Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL.
Department of Psychological Sciences, Loyola University, New Orleans, LA.
J Speech Lang Hear Res. 2018 Nov 8;61(11):2827-2832. doi: 10.1044/2018_JSLHR-H-18-0025.
Understanding speech often involves processing input from multiple modalities. The availability of visual information may make auditory input less critical for comprehension. This study examines whether the auditory system is sensitive to the presence of complementary sources of input when exerting top-down control over the amplification of speech stimuli.
Auditory gain in the cochlea was assessed by monitoring spontaneous otoacoustic emissions (SOAEs), which are by-products of the amplification process. SOAEs were recorded while 32 participants (23 women, nine men; Mage = 21.13) identified speech sounds such as "ba" and "ga." The speech sounds were presented either alone or with complementary visual input, as well as in quiet or with 6-talker babble.
Analyses revealed that there was a greater reduction in the amplification of noisy auditory stimuli compared with quiet. This reduced amplification may aid in the perception of speech by improving the signal-to-noise ratio. Critically, there was a greater reduction in amplification when speech sounds were presented bimodally with visual information relative to when they were presented unimodally. This effect was evidenced by greater changes in SOAE levels from baseline to stimuli presentation in audiovisual trials relative to audio-only trials.
The results suggest that even the earliest stages of speech comprehension are modulated by top-down influences, resulting in changes to SOAEs depending on the presence of bimodal or unimodal input. Neural processes responsible for changes in cochlear function are sensitive to redundancy across auditory and visual input channels and coordinate activity to maximize efficiency in the auditory periphery.
理解言语通常涉及处理来自多种模态的输入。视觉信息的可用性可能会使听觉输入对理解的影响不那么关键。本研究考察了在对言语刺激进行自上而下的控制时，听觉系统是否对互补输入源的存在敏感。
通过监测自发耳声发射（SOAEs）来评估耳蜗中的听觉增益，SOAEs 是放大过程的副产品。当 32 名参与者（23 名女性，9 名男性；Mage=21.13）识别“ba”和“ga”等语音时，记录了 SOAEs。语音声音单独呈现或与互补的视觉输入一起呈现，以及在安静或 6 人 babble 中呈现。
分析显示，与安静相比，嘈杂听觉刺激的放大程度有更大的降低。这种减小的放大可能有助于通过提高信噪比来感知语音。至关重要的是，当语音声音与视觉信息同时呈现时，与仅呈现语音声音时相比，放大程度的降低更大。这一效应表现为，与仅音频试验相比，视听试验中 SOAE 水平从基线到刺激呈现的变化更大。
结果表明，即使是言语理解的最早阶段也受到自上而下的影响的调节，导致根据双模态或单模态输入的存在而改变 SOAEs。负责耳蜗功能变化的神经过程对听觉和视觉输入通道之间的冗余敏感，并协调活动以最大限度地提高听觉外围的效率。
