Blast-induced hearing difficulties affect thousands of veterans and civilians. The long-term impact of even a mild blast exposure on the central auditory system is hypothesized to contribute to lasting behavioral complaints associated with mild blast traumatic brain injury (bTBI). Although recovery from mild blast has been studied separately over brief or long time windows, few, if any, studies have investigated recovery longitudinally over short-term and longer-term (months) time windows. Specifically, many peripheral measures of auditory function either recover or exhibit subclinical deficits, masking deficits in processing complex, real-world stimuli that may recover differently. Thus, examining the acute time course and pattern of neurophysiological impairment using appropriate stimuli is critical to better understanding and intervention of bTBI-induced auditory system impairments. Here, we compared auditory brainstem response, middle-latency auditory evoked potentials, and envelope following responses. Stimuli were clicks, tone pips, amplitude modulated tones in quiet and in noise, and speech-like stimuli (iterated rippled noise pitch contours) in adult male rats subjected to mild blast and sham exposure over the course of two months. We found that blast animals demonstrated drastic threshold increases and auditory transmission deficits immediately after blast exposure, followed by substantial recovery during the window of 7-14 days post-blast, though with some deficits remaining even after two months. Challenging conditions and speech-like stimuli can better elucidate mild bTBI-induced auditory deficit during this period. Our results suggest multiphasic recovery and therefore potentially different time windows for treatment, and deficits can be best observed using a small battery of sound stimuli.

中文翻译：

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轻度爆炸诱发创伤后的纵向听觉病理生理学

爆炸引起的听力困难影响了成千上万的退伍军人和平民。假设即使是轻微的爆炸暴露对中枢听觉系统的长期影响也会导致与轻度爆炸创伤性脑损伤 (bTBI) 相关的持久行为投诉。尽管已经在短期或长期窗口中分别研究了从轻度爆炸中恢复的情况，但很少有研究（如果有的话）对短期和长期（几个月）时间窗口中的恢复进行纵向调查。具体来说，听觉功能的许多外围测量要么恢复要么表现出亚临床缺陷，掩盖了处理可能以不同方式恢复的复杂现实世界刺激的缺陷。因此，使用适当的刺激检查神经生理损伤的急性时间过程和模式对于更好地理解和干预 bTBI 引起的听觉系统损伤至关重要。在这里，我们比较了听觉脑干反应、中潜伏期听觉诱发电位和信封跟随反应。刺激是在两个月内受到轻度爆炸和假暴露的成年雄性大鼠中的咔哒声、音调、安静和噪音中的调幅音调以及类似语音的刺激（重复的波纹噪声音高轮廓）。我们发现，爆炸动物在爆炸暴露后立即表现出急剧的阈值增加和听觉传递缺陷，随后在爆炸后 7-14 天的窗口中显着恢复，尽管即使在两个月后仍有一些缺陷。具有挑战性的条件和类似言语的刺激可以更好地阐明在此期间由 bTBI 引起的轻度听觉缺陷。我们的结果表明多相恢复，因此可能存在不同的治疗时间窗口，并且可以使用少量声音刺激来最好地观察缺陷。