Department of Otolaryngology-Head & Neck Surgery, Medical University of South Carolina, Charleston, SC, USA.
Department of Otolaryngology-Head & Neck Surgery, Medical University of South Carolina, Charleston, SC, USA.
Neurobiol Aging. 2022 Jul;115:50-59. doi: 10.1016/j.neurobiolaging.2022.03.014. Epub 2022 Mar 25.
Aging is associated with auditory nerve (AN) functional deficits and decreased inhibition in the central auditory system, amplifying central responses in a process referred to here as central gain. Although central gain increases response amplitudes, central gain may not restore disrupted response timing. In this translational study, we measured responses putatively generated by the AN and auditory midbrain in younger and older mice and humans. We hypothesized that older mice and humans exhibit increased central gain without an improvement in inter-trial synchrony in the midbrain. Our data demonstrated greater age-related deficits in AN response amplitudes than auditory midbrain response amplitudes, as shown by significant interactions between inferred neural generator and age group, indicating increased central gain in auditory midbrain. However, synchrony decreases with age in both the AN and midbrain responses. These results reveal age-related increases in central gain without concomitant improvements in synchrony, consistent with those predictions based on decreases in inhibition. Persistent decreases in synchrony may contribute to auditory processing deficits in older mice and humans.
衰老与听神经（AN）功能缺陷和中枢听觉系统抑制减弱有关，从而放大了中枢反应，这个过程在这里被称为中枢增益。虽然中枢增益增加了反应幅度，但它可能无法恢复中断的反应时间。在这项转化研究中，我们测量了年轻和老年小鼠和人类中推测由 AN 和听觉中脑产生的反应。我们假设老年小鼠和人类表现出中枢增益增加，而中脑的试验间同步性没有改善。我们的数据表明，与听觉中脑反应幅度相比，AN 反应幅度的年龄相关性下降更大，这表明推断的神经发生器与年龄组之间存在显著的相互作用，表明听觉中脑的中枢增益增加。然而，AN 和中脑反应的同步性都随年龄下降。这些结果揭示了中枢增益的年龄相关性增加，而同步性没有相应改善，这与基于抑制作用减弱的预测一致。同步性的持续下降可能导致老年小鼠和人类的听觉处理缺陷。
