Multiple time scales in simple habituation.

Habituation is the waning of a reflex response to repeated stimulation. Habituation to closely spaced stimuli is faster and more complete than to widely spaced stimuli, but recovery is also more rapid (rate sensitivity). We show that a 2-unit, cascaded-integrator dynamic model can explain in detail an extensive data set on rate-sensitive habituation in the nematode Caenorhabditis elegans. Many apparently complex properties of habituation and learning dynamics may reflect interactions among a small number of processes with different time scales.