Escape behavior in the cockroach: distributed neural processing.

Escape reactions are often considered to be among the simplest behaviors. The nerve circuits guiding these reactions are also generally thought to be simple. For instance, in several species a single interneuron is sufficient to trigger normal escape. The evasive response of the cockroach, however, appears to be more complex both behaviorally and physiologically. In this review, several complications of the behavior are pointed out, based on a recent computer-graphic analysis of the leg movements. Next described is the cooperative role of several interneurons--not just one--in evoking an escape turn away from the stimulus. A model of this multicellular code for stimulus direction is then presented that correctly predicts the turning behavior under many different experimental conditions. Finally, an overall scheme of the information processing for escape behavior is presented.