Descending control of turning behavior in the cockroach, Blaberus discoidalis

Legged locomotion has evolved as the most effective form of movement through unpredictable and tortuous environments. Upon encountering an obstacle, an animal must evaluate the object with its sense organs then use the information it acquires to direct appropriate transitional behaviors, such as turning. Previous studies using genetic and surgical lesions implicate the central body complex (CBC) in control of such transitional behaviors of various insects. In this study, lesions of the CBC and surrounding brain regions were used to examine the effects of damage on turning in free-moving and tethered cockroaches. Lesions were performed either as sagittal incisions or by inserting small pieces of foil into regions of the brain. Locomotor behaviors of intact and lesioned animals were compared using high speed video and kinematic analysis. The lesions locations were determined through histological methods. Sagittal lesions to the CBC often result in continuous or incorrect turns. Foil lesions in the CBC also increase the probability that individuals will show turning deficits. The location and degree of the lesion had a strong effect on the animal's ability to turn. These data strongly suggest that the CBC mediates the effects of head sense organs that produce changes in the direction of walking.