Comparison of the acoustic and neural distortion product at 2f1-f2 in normal-hearing adults.
Input/output functions of the simultaneously recorded acoustic distortion product otoacoustic emissions (DPOAE) and neural frequency following-response distortion products (FFR-DP) at 2f1-f2 were evaluated to determine if these two representations of cochlear nonlinearity exhibit similar response behavior, which would suggest shared cochlear generators. Responses were recorded from normal-hearing adults for a tone burst stimulus pair (F1: 500 Hz; F2: 612 Hz) at 40-70 dB nHL. DPOAE responses were recorded from the ear canal, and FFR responses were recorded differentially from scalp electrodes, representing a vertical configuration. The input/output function for FFR-DP revealed a compressive saturating nonlinearity, whereas the DPOAE input/output function exhibited a linear growth at higher intensities following a compressive behavior at moderate levels. Results appear to suggest that cochlear generators may be contributing differentially to the acoustic and the neural distortion products. Also, FFR-DP responses appeared more identifiable and less variable, particularly at lower stimulus levels, than the corresponding DPOAE. These findings may point to a potential benefit of applying FFR testing to complement DPOAE in evaluating cochlear function at low frequencies.
Auditory Electrophysiology Laboratory, Department of Speech Language and Hearing Sciences, Purdue University, West Lafayette, USA.
Hala
H
Elsisy
Ananthanarayan
A
Krishnan
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001300:Audiometry, Evoked Response; D003056:Cochlear Nerve / Q000502:physiology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005583:Fourier Analysis; D006801:Humans; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D012016:Reference Values