An auditory interneurone tuned to the male song frequency in the duetting bushcricket Ancistrura nigrovittata (Orthoptera, Phaneropteridae)
An auditory interneurone (AN1) of the bushcricket Ancistrura nigrovittata is described; it has a soma and dendrites in the prothoracic ganglion, an ascending axon and axon collaterals in the protocerebrum. As judged from morphological and physiological similarity, it is probably homologous to AN1 described in Tettigonia viridissima and to AN1 described in Gryllus bimaculatus. The occurrence and physiology of AN1 are not sex-specific. It receives predominant excitation between 12 and 16 kHz (male song frequency) and inhibition at lower frequencies and more strongly at higher frequencies. It shows optimum-type intensity/response curves. Frequency tuning and intensity-dependence compare well with female behaviour. Lesion experiments demonstrate that AN1 receives excitation and frequency-dependent inhibition from the soma-contralateral ear and inhibition from the soma-ipsilateral ear. The latter contributes to the clear left&shy;right difference in its responses. AN1 does not obviously discriminate between temporal patterns of different behavioural effectivity. Its spiking, however, is coupled to the temporal pattern. It is hypothesized that AN1 may be involved in frequency processing by female A. nigrovittata.
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