The emergence of stereotyped behaviors in C. elegans

TL;DR

This paper presents a stochastic model explaining how stereotyped crawling behaviors and reversals in C. elegans emerge from the dynamics of its entire body shape, without relying on discrete command neurons.

Contribution

It introduces a simple, parameter-free model that reproduces the reversal rate and stereotyped trajectories observed in C. elegans crawling behavior.

Findings

Model accurately predicts reversal rates within experimental error

Reproduces stereotyped trajectories near reversals

Demonstrates emergence of behavior from whole-body dynamics

Abstract

Animal behaviors are sometimes decomposable into discrete, stereotyped elements. In one model, such behaviors are triggered by specific commands; in the extreme case, the discreteness of behavior is traced to the discreteness of action potentials in the individual command neurons. We use the crawling behavior of the nematode C. elegans to explore the opposite extreme, in which discreteness and stereotypy emerges from the dynamics of the entire behavior. A simple stochastic model for the worm's continuously changing body shape during crawling has attractors corresponding to forward and backward motion; noise-driven transitions between these attractors correspond to abrupt reversals. We show that, with no free parameters, this model generates reversals at a rate within error bars of that observed experimentally, and the relatively stereotyped trajectories in the neighborhood of the reversal also are predicted correctly.