Asymmetric adaptation reveals functional lateralization for graded versus discrete stimuli

Abstract 150 words Animal navigation strategies depend on the nature of the environmental cues used. In the nematode Caenorhabditis elegans , navigation has been studied in the context of gradients of attractive or repellent stimuli as well is in response to acute aversive stimuli. We wanted to better understand how sensory responses to the same stimulus vary between graded and acute stimuli, and how this variation relates to behavioral responses. C. elegans has two salt-sensing neurons, ASEL and ASER, that show opposite responses to stepped changes in stimulus levels, however only ASER has been shown to play a prominent role in salt chemotaxis. We used pre-exposure to natural stimuli to manipulate the responsiveness of these neurons and tested their separate contributions to behavior. Our results suggest ASEL is specialized for responses to acute stimulus changes. We also found that ASER remains responsive to graded stimuli under conditions where it is unresponsive to large steps.