Perceptual perseverance in a passerine with permanent papillar impairment

Abstract

The Belgian Waterslager canary is unique for its loud, low-pitched song which is accompanied by a hereditary pathology involving missing and damaged hair cells in the basal end of the papilla. These birds were been bred for hundreds of years for loud, low-pitched song. Breeders likely selected for high frequency hearing loss. In spite hair cell regeneration, the papillae in these birds never approaches that of normal-hearing canaries. Auditory nerve and brainstem responses are also diminished, and auditory brainstem nuclei show reduced cell size. And these birds show a suite of psychoacoustic deficits consistent with impaired active processing as seen in humans with hearing loss. It is rather remarkable, then, that Belgian Waterslagers are able to learn, discriminate, and produce complex, species-specific sounds with such impaired frequency selectivity and phase processing. This feat, in the presence of severe peripheral auditory damage, underscores the importance of temporal information in the avian auditory perception and vocal learning. The obvious genetic basis of this pathology places the Belgian Waterslager canary in another unique position of being the only nonhuman organism which must navigate through vocal development and vocal learning in the face of an inherited developmental peripheral auditory pathology.