| The amplitudes of evoked potentials in animals have been reported in the literature to be increased by the occurrence of hearing loss (Gerken, Simhadri-Sumithra, & Bhat, 1986; Popelar, Syka, & Berndt, 1987; Syka & Rybalko, 2000; Syka, Rybalko, & Popelar, 1994). Increased evoked potential amplitudes are believed to be associated with an increase in the neural responsiveness of the central auditory system. However, increased amplitudes on evoked potentials in cases of hearing loss have been difficult to observe in humans. Yet, many theories of tinnitus perception assume that increased neural responsiveness exists in humans with hearing loss. Previously, Gerken & Hesse, (1998) failed to find any differences in evoked potential amplitudes between normal hearing human subjects and hearing-impaired human subjects.; The purpose of this study was to evaluate central auditory functioning in males with high-frequency, sensorineural hearing loss using evoked potential methodology. Specifically, I was looking for indications of increased neural responsiveness in the central auditory systems of hearing-impaired subjects. The two main subject groups consisted of fourteen normal hearing males and fourteen males with high-frequency, sensorineural hearing loss. The subjects were evaluated using auditory brainstem response (ABR) and middle latency response (MLR) evoked potentials. Evoked potentials were elicited using monaural stimulation at four toneburst frequencies and four intensities.; Analysis of variance revealed a significant group effect for a component of the MLR (Pa-Na), with steeper slopes for the normal hearing group. There was also a trend toward a significant group effect for another MLR component (Pb-Nb). Two sample t-tests performed for each stimulus frequency for Pb-Nb revealed a statistically significantly greater mean slope at an important stimulus frequency for the hearing-impaired group. This frequency was the frequency of the “audiometric edge” where the subjects' hearing changed from normal to impaired. |
