Abstract
This study investigates changes in amplitude and delays in low-frequency toneburst cochlear microphonic (CM) waveforms recorded at the ear canal in response to different stimulus intensities. Ten volunteers aged 20-30 were recruited. Low-frequency CM waveforms at 500 Hz in response to a 14-ms toneburst were recorded from an ear canal electrode using electrocochleography techniques. The data was statistically analyzed in order to confirm whether the differences were significant in the effects of stimulus intensity on the amplitudes and delays of the low-frequency CM waveforms. Electromagnetic interference artifacts can jeopardize CM measurements but such artifacts can be avoided. The CM waveforms can be recorded at the ear canal in response to a toneburst which is longer than that used in ABR measurements. The CM waveforms thus recorded are robust, and the amplitude of CM waveforms is intensity-dependent. In contrast, the delay of CM waveforms is intensity-independent, which is different from neural responses as their delay or latency is intensity-dependent. These findings may be useful for development of the application of CM measurement as a supplementary approach to otoacoustic emission (OAE) measurement in the clinic which is severely affected by background acoustic noise. The development of the application in the assessment of low-frequency cochlear function may become possible if a further series of studies can verify the feasibility, but it is not meant to be a substitute for audiometry or OAE measurements. The measurement of detection threshold of CM waveform responses using growth function approach may become possible in the clinic. The intensity-independent nature of CMs with regards to delay measurements may also become an impacting factor for differential diagnoses and for designing new research studies.
Highlights
IntroductionObjective measurements are important for hearing assessment in the clinic.[1] Audiometry is a subjective measurement
Besides subjective measurements, objective measurements are important for hearing assessment in the clinic.[1]
Based on the information and reasons above, this study explores the possibility of using low-frequency toneburst evoked cochlear microphonic (CM) waveforms as a supplementary approach to otoacoustic emission (OAE) measurements in the clinic by investigating the effects of intensity on such CMs such as their amplitudes and delays
Summary
Objective measurements are important for hearing assessment in the clinic.[1] Audiometry is a subjective measurement. Audiometry plays an important role in hearing assessment. Some other measurements such as otoacoustic emissions (OAEs), cochlear microphonics (CMs) and auditory brainstem responses (ABRs) are objective, and do not rely on the tester’s subjective judgment.[2,3,4,5,6,7,8] While objective measurements cannot completely substitute for audiometry, they are important tools for the clinicians. That is why OAE measurements are frequently used in the clinic because they are often needed for further assessment of cochlear function and for further assessment of various hearing disorders
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