The computational worm: spatial orientation and its neuronal basis in C. elegans

Spatial orientation behaviors in animals are fundamental for survival but poorly understood at the neuronal level. The nematode Caenorhabditis elegans orients to a wide range of stimuli and has a numerically small and well-described nervous system making it advantageous for investigating the mechanisms of spatial orientation. Recent work by the C. elegans research community has identified essential computational elements of the neural circuits underlying two orientation strategies that operate in five different sensory modalities. Analysis of these circuits reveals novel motifs including simple circuits for computing temporal derivatives of sensory input and for integrating sensory input with behavioral state to generate adaptive behavior. These motifs constitute hypotheses concerning the identity and functionality of circuits controlling spatial orientation in higher organisms.

► C. elegans exhibits two forms of spatial orientation behavior, klinokinesis and klinotaxis, both of which require computation of the time derivative of chemosensory information. ► The time derivative is computed partly at the cellular and partly at the network level. ► The output of chemosensory neurons modulates the probability of stochastic course-correction events in klinokinesis ► It is hypothesized that course corrections in klinotaxis require phasic sensory gating at the level of motor neurons.