Salloom William B, Bharadwaj Hari, Strickland Elizabeth A
University of Southern California.
University of Pittsburgh.
Res Sq. 2025 Jun 2:rs.3.rs-6753082. doi: 10.21203/rs.3.rs-6753082/v1.
Measures of the human medial olivocochlear reflex (MOCR) typically rely on long duration (>100 ms) or continuously presented broadband elicitors. MOCR gain reduction measured by otoacoustic emissions (OAE) exhibits multiple time constants, including in the hundreds of milliseconds, when elicited by broadband noise. Psychoacoustic studies of gain reduction have largely adopted these elicitor characteristics, but less is known about how broadband elicitor duration affects auditory perception. Additionally, the literature on the relationship between psychoacoustic and OAE measures of gain reduction has yielded mixed results, which is counterintuitive if both measures reflect the same mechanism. In this study, the effects of ipsilateral broadband elicitor duration were evaluated using forward masking psychoacoustic and transient-evoked OAE (TEOAE) paradigms in individuals with normal hearing.
Ipsilateral pink broadband noise was used as the elicitor in both experiments, presented at 50 dB SPL (50-800 ms) for the psychoacoustic measures and 50 dB FPL (50-400 ms) for the TEOAE measures. Gain reduction was quantified as the change in signal threshold (2 kHz) and the change in TEOAE level (1/3-octave band centered at 2 kHz) with and without the presence of the elicitor.
The average time constants for psychoacoustic and TEOAE gain reduction were similarly short (<100 ms), with near-maximal effects observed for elicitor durations of 200 ms. However, individual comparisons of TEOAE and psychoacoustic gain reduction revealed mixed results. Potential factors contributing to this discrepancy are discussed.
The human MOCR reduces cochlear gain on relatively short time scales (<100 ms) with ipsilateral broadband elicitors.
人类内侧橄榄耳蜗反射（MOCR）的测量通常依赖于长时间（>100毫秒）或持续呈现的宽带刺激源。通过耳声发射（OAE）测量的MOCR增益降低在由宽带噪声诱发时呈现多个时间常数，包括数百毫秒。增益降低的心理声学研究在很大程度上采用了这些刺激源特征，但对于宽带刺激源持续时间如何影响听觉感知知之甚少。此外，关于增益降低的心理声学测量与OAE测量之间关系的文献得出了不一致的结果，如果这两种测量反映的是相同机制，这是违反直觉的。在本研究中，使用前掩蔽心理声学和瞬态诱发耳声发射（TEOAE）范式对听力正常的个体评估同侧宽带刺激源持续时间的影响。
在两个实验中均使用同侧粉红宽带噪声作为刺激源，心理声学测量时以50 dB SPL呈现（50 - 800毫秒），TEOAE测量时以50 dB FPL呈现（50 - 400毫秒）。增益降低被量化为有和没有刺激源时信号阈值（2千赫）的变化以及TEOAE水平（以2千赫为中心的1/3倍频程带）的变化。
心理声学和TEOAE增益降低的平均时间常数同样较短（<100毫秒），在刺激源持续时间为200毫秒时观察到接近最大的效应。然而，TEOAE和心理声学增益降低的个体比较结果不一。讨论了导致这种差异的潜在因素。
人类MOCR在相对较短的时间尺度（<100毫秒）上通过同侧宽带刺激源降低耳蜗增益。
