Response properties of the prothoracic AN2 auditoryinterneurone to model calling songs in the cricketGryllus bimaculatus

摘要

Sound processing properties for calling song (CS) models, as describedfor the prothoracic L3 auditory neurone in Acheta domesticus, are investigated for thehomologous auditory neurone 2 (AN2) in female Gryllus bimaculatus De Geer. AN2of G. bimaculatus responds selectively to the syllable period (SP) of models of a maleCS. The selectiveness of this response parallels the selectivity of phonotaxis femalesperform in response to the same SPs. Both, the responses of AN2 and female behaviourshow clear interindividual variability. The SP-selective responses of AN2 result froman SP-dependent reduction in the spiking to subsequent syllables of the model CSs,measured as the percentage decrement. This SP-dependent response does not primarilyresult from inbuilt properties of the AN2 membrane. Rather, it is dependent oninhibitory input to the AN2. However, clear inhibitory postsynaptic potentials indendritic recordings of the AN2 are not encountered. This immediate response of AN2to CSs is followed by an increased rate of tonic firing between stimulus CSs, which istermed the prolonged response, and is dependent on the carrier frequencies that makeup the male CSs. With stimulation on the contralateral side of the soma of AN2s, morethan 50% of AN2s exhibit a prolonged response. However, with stimulation from theipsilateral side of the soma, most AN2s exhibit a prolonged response. The prolongedresponse of AN2 at 5 kHz may be even more sensitive than the immediate response.Thus, the AN2 neurone could provide a basis for phonotaxis that is selective for boththe SPs and the carrier frequencies of potentially attractive calling songs.