forelegs: the role of the femoral chordotonal organ afferences’; doi:10.1242/jeb.136.1.125), the signal processing along local reflex pathways by Burrows (1989; ‘Processing of mechanosensory signals in local reflex pathways of the locust; doi:10.1242/jeb.146.1.209), or the original description of nonspiking interneurons controlling a joint of the stick insect leg by one of the authors in this study (Büschges, 1990; ‘Nonspiking pathways in a joint-control loop of the stick insect Carausius morosus’; doi:10.1242/jeb.151.1.133).

If you had unlimited funding, what question in your research field would you most like to address?

How the proprioceptive sense arises within the central nervous system – not how individual proprioceptive modalities from individual sense organs are processed, but how the whole concerted action of a huge number of sensors in different positions with different sensitivities leads to the nervous system knowing where it is, where it is going, and what it needs to do next to not fall onto its face.