Informational masking of vocal signals in a nonhuman animal

Abstract

Informational masking (IM) interferes with speech perception in the presence of multiple talkers. However, its impact on vocal communication in other animals has received little attention. This talk will present behavioral and neurophysiological evidence—much of it preliminary, circumstantial, or both—suggesting that frogs are also susceptible to IM in the context of vocal communication in noisy social environments. When choosing a mate in a chorus, female treefrogs must extract information related to a male’s suitability and quality as a mate from the temporal envelope of his vocalizations. In behavioral experiments, temporally structured maskers constrain a female’s ability to process the temporal envelopes of target vocalizations, even when targets and maskers are sufficiently different in frequency to be transduced by different inner ear papillae. (The frog’s peripheral auditory system—consisting of multiple sensory papillae that encode different frequency ranges of airborne sound—provides a natural “spectral protection zone” for minimizing the impacts of energetic masking in experimental studies of IM.) In neurophysiological experiments, potential correlates of IM can be observed in the responses of single neurons in the inferior colliculus. Future work will employ a multi-tone masking paradigm to determine how spatial separation, masker uncertainty, and target-masker similarity impact “subcortical” signal processing mechanisms in the context of IM and vocal communication.