Frequency encoding in field crickets

Abstract

We have studied the properties of auditory interneurons in field crickets as they relate to the encoding of frequency information in communication signals. Tungsten microelectrodes were used to record from single units in the neuropil of the prothoracic ganglion of the Australian field cricket, Teleogryllus oceanicus. Based on their maximal frequency sensitivity, four types of tonic, short-latency units were found: (1) 5-kHz units with ipsilateral input; (2) 5-kHz units with contralateral input; (3) broadly tuned 15-kHz units; and (4) 5-kHz units which are inhibited by frequencies below their best excitatory frequency. Thus information encoded in “labelled lines” was available at this level of the auditory system for both gross frequency discrimination between 5 and 15 kHz and fine frequency discrimination near 5kHz. The possibility also exists for latency encoding of frequencies near 5kHz due to the frequency-specific latency of the last type of interneuron listed.