Conservation of the ´individuality´ of communication signals by the sensory neurons

Sexual selection is one of the major forces driving the evolution of communication systems. To be selective, animals must be able to evaluate differences between the signals of conspecific individuals. On the part of the receiver this implies a signal analysis far more subtle than the mere acceptance of conspecific (and rejection of heterospecific) signals. The ultimate hurdle to this task is imposed by neural noise sources that could mask small but relevant differences of the communication signals. Here it is reported for the first time that even slight variations among conspecific communication signals can be faithfully encoded by the sensory periphery. Analyzing the responses of auditory receptor neurons to grasshopper mating calls, it is shown that a few spikes from a single neuron suffice to distinguish two calling songs. This ability is made possible by the receptor´s remarkable resolution of the song´s amplitude modulation patterns and serves to provide important information about the sender´s reproductive quality.