Stanley A. Gelfand

Long-Term Effects of Monaural, Binaural and No Amplification in Subjects with Bilateral Hearing Loss

This study expands upon our earlier work by comparing initial PB scores and audiometric thresholds with results obtained 4-17 years later for subjects with bilateral sensorineural hearing losses who were monaurally aided (n = 48), binaurally aided (n = 19), or unaided (n = 19). Thresholds decreased slightly for all groups, but aided and unaided ears did not differ significantly in this respect, revealing no acoustic trauma effect due to hearing aid use. PB scores decreased significantly only for the unaided ear of the monaurally aided subjects, but not for their aided ear, or for the binaurally aided or unaided groups. These findings suggest an auditory deprivation effect for the unaided ear of those wearing a monaural hearing aid. Changes in PB scores were not correlated with duration between the two test dates. Changes in PB scores were correlated with degree of hearing loss only for the unaided group.

A proposed model for the acoustic reflex

A qualitative model based upon the relative contributions of the inner and outer hair cells is proposed as a parsimonious basis for acoustic reflex behavior in response to tonal and broad‐band activators in normal and impaired ears. It calls upon the localized, divergent innervation of the inner hair cells (IHCs); and the convergent; specially distributed innervation of the outer hair cells (OHCs), which have lower thresholds but are more susceptible to damage than the IHCs. The OHCs are viewed as the basis for the lower reflex threshold, bandwidth effect, and the curvilinear portion of the reflex growth function for broad‐band activators in normals. The elevated reflex threshold, and the absence of both the bandwidth effect and the curvilinear portion of the growth function for broad band activators in impaired ears is attributed to the absence/damage of OHCs. The total reflex thresholds in normals and in mildly impaired ears, as well as the linear growth functions for tones and the linear portion of the...