Macular response to auditory stimulation in chinchilla

The purpose of this study was to investigate possible macular response to low frequency sound. While in the presence of a pure tone, the electrical response measured at the vestibule was compared to the electrical response measured at the round window in five chinchilla. The electrical activity at each recording site was noted for 100, 250, 500 and 3000 Hz in increasing 10 dB increments. Input-output functions (IOF's) were constructed for the purpose of comparing response curves from the vestibule electrode to response curves from the round window electrode. Vestibular IOF's generally paralleled the cochlear IOF's for 100, 250, 500 and 3000 Hz. All vestibular readings were lower in output voltage indicating a predominately far-field cochlear response. The cochlear IOF's average voltage for the points of nonlinearity was slightly higher for 3000 Hz than for 100 Hz. However, the average voltage for the points of nonlinearity for 100 Hz vestibular IOF's was almost twice as high as the average voltage for the points of nonlinearity for 3000 Hz vestibular IOF's. Similarly, the mean maximum IOF voltage for 3000 Hz cochlear IOF's was higher than the mean maximum IOF voltage for 100 Hz cochlear IOF's, and vestibular IOF's mean maximum voltage was almost twice as much for 100 Hz than for 3000 Hz. This suggests that the macular areas, when stimulated by low frequency sound may be contributing to the total electrical response obtained at the vestibular electrode. It was concluded the mean results tend to support the theory that low frequency sound does activate the maculae such that small electrophysiological output can be detected. Additionally, these results offer important implications for including vestibular considerations in aural habilitation/rehabilitation.