Inferior colliculus single unit responses to peripheral electrical stimulation in normal and congenitally deaf mice

We have investigated the single unit response in the inferior colliculus of the mouse to electrical pulse stimulation at the auditory periphery. The experimental animals were deafness mutant mice (dn/dn), which have hereditary congenital peripheral pathology. The control animals were normal littermates (+/dn). Monopolar electrical pulses were applied either to the modiolus or the round window and the evoked single unit activity was recorded in the contralateral inferior colliculus (IC). Two types of single unit response were observed: a single-spike response, and a multiple-spike response. There was a predominance of the former in the control animals and of the latter in the mutants. For both modes of stimulation the group mean threshold of response was lower in mutants compared to controls, whilst the maximum number of evoked spikes per 50 presentations was higher in mutants than control animals. The mutant response pattern was similar to that seen in animals with experimentally induced auditory deprivation. The suitability of the deafness mutant as a model for the investigation of coding strategies for cochlear implants is discussed.