Neuronal processing of complex sounds in the prothoracic ganglion of a bushcricket.

Male bushcrickets produce complex species-specific songs to attract mating partners. Since the neuronal processing underlying song-pattern detection is not fully understood, we analysed extracellularly recorded song-induced spike responses and local field potentials across the first stage of auditory processing in the prothoracic ganglion of Mecopoda elongata. We analysed the influence of the temporal structure and of any change in amplitude of spiking and local field potentials. We presented the complete chirp and compared the neuronal response pattern with those responses evoked individually by each pulse of the chirp. Our data revealed: (i) the complete chirp leads to a transient summation in local field potentials over the time course of the chirp, and (ii) significantly fewer action potentials occur during the chirp presentation than to the individually presented pulses. Our data provide insights into the question of how an acoustical signal can be used to extract those features from sensory information that are important for auditory behaviour, such as chorus formation, species recognition, or phonotaxis.