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The study investigated the time course of the effects of acoustic and electric stimulation on the electrically evoked compound action potential (ECAP). Adult guinea pigs were used in acute experimental sessions. Bursts of acoustic noise and high-rate (5000 pulses/s) electric pulse trains were used as maskers. Biphasic electric pulses were used as probes. ECAPs were recorded from the auditory nerve trunk.Simultaneous masking of the ECAP with acoustic noise featured an onset effect and a decrease in the amount of masking to a steady state. It was characterized by a two-component exponential function. The amount of masking increased with masker level and decreased with probe level. Poststimulatory ECAP recovery often featured a non-monotonic time course, described by a threecomponent exponent. Electric maskers produced similar post-stimulatory effects in hearing and acutely deafened subjects.Acoustic stimulation affects the ECAP in a level-and time-dependent manner. Simultaneous masking follows a time course comparable to that of adaptation to an acoustic stimulus. Refractoriness, spontaneous activity, and adaptation are suggested to play a role in ECAP recovery. Post-stimulatory changes in synchrony, possibly due to recovery of spontaneous activity and an additional hair-cell independent mechanism, are hypothesized to contribute to the observed non-monotonicity of recovery.

Objective: This study aimed to compare effects of increasing the interphase gap (IPG) on the neural response of the electrically-stimulated cochlear nerve (CN) between children with cochlear nerve deficiency (CND) and children with normal-sized CNs. Design: Study participants included 30 children with CND and 30 children with normal-sized CNs. All subjects were implanted with a Cochlear™ Nucleus® device with the internal electrode array 24RE[CA] in the test ear. The stimulus was a charge-balanced, cathodic leading, biphasic pulse with a pulse-phase duration of 50 μs. For each subject, the eCAP input/output (I/O) function was measured for six IPGs (i.e., 7, 14, 21, 28, 35 and 42 μs) at three electrode locations across the electrode array. For each subject and each testing electrode, the highest stimulation used to measure the eCAP I/O function was the maximum comfortable level measured with an IPG of 42 μs. Dependent variables (DVs) were the maximum eCAP amplitude, the eCAP threshold and the slope of the eCAP I/O function estimated using both linear and sigmoidal regression functions. For each DV, the size of the IPG effect was defined as the proportional change relative to the result measured for the 7 μs IPG at the basal electrode location. Generalized Linear Mixed effect Models with subject group, electrode location and IPG duration as the fixed effects and subject as the random effect were used to compare these DVs and the size of the IPG effect on these DVs.

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To date, observations of the scalp-recorded frequency-following response (FFR) to voice pitch have depended on subjective interpretation of the experimenter. The purpose of this study was to develop and evaluate an automated procedure for detecting the presence of a response. Twenty American (9 boys, 1-3 days) and 20 Chinese (10 boys, 1-3 days) neonates were recruited. A Chinese monosyllable that mimicked the English vowel /i/ with a rising pitch (117-166 Hz) was used as the stimulus. Three objective indices (Frequency Error, Tracking Accuracy, and Pitch Strength) were computed from the recorded brain waves and the test results were compared with human judgments to calculate the sensitivity and specificity values. Results demonstrated that the automated procedure produced sensitivity values between 53-90% and specificity values between 80-100%, and could be used to assess the presence of an FFR for neonates who were born in a tonal or non-tonal language environment.