Behavioral and neuronal analyses of the escape response to looming stimuli in the crab Chasmagnathus

OLIVA D., MEDAN V., TOMSIC, D.

Lund, Suecia

Conferencia; International Conference on Invertebrate Vision; 2008

An object that approaches on a collision course (looming stimulus) triggers in Chasmagnathus a strong directional escape response. Recently, we have shown that this response can be reliably elicited and precisely measured in the laboratory using computer generated images. Moreover, by performing in vivo intracellular recordings from the optic lobe, we found two classes of lobula giant (MLG1 and MLG2) projecting neurons that appear to play a key role in the behavioral response to looming stimuli (Oliva et al. 2007). Here we studied the escape response to sets of looming stimuli that varied either in size or speed of approach. Results show that the speed of run goes up with the increasing velocity of the image expansion and decelerate at the end of the  expansion, indicating that the run is continuouslycontrolled by the visual input. We then evaluated the performance of the two classes of LG neurons to the same set of stimuli. Results show that the firing rateincreases proportionally to the velocity of image expansion. Moreover, the firing rate appears to convey enough information to control the acceleration of running.