Neurobiology of acoustically mediated predator detection.

Ultrasound-driven avoidance responses have evolved repeatedly throughout the insecta as defenses against predation by echolocating bats. Although the auditory mechanics of ears and the properties of auditory receptor neurons have been studied in a number of groups, central neural processing of ultrasound stimuli has been examined in only a few cases. In this review, I summarize the neuronal basis for ultrasound detection and predator avoidance in crickets, tettigoniids, moths, and mantises, where central circuits have been studied most thoroughly. Several neuronal attributes, including steep intensity-response functions, high firing rates, and rapid spike conduction emerge as common themes of avoidance circuits. I discuss the functional consequences of these attributes, as well as the increasing complexity with which ultrasound stimuli are represented at successive levels of processing.