A neuroethological analysis of the information in propagated communication calls

Abstract

The detection and recognition of communication signals in natural soundscapes is a difficult task that animals and birds in particular excel at. We have used a neuroethological approach to quantify the recognition performance for propagated communication signals in the zebra finch, specifically regarding the information about individual identity. The propagated signals were analyzed using a regularized discriminant function analyses on a complete spectrographic representation of the signals. We found (1) a reduction in the informative frequency range a long distances yielding a frequency band sweet-spot, (2) that call duration and pitch are important parameters at short distances, and (3) that frequency modulation gains are important parameters at longer distances. Operant conditioning experiments showed that female songbirds were able to discriminate male calls at up to 128 m but not at 256 m. Finally, neurophysiological recordings showed a similar pattern in that high neural discrimination for calls was observed at 16 m and that this information degraded as a function of distance. We are currently analyzing the tuning properties of neurons that showed the most invariant responses to propagated sounds and hypothesized that these will be tuned to the parameters that we found were the most informative in the discriminant function analysis.