Complex Modal Decomposition Applied to Nematode Posturing

The complex orthogonal decomposition (COD), a process of extracting complex modes from complex ensemble data, is summarized, as is the use of complex modal coordinates. A brief assessment is made on how small levels of noise affect the decomposition. The decomposition is applied to the posturing of a wild Caenorhabditis elegans nematode. The decomposition indicates that the worm has a multi-modal posturing behavior, involving at least a dominant locomotion mode and a secondary, steering mode. The locomotion mode is closer to a pure traveling waveform than the steering mode. The characteristic wavelength of the primary mode was estimated in the complex plane. Frequency was obtained from the complex modal coordinate's complex whirl rate of the complex modal coordinate, and from its fast Fourier transform.