Effects of contralateral acoustical stimulation on three measures of cochlear function in the guinea pig

The magnitudes of suppression of the click-evoked compound action potential of the auditory nerve (CAP), transient click-evoked otoacoustic emissions (TEOAEs) and ensemble background activity of the auditory nerve (EBA), elicited by contralateral acoustical stimulation, were compared in awake or lig...

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Bibliographic Details
Published in:Hearing research 2001-02, Vol.152 (1), p.128-138
Main Authors: Popelár, Jirı́, Erre, Jean-Paul, Syka, Josef, Aran, Jean-Marie
Format: Article
Language:English
Subjects:
Acoustic Stimulation - methods
Action Potentials - physiology
Animals
Auditory nerve
Biological and medical sciences
Cochlea - physiology
Cochlear Nerve - physiology
Compound action potential
Contralateral suppression
Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation
Electrophysiology
Ensemble background activity
Functional Laterality
Fundamental and applied biological sciences. Psychology
Guinea pig
Guinea Pigs
Transient otoacoustic emissions
Vertebrates: nervous system and sense organs
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Summary:The magnitudes of suppression of the click-evoked compound action potential of the auditory nerve (CAP), transient click-evoked otoacoustic emissions (TEOAEs) and ensemble background activity of the auditory nerve (EBA), elicited by contralateral acoustical stimulation, were compared in awake or lightly sedated guinea pigs. The contralateral ear was stimulated either by continuous broad-band noise or by low-pass or high-pass noise (intensity 41–62 dB SPL) with cut-off frequencies of 2, 8 and 12 kHz. The maximal suppression of TEOAEs was achieved by contralateral noise containing mainly low frequencies, whereas for suppression of the CAP it was necessary for middle frequencies to be present in the contralateral noise (less than 8 kHz). In contrast to this, EBA was suppressed mainly by high-frequency noise (higher than 8 kHz) whereas low- and middle-frequency noise was ineffective in suppressing EBA. Evaluation of the root mean square voltage of the EBA (filtered in frequency range 0.75–1.25 kHz) enabled the evaluation of fast and slow components of olivocochlear activation. Both fast and slow effects were proportionally suppressed by individual types of contralateral stimulation. The mechanisms of TEOAEs and CAP generation has been confirmed in many earlier studies, but the origin of EBA has yet to be fully elucidated. The obtained data support the hypothesis that a large part of EBA is formed by spontaneous activity of high-frequency-tuned auditory nerve fibres. Suppression of the EBA magnitude during contralateral stimulation may be caused either by a reduced spontaneous firing rate or by a decrease in possible synchronised neuronal firing.
ISSN:0378-5955
1878-5891
DOI:10.1016/S0378-5955(00)00244-6