Universität zu Köln

Godesberg, Vincent ORCID: 0000-0002-9903-0220 (2025). Natural variability of walking behavior in Drosophila melanogaster. PhD thesis, Universität zu Köln.

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Abstract

Walking behavior in insects serves as a model for studying motor control, offering insights into general locomotor principles. Although much is known about how the nervous system regulates insect locomotion, variability in walking behavior within and across individuals of the same species has been understudied. This thesis aims to close the gap of knowledge by investigating the natural variability of walking behavior in Drosophila melanogaster. High-speed videography and automated, deep learning-based tracking were used to collect extensive data of leg-tip kinematics in 2D from a large cohort of wildtype flies. Principal component analysis (PCA) was applied to unbiasedly explore patterns of covariance in the data set. Five principal components (PCs) were found to explain the majority of the observed variability. A set of two PCs primarily represented general interleg coordination patterns, the former reflecting the characteristic tripod gait that is widely observed in insect locomotion and the latter reflecting the systematic deviation from canonical tripod coordination. In contrast, the remaining three PCs captured idiosyncrasies in posture and leg movements, which remained stable across different speeds, suggesting that each fly maintains a unique, consistent walking signature. Although displaying the same idiosyncrasies across walking speeds, the relative fraction of variability described by these three PCs decreased for higher speeds, while the PC describing tripod coordination markedly gained significance. This finding indicates, that interindividual variability of leg-tip kinematics decreases with increasing walking speeds, which is further investigated by analyzing the correlation of spatial and temporal variability with walking speed and measures of interleg coordination. For this purpose, tripod coordination strength (TCS) was used as a proxy for interleg coordination and a novel coherence measure was designed to quantify how well timed intersegmental influences between adjacent legs are. I show that the coherence measure in direct comparison outcompetes walking speed and TCS at predicting both spatial and temporal variability. This result suggests that the stronger entrainment of weakly coupled oscillators controlling single leg movements is causally related to the observed decrease in variability as walking speed increases. Finally, I developed an advanced experimental setup to enable continuous high-resolution recordings of freely walking flies over long durations, capturing kinematic data at up to 200 Hz. This setup, combined with optimized data processing tools, enabled a robust collection of leg-tip kinematics and efficient filtering for behavior of interest, which was demonstrated by a rudimentary analysis of curved walking behavior. Overall, this thesis provides a comprehensive quantitative analysis of the natural variability in Drosophila walking behavior. By separating general motor control features from idiosyncrasies and systematically analyzing how key parameters of walking behavior interact with variability, this work offers novel insights into the underlying neural mechanisms enabling consistent and adaptive motor control. The presented findings might serve as a foundation for future studies on how neural circuits generate flexible and yet robust behaviors in both insects and vertebrates.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Godesberg, Vincent vgodesbe@smail.uni-koeln.de orcid.org/0000-0002-9903-0220 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-748694
Date:	6 January 2025
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Biology > Zoologisches Institut
Subjects:	Natural sciences and mathematics Life sciences
Uncontrolled Keywords:	Keywords Language Walking English Drosophila English Variability English
Date of oral exam:	17 December 2024
Referee:	Name Academic Title Büschges, Ansgar Prof. Nawrot, Martin Prof. Höcker, Ute Prof.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/74869