Kakigi A, Hirakawa H, Mount R J, Harrison R V
Department of Otolaryngology, The Hospital for Sick Children, Toronto, Ont., Canada.
Hear Res. 1997 Aug;110(1-2):34-8. doi: 10.1016/s0378-5955(97)00062-2.
The purpose of this study was to investigate the effect of sectioning the crossed olivocochlear bundle (COCB) on transient evoked otoacoustic emissions (TEOAEs) in anesthetized adult chinchillas. Of particular interest is the role of cochlear efferents to the outer haircells (OHCs) and how they control mechanisms responsible for otoacoustic emissions. Specifically the experiment addressed whether a tonic level of inhibitory control is reduced by COCB section. The nonlinear component of TEOAEs was measured before and after COCB section. Analysis was made of the 1, 2, 3, 4, and 5 kHz frequency components and of the total emission, as quantified by fast Fourier transform (FFT) of the raw (time domain) response. After COCB section, the amplitude of the total response and of the 2, 3, 4, and 5 kHz components increased whereas the amplitude of the 1 kHz component decreased. The results indicate that COCB section reduces inhibitory control of the OHC mechanisms responsible for nonlinear TEOAE generation. It is not clear whether the nerve section eliminates a spontaneous level of activity in COCB efferents, or whether it results in the interruption of a stimulus-evoked feedback loop.
本研究的目的是探讨切断交叉橄榄耳蜗束（COCB）对麻醉成年毛丝鼠瞬态诱发耳声发射（TEOAEs）的影响。特别令人感兴趣的是耳蜗传出神经对外毛细胞（OHCs）的作用以及它们如何控制耳声发射的相关机制。具体而言，该实验探讨了切断COCB是否会降低抑制控制的紧张性水平。在切断COCB之前和之后测量TEOAEs的非线性成分。通过对原始（时域）响应进行快速傅里叶变换（FFT），对1、2、3、4和5kHz频率成分以及总发射进行分析。切断COCB后，总响应以及2、3、4和5kHz成分的幅度增加，而1kHz成分的幅度降低。结果表明，切断COCB会降低对负责非线性TEOAEs产生的OHC机制的抑制控制。目前尚不清楚切断神经是消除了COCB传出神经的自发活动水平，还是导致了刺激诱发反馈回路的中断。
