Neurophysiological Aspects of Song Pattern Recognition and Sound Localization in Grasshoppers

SYNOPSIS. In their intraspecific communication females of the grasshopper Chorthippus biguttulus are able to detect minute gaps in songs. Males of this species can lateralize sound with less than 1 dB difference between the two ears. Behavioral experiments suggested that separate pathways exist for song recognition and sound localization. As for the neurophysiological basis, auditory receptors respond tonically and necessarily carry all information explaining behavioral performances in their spiking responses. However, for pattern recognition as well as for coding of directional information, it seems necessary for the animal to evaluate a whole set of parallel receptor fibres to achieve the precision observed in behavior. The information of receptors converges onto thoracic neurons which drive neurons ascending to the brain. Some of these ascending neurons exhibit dramatic response differences either for various temporal patterns or for sound from different directions and therefore may represent pathways specialized for song recognition or for sound localization.