Ren T, Zhang M, Nuttall A L, Miller J M
Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor, USA.
Acta Otolaryngol. 1995 Nov;115(6):725-31. doi: 10.3109/00016489509139393.
It has been reported that background variation in the frequency of spontaneous otoacoustic emission (SOAEs) may arise from the cardiovascular system and that the side-bands in the spectra of SOAEs may be modulated by heartbeat. For better understanding of the mechanical influence of the cardiac cycle on cochlear functions under physiological and pathophysiological conditions, this study investigated heartbeat-induced modulation of SOAEs in guinea pig. Possible mechanisms of these phenomena are also discussed. The external ear canal acoustic signal, round window electric signal, and the ECG were recorded for off-line analysis from five pigmented guinea pigs with SOAEs. Time and frequency domain averages with synchronization of the heartbeat indicate that both the external ear canal acoustic and round window electric signal contain some component contributed by ECG and phonocardiography. High resolution FFT spectra suggest that SOAEs were modulated by heartbeat and respiration. Theoretically the change in the SOAEs could be from frequency modulation or a combination of frequency and amplitude modulations. Results of a heartbeat-synchronized average of a wave analyzer output at SOAE frequency indicates that amplitude modulation of SOAE does occur. Data obtained in the current experiment support the hypothesis that the heartbeat-related modulation of SOAE in guinea pig is a combination of frequency and amplitude modulation. The proposed mechanism is that pulsatile cochlear blood flow may cause oscillations in cochlear pressure and affect cochlear performance, resulting in heartbeat modulation of SOAEs.
据报道，自发性耳声发射（SOAEs）频率的背景变化可能源于心血管系统，且SOAEs频谱中的边带可能受心跳调制。为了更好地理解在生理和病理生理条件下心动周期对耳蜗功能的机械影响，本研究调查了豚鼠中由心跳引起的SOAEs调制情况。还讨论了这些现象的可能机制。从五只具有SOAEs的有色豚鼠记录外耳道声信号、圆窗电信号和心电图，以供离线分析。心跳同步的时域和频域平均值表明，外耳道声信号和圆窗电信号都包含一些由心电图和心音图贡献的成分。高分辨率快速傅里叶变换（FFT）频谱表明，SOAEs受心跳和呼吸调制。理论上，SOAEs的变化可能来自频率调制或频率与幅度调制的组合。在SOAE频率下对波形分析仪输出进行心跳同步平均的结果表明，SOAE确实存在幅度调制。当前实验获得的数据支持这样的假设，即豚鼠中与心跳相关的SOAE调制是频率和幅度调制的组合。提出的机制是，搏动性耳蜗血流可能导致耳蜗压力振荡并影响耳蜗性能，从而导致SOAEs的心跳调制。
