Summary:
Evoked otoacoustic emissions can be detected in the majority of subjects with normal
hearing. They are used currently in the diagnosis of peripheral hearing disorders and are used also
in audiological research. Extensive clinical research is impossible without a background of experi-
mental modelling of pathological conditions in laboratory animals. The authors elaborated a method
for EOAE examination in guinea pigs using the ILO 92 apparatus. It was revealed that the response
depends to a considerable extent on parameters of assessment. For examination of TEOAE in guinea
pigs stimulation by a non-linear click with intensities up to 75 dB SPL and an averaging window of
1.5-10 ms is best. For examination of DPOAE the authors recommend stimulation with intensities
LI = 55 dB SPL, L2 = 45 dB SPL, ratio of frequencies f2/f1 = 1.209. The intravital origin of thus
obtained EOAE responses was tested by post-mortem experiments. TEOAE produced by a click with
an intensity of 74.4 dB SPL could not be elicited even after one minute. DPOAE 55/45 three minutes
after extinction of respiration. Conversely DPOAE elicited by primaries 70/70 persisted for at least
14 minutes after extinction of cardiac activity. The authors found furthermore in a group of guinea
pigs that contralateral acoustic stimulation by broad-spectrum noise with an intensity of 61 dB SPL
has a comparable effect on TEOAE as electric stimulation of the contralateral oval window. Sup-
pression of the amplitude of TEOAE on average by 0.87 ± 0.55 dB and 0.79 ± 0.87 dB resp. occurred.
Electric stimulation of the ipsilateral colliculus inferior did not produce a significant effect. Possible
suppression of TEOAE by contralateral electric stimulation of the round window is a model suitable
for research of the function of the efferent system.
Key words:
evoked otoacoustic emissions, contralateral acoustic and electric suppression, guinea
pig.
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