Abstract:
Electrocochleography can be used in estimating conditions for both cochlea and auditory nerve, while ABR is for nerve and otoacoustic emission (OAE)
is only for cochlea. Further, ECochG is affected by forward transmission, resulting in lower threshold than OAEs (Zhang & Abbas, 1997). ECochG,
obtained from the electrode closer to the generator, has an action potential greater than that in ABR. Therefor, ECochG is important in clinical audiology
and deserves more studies. Electrodes for ECochG vary in configurations. TMtrodes (Tympanic Mambrane electrodes, Ferraro & Durrant, 2002 in Katz) can be better in
many aspects than invasive TTtrodes (TransTympanic); while ECtrodes (Ear Canal) could generate usable responses based on the previous reports. However, the
advantages of ECtrode and the recordings with it in response to tonebursts have not been completely addressed yet. We did recordings in response to click and
tonebursts such as of 2000 Hz. In comparison, the N1 amplitude with ECtrode could be up to about half of that with TMtrode. To the click, wave III & V
were also displayed but the amplitude ratio of N1/V was larger than that in ABR. To a 14-ms 2000-Hz toneburst, the CM (cochlear microphonic) and N1
were observed, while wave III and V were not. Since the signal to noise ratio obtained with ECtrode is smaller than with TMtrode, it is critical
to avoid several pitfalls including the cross talk. Compared with TMtrode, we found ECtrode can have at least eight advantages including zero loads
on tympanic membrane. We will extend this study in several aspects, such as cochlear microphonic distortion products (Zhang & Abbas, 1997).