  A quantitative understanding of how sensory signals are transformed into
motor outputs places useful constraints on brain function and helps reveal the
brain's underlying computations. We investigate how the nematode C. elegans
responds to time-varying mechanosensory signals using a high-throughput
optogenetic assay and automated behavior quantification. In the prevailing
picture of the touch circuit, the animal's behavior is determined by which
neurons are stimulated and by the stimulus amplitude. In contrast, we find that
the behavioral response is tuned to temporal properties of mechanosensory
signals, like its integral and derivative, that extend over many seconds.
Mechanosensory signals, even in the same neurons, can be tailored to elicit
different behavioral responses. Moreover, we find that the animal's response
also depends on its behavioral context. Most dramatically, the animal ignores
all tested mechanosensory stimuli during turns. Finally, we present a
linear-nonlinear model that predicts the animal's behavioral response to
stimulus.
