INTERNEURONS PARTICIPATING IN THE ACTIVE REACTION IN STICK INSECTS

The active reaction upon stimulation of the femoral chordotonal organ in stick insects is known to control velocity and endpoint of flexion movements of the femur-tibia joint (Bässler 1988). This article presents evidence that spiking interneurones in the ventral anterior median part of the adjacent ganglion participate in the generation of the active reaction as well as non-spiking interneurones in the dorsal lateral region do. Three different kinds of experiments lead to this conclusion:- Ablation of the ventral anterior median part of the metathoracic ganglion of Extatosoma did not qualitatively alter the resistance reflex in the inactive animal but abolished the active reaction. - Recordings from spiking interneurones in the same region of the prothoracic ganglion of Carausius show that some of these neurones responded to a chordotonal organ stimulus in a way, which depended on the behavioural state of the animal. - Some non-spiking interneurones, which mediate the resistance reflex in the inactive animal, respond differently during an active reaction. © 1990 Springer-Verlag.