Abstract
Electrocochleography (ECochG) to high repetition rate tone bursts may have advantages over ECochG to clicks with standard slow rates. Tone burst stimuli presented at a high repetition rate may enhance summating potential (SP) measurements by reducing neural contributions resulting from neural adaptation to high stimulus repetition rates. To allow for the analysis of the complex ECochG responses to high rates, we deconvolved responses using the Continuous Loop Averaging Deconvolution (CLAD) technique. We examined the effect of high stimulus repetition rate and stimulus duration on SP amplitude measurements made with extratympanic ECochG to tone bursts in 20 adult females with normal hearing. We used 500 and 2,000 Hz tone bursts of various stimulus durations (12, 6, 3 ms) and repetition rates (five rates ranging from 7.1 to 234.38/s). A within-subject repeated measures (rate x duration) analysis of variance was conducted. We found that, for both 500 and 2,000 Hz stimuli, the mean deconvolved SP amplitudes were larger at faster repetition rates (58.59 and 97.66/s) compared to slower repetition rates (7.1 and 19.53/s), and larger at shorter stimulus duration compared longer stimulus duration. Our concluding hypothesis is that large SP amplitude to short duration stimuli may originate primarily from neural excitation, and large SP amplitudes to long duration, fast repetition rate stimuli may originate from hair cell responses. While the hair cell or neural origins of the SP to various stimulus parameters remains to be validated, our results nevertheless provide normative data as a step toward applying the CLAD technique to understanding diseased ears.
Highlights
Electrocochleography (ECochG) is a technique that can be used to objectively assess physiologic properties of the auditory periphery
Oscillations in the waveform can be observed across the slower rates. This pattern was most evident to slower stimulus repetition rates, 7.1 and 19.53/s, but was less evident to increasing rates and not apparent to the fastest rates. This result is consistent with summating potential (SP) oscillations originating from phase-locked neural excitation that adapts to increasing stimulus rate
SP amplitude measures to 2,000 Hz, long duration stimuli increased with increasing repetition rate, as did SP amplitudes to 500 Hz with the longest stimulus duration (12 ms) and highest stimulus repetition rate (58.59/s)
Summary
Electrocochleography (ECochG) is a technique that can be used to objectively assess physiologic properties of the auditory periphery. SP Amplitudes Using CLAD potential (SP)/compound action potential (AP) amplitude ratio, the relatively low sensitivity of this measure alone has limited its diagnostic value for Ménière’s disease (Ferraro and Tibbils, 1999; Ferraro and Durrant, 2006; Al-momani et al, 2009). The lack of sensitivity of the SP/AP ratio measure obtained from click stimuli, and the unknown origins of the disease, has led to the continued refinement of ECochG uses to advance the differential diagnosis of Ménière’s disease. One such method has been the use of tone burst stimuli to assess the SP across frequencies. While the SP and AP can interleave in a given measurement, the amplitude of the SP appears to sustain for the duration of the response and makes it an attractive attribute to study
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