Pharmacological brain stimulation releases elaborate stridulatory behaviour in gomphocerine grasshoppers - conclusions for the organization of the central nervous control

Grasshoppers produce a variety of sounds generated by complex movements of the hindlegs. Stridulation, performed in the context of partner finding, ma ting and rivalry, call be released by pressure injection of cholinergic ago nists into the protocerebrum. Particularly stimulation with muscarinic agon ists induced long-lasting stridulation that resembled the natural behaviour to an astonishing degree, not only with respect to their temporal structur e and right/left coordination, but also to changes in the song sequences ac cording to the progress of courtship stridulation, even including accessory movements of other parts of the body. According to the complexity of their stridulatory behaviour ten gomphocerine species were chosen for this compa rative study. The results indicate that the protocerebrum fulfils two impor tant tasks in the control of stridulation: (1) it integrates sensory input relevant to stridulation that represents a certain behavioural situation an d internal state of arousal, and (2) it selectively activates and deactivat es the thoracic networks that generate the appropriate movement and sound p atterns. With the knowledge of the natural behaviour and the accessibility to pharmacological and electrophysiological studies, the cephalic control s ystem for stridulation in grasshoppers appears to be a suitable model for h ow the brain selects and controls appropriate behaviours for a given situat ion.