Perceptual Consequences of Early-Onset Hereditary Hearing Loss in the Belgian Waterslager Canary (Serinus Canarius)

Abstract

Belgian Waterslager canaries (BWS) are bred for a distinctive low-pitched song that includes sounds that are thought to resemble water. This strain of canary has been used in multiple neurobiological and behavioral studies of song learning. These birds have a permanent hereditary hearing loss associated with missing and abnormal hair cells. The hearing deficit develops after hatch, but is present when the birds learn their song. The manner in which these birds process complex sounds indisputably affects the content of their vocalizations; however, no studies have looked at BWS canaries' ability to detect and discriminate sounds other than detection of pure tones in quiet. Thus, the BWS canary provides a unique opportunity to investigate the relationship between the form and function of an auditory system involved in vocal learning. Here I describe a series of psychoacoustic experiments that investigate differences in masking, discrimination, temporal processing, and perception of song elements in BWS canaries and normal-hearing non-BWS canary strains. Spectral and temporal studies of masking showed that frequency resolution and the phase response of the basilar papilla are impaired in BWS canaries. Frequency discrimination was superb at low frequencies, but worse than normal at high frequencies in BWS canaries. Duration and intensity discrimination was not adversely affected by the hearing loss. Temporal resolution was normal or better than normal under some conditions in BWS canaries. Despite the hearing loss, BWS canaries are able to accurately discriminate among strain-specific song syllables as well as syllables of other canary strains. In fact, BWS canaries are actually better than non-BWS canaries at discriminating among BWS canary syllables. These perceptual predispositions in BWS canaries are presumably related to the structural abnormalities of the inner ear, and are likely to play a role in song learning and song maintanence by enhancing the birds' ability to attend to important acoustic features that are characteristic of BWS vocalizations.