The effect of interaural timing on the posterior auricular muscle reflex in normal adult volunteers

The posterior auricular muscle (PAM) reflex to sounds has been used clinically to determine hearing threshold as an alternative to other audiological diagnostic measures such as the auditory brainstem response. We have shown that the PAM response is also sensitive to interaural timing differences in normally hearing adults. PAM responses were evoked by both ipsilateral/ contralateral monaural stimulation and by binaural stimulation. Introducing sound delays ipsilaterally or contralaterally decreased the PAM response amplitude and increased its latency. The PAM response in this study shows a qualitatively similar pattern to that seen by the binaural interaction component (BIC) of the auditory brainstem potential to binaural clicks described in previous studies, in that both: have their shortest latency and maximal amplitudes centered around zero interaural timing differences, have response latencies increase with increasing interaural delays up to 1.2 ms and have response amplitudes decrease with increasing interaural delays of up to 1.2 ms. Our data show that the PAM response may be useful in measuring binaural integration in humans non-invasively for diagnostic or research studies.

针对声音刺激的耳后肌（posterior auricular muscle, PAM）反射已在临床中被用作听阈测定的替代诊断手段，可替代听性脑干反应等其他听力学检测方法。本研究团队此前已证实，听力正常成年人的耳后肌反应对双耳时间差同样具有敏感性。本研究中，耳后肌反应可通过同侧/对侧单耳刺激以及双耳刺激诱发。当在同侧或对侧引入声音延迟时，耳后肌反应的振幅会降低，其潜伏期则会延长。本研究测得的耳后肌反应，其定性模式与既往研究中报道的、双耳短声刺激下听觉脑干电位的双耳相互作用成分（binaural interaction component, BIC）高度相似：二者均在双耳时间差为零时呈现最短潜伏期与最大振幅；随着双耳延迟增至1.2毫秒，反应潜伏期均随延迟增加而延长，反应振幅则随延迟增加而降低。本研究数据表明，耳后肌反应可用于无创检测人类的双耳整合功能，适用于临床诊断或相关研究工作。