Vestibular Response to Sound: Single Unit Recording From the Vestibular Nerve in Fenestrated Deaf Mice (Df/Df)

Abstract

Deaf mice of the Df/Df strain have degenerated cochleas, but histologically normal vestibular structures. After fenestration of the horizontal semicircular canal, tones and clicks were delivered to the fenestrated ears through the external auditory canal using a closed sound system. Single units of the vestibular nerve were picked out by tungsten microelectrodes. Single unit responses were obtained only in fenestrated animals and only for frequencies from 80 to 4200 cycles per second. Threshold was best for 1500 cycles per second and was at 78 db re 0.0002 dynes/cm³. Click responses were also obtained. Some units with the spontaneous activity were driven by tone bursts, others were inhibited. Spontaneous activity was present in single units of non-fenestrated mice, but was not altered by tones or clicks and no units were driven by either type of sound stimulus. The mode of vestibular endorgan stimulation and unit patterns are discussed in light of the present experiments.