Ganz M, von Specht H, Kevanishvili Z
Medizinische Fakultät, Universitätsklinik für Hals-, Nasen- und Ohrenheilkunde, Abteilung für Experimentelle Audiologie und Medizinische Physik, Otto-von-Guericke-Universität Magdeburg.
Laryngorhinootologie. 1997 May;76(5):278-83. doi: 10.1055/s-2007-997427.
In recent publications the influence of contralateral white noise on transient evoked otoacoustic emissions (TEOAE) is discussed with regard on contributions of the efferent auditory system.
In the present study the effects have been investigated with regards to middle-ear muscles, efferents and cross hearing. TEOAE to monaural 40-80 dB SPL clicks were recorded in normal-hearing adults under simultaneous presentation of 20-60 dB SPL broadband noise to the contralateral ear. Control runs were performed before, during a short break of, and after contralateral stimulation. The control run before contralateral stimulation was used as a reference.
Decrease in TEOAE, and increase in accompanying noise floor, were found to follow the contralateral stimulation. In particular a 1-3 dB decrease was found for contralateral noise levels of 40 and 60 dB SPL, even though the readings at 60 dB only were statistically significant (paired-samples t test, p = 0.05). For both TEOAE and noise floor no systematic dependence on click intensity was seen. The control runs during temporary break and after contralateral noise revealed an increase in both TEOAE and noise floor. As a rule, the TEOAE adapted to the reference within 2-3 min following the cessation of contralateral stimulation, whereas the increased noise floor level was still noted after 10 min.
Traditionally, suppressing effects of contralateral stimulation on TEOAE have been attributed to cochlear efferents (CEs). Occasionally, the middle-ear muscle and cross hearing involvement have been considered as well. Substantially, the present results and findings of other workers are inconsistent with the basic knowledge of CE functioning: (I) The decrease in TEOAE under contralateral stimulation is in conflict with an increase in cochlear microphonics and summating potentials observed during activation of CEs: (II) contralateral suppression of TEOAE exhibited no significant dependence on the test-stimulus level while the CEs are known to be efficient in the range of the low signal intensities only, and (III) acoustic activation of the CEs can hardly be expected to reach levels sufficient to influence the TEOAE mechanism. The present findings, i.e. decrease in TEOAE and increase in noise floor level, can more reasonably be explained as being mainly attributable to activation of the middle-ear muscles.
在最近的出版物中，关于传出听觉系统的贡献，讨论了对侧白噪声对瞬态诱发耳声发射（TEOAE）的影响。
在本研究中，针对中耳肌肉、传出神经和交叉听力对这些影响进行了研究。在正常听力的成年人中，向对侧耳同时呈现20 - 60 dB SPL的宽带噪声时，记录对单耳40 - 80 dB SPL短声的TEOAE。在对侧刺激之前、短暂中断期间和之后进行对照测试。将对侧刺激前的对照测试用作参考。
发现对侧刺激后TEOAE降低，伴随的本底噪声增加。特别是对于40和60 dB SPL的对侧噪声水平，发现TEOAE降低了1 - 3 dB，尽管仅60 dB时的读数具有统计学意义（配对样本t检验，p = 0.05）。对于TEOAE和本底噪声，均未观察到对短声强度的系统性依赖。在短暂中断期间和对侧噪声之后的对照测试显示TEOAE和本底噪声均增加。通常，对侧刺激停止后2 - 3分钟内TEOAE适应参考水平，而本底噪声水平升高在10分钟后仍可观察到。
传统上，对侧刺激对TEOAE的抑制作用归因于耳蜗传出神经（CEs）。偶尔也会考虑中耳肌肉和交叉听力的影响。实际上，本研究结果和其他研究人员的发现与CE功能的基本知识不一致：（I）对侧刺激下TEOAE的降低与CE激活期间观察到的耳蜗微音电位和总和电位的增加相矛盾；（II）TEOAE的对侧抑制对测试刺激水平无明显依赖性，而CEs仅在低信号强度范围内有效；（III）几乎无法预期CEs的声学激活能达到足以影响TEOAE机制的水平。本研究结果，即TEOAE降低和本底噪声水平升高，更合理的解释是主要归因于中耳肌肉的激活。
