Karimi Minoo, Farahani Saeid, Nasirinezhad Farinaz, Jalaei Shohreh, Mokrian Helnaz, Shahbazi Ali
Department of Audiology, School of Rehabilitation, Tehran University of Medical Science, Tehran, Iran.
Physiology Research Center, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.
Iran J Basic Med Sci. 2022 Oct;25(10):1177-1182. doi: 10.22038/IJBMS.2022.63698.14083.
Tinnitus is defined as ringing of the ears that is experienced when there is no external sound source, and is an auditory phantom sensation. The insula as a multimodal cortex has been shown to be involved in the processing of auditory stimuli rather than other sensory and motor processing and reported to correlate with some aspects of tinnitus. However, its exact role is not clear. The present study aimed to investigate the effect of excitotoxic lesions limited to the insular cortex on the ability to detect a gap in background noise.
Gap detection test and prepulse inhibition, two objective measurements of auditory startle response, were measured, in 33 male Wistar rats, before and up to four weeks after insular lesion in three experimental groups (sham, control, and lesion).
The ability to detect the gap interposed between 60 db background noise was impaired at weeks 2, 3, and 4 following insular lesion, while prepulse inhibition remained intact up to four weeks after surgery.
These findings indicated that excitotoxic lesions of the insular cortex may produce a tinnitus-like phenomenon in rats while sparing the hearing sensitivity; suggesting that the insular cortex may have a role in the development of tinnitus.
耳鸣被定义为在没有外部声源时所体验到的耳内鸣响，是一种听觉幻觉。脑岛作为一个多模态皮层，已被证明参与听觉刺激的处理，而非其他感觉和运动处理，并据报道与耳鸣的某些方面相关。然而，其确切作用尚不清楚。本研究旨在探讨局限于脑岛皮层的兴奋性毒性损伤对在背景噪声中检测间隙能力的影响。
在三个实验组（假手术组、对照组和损伤组）的33只雄性Wistar大鼠中，在脑岛损伤前及损伤后长达四周测量间隙检测试验和预脉冲抑制，这是听觉惊吓反应的两种客观测量方法。
在脑岛损伤后的第2、3和4周，检测60分贝背景噪声中插入间隙的能力受损，而预脉冲抑制在手术后长达四周仍保持完整。
这些发现表明，脑岛皮层的兴奋性毒性损伤可能在大鼠中产生类似耳鸣的现象，同时保留听力敏感性；提示脑岛皮层可能在耳鸣的发生中起作用。
