Wind direction coding in the cockroach escape response: Winner does not take all

Cockroaches respond to the approach of a predator by turning away and then running. Three bilateral pairs of giant interneurons are involved in determ ining the direction of the sensory stimulus and setting the turn direction. Each of these six interneurons has a different directional response to win d stimuli. We have tested whether these six cells use a winner-take-all mec hanism to perform this directional determination: that is, each of these ce lls suppressing the motor response that each of the other cells promotes. S uch a mechanism is found in similar behaviors of some other animals. By add ing spikes to identified giant interneurons through intracellular stimulati on during the sensory-induced behavior and analyzing the resulting directio nal leg movements, we find that a winner-take-all is not used in this syste m. Rather, directional determination appears to be based on collaborative c alculation of direction by the giant interneurons as a group.