Processing of Species-Specific Signals in the Auditory Pathway of Grasshoppers

Abstract

Species-specific acoustic signals of grasshoppers serve to attract mates; they are pivotal in avoiding hybridisation with sympatric species and to evaluate a potential mate’s quality. This necessitates a high precision of neuronal processing, which is constrained by the noisy nature of neuronal activity. Applying a spike train metric to estimate the variability of auditory responses, we quantified the respective impacts that external degradation of acoustic signals and intrinsic neuronal noise exert on signal processing. Unexpectedly, the variability of spike patterns increases from the afferents to the neurons whose axons ascend to the brain and reduces their ability to discriminate between similar communication signals. Between thoracic local and ascending neurons a change of coding principles seems to occur, leading to a population code with labelled-line characteristics. Thoracic auditory processing is conserved between distantly related species, suggesting that during evolution the communication signals have been adapted to match properties of the receiver’s sensory system.