Neurophysiological Aspects of Song Pattern Recognition and Sound Localization in Grasshoppers

SYNOPSIS. In their intraspecific communication females of thegrasshopper Chorthippus biguttulus are able to detect minutegaps in songs. Males of this species can lateralize sound withless than 1 dB difference between the two ears. Behavioral experimentssuggested that separate pathways exist for song recognitionand sound localization. As for the neurophysiological basis,auditory receptors respond tonically and necessarily carry allinformation explaining behavioral performances in their spikingresponses. However, for pattern recognition as well as for codingof directional information, it seems necessary for the animalto evaluate a whole set of parallel receptor fibres to achievethe precision observed in behavior. The information of receptorsconverges onto thoracic neurons which drive neurons ascendingto the brain. Some of these ascending neurons exhibit dramaticresponse differences either for various temporal patterns orfor sound from different directions and therefore may representpathways specialized for song recognition or for sound localization.