Analysis of Planar Shapes through Shape Dictionary Learning with an Extension to Splines
Anna Song, EPFL STI LIB

Meeting • 28 August 2018

Abstract
C. Elegans worm is a model organism extensively studied by biologists, easy to observe and manipulate. It is the only animal up to now whose connectome is entirely known. An active research field aims at linking its genetic material to motor behavior: indeed, investigating their swarming or swimming movements is the simplest way to observe some change due to a mutation. In such a context, we propose to analyse their shapes using Kendall's celebrated shape space theory (1977). Using Hermite splines or landmarks to segment worms, we extend his theory to spline curves, especially in the planar case where the complex setting is incredibly clear and simple. This allows us to embed some of the lab's previous work into this more general framework. Our main contribution is to introduce a sparse Shape Dictionary which is able to reconstruct any worm with few atoms. Most importantly, our atoms resemble realistic worms. This leads to interpretable weights, and two complementary ways for visualizing the dynamics of a worm. We hope that this method will be useful in the future for linking movement features to mutations, and for other living organisms as well.