Rajan R
Department of Physiology, Monash University, Monash, Vic., Australia.
Audiol Neurootol. 2003 Sep-Oct;8(5):250-62. doi: 10.1159/000071997.
Olivocochlear (OC) pathways have been shown to reduce the temporary threshold shifts (TTSs) caused by traumatic sounds. More recently they have been shown to exacerbate TTSs under certain conditions. One condition is the normal-hearing ear of animals with a chronic unilateral hearing loss. Testing with pure tone trauma showed that then (a) the normal-hearing ear had a lower-than-normal 'intrinsic' susceptibility to intense tones, (b) binaural trauma exacerbated TTSs in the normal-hearing ear through the activity of uncrossed OC (UOC) pathways, and (c) there was no effect on TTSs of the crossed OC (COC) pathway to the normal-hearing ear. The present study is an examination in such animals of effects with noise band trauma. The effects here confirm the previous finding that under such conditions the normal-hearing ear has a lower-than-normal susceptibility to loud sound, and binaural loud sounds exacerbate TTSs in the normal-hearing ear. They extend the previous study by demonstrating that with this traumatic sound, both COC and UOC pathways exacerbate TTSs. These effects contrast against the effects seen in animals with bilaterally normal hearing for the same noise band. Given the commonality of unilateral hearing losses in the normal human population, these data have implications for the functional effects of the OC pathways on loud sound-induced hearing damage.
橄榄耳蜗（OC）通路已被证明可减少由创伤性声音引起的暂时性阈移（TTS）。最近，研究表明在某些情况下，该通路会加剧TTS。其中一种情况是患有慢性单侧听力损失的动物的正常听力耳。纯音创伤测试表明，（a）正常听力耳对高强度音调的“内在”敏感性低于正常水平；（b）双耳创伤通过未交叉的OC（UOC）通路的活动加剧了正常听力耳的TTS；（c）交叉的OC（COC）通路对正常听力耳的TTS没有影响。本研究是对这类动物进行的噪声带创伤影响的检查。这里的结果证实了先前的发现，即在这种情况下，正常听力耳对大声的敏感性低于正常水平，并且双耳大声会加剧正常听力耳的TTS。本研究扩展了先前的研究，表明对于这种创伤性声音，COC和UOC通路都会加剧TTS。这些结果与双侧听力正常的动物在相同噪声带条件下的情况形成对比。鉴于单侧听力损失在正常人群中很常见，这些数据对OC通路在大声引起的听力损伤方面的功能影响具有启示意义。
