Pure-tone audiograms often poorly predict elderly humans’ ability to communicate in everyday complex acoustic scenes. Binaural processing is crucial for discriminating sound sources in such complex acoustic scenes. The compromised perception of communication signals presented above hearing threshold has been linked to both peripheral and central age-related changes in the auditory system. Investigating young and old Mongolian gerbils of both sexes, an established model for human hearing, we demonstrate age-related supra-threshold deficits in binaural hearing using behavioral, electrophysiological, anatomical, and imaging methods. Binaural processing ability was measured as the binaural masking level difference (BMLD), an established measure in human psychophysics. We tested gerbils behaviorally with "virtual headphones," recorded single-unit responses in the auditory midbrain and evaluated gross midbrain and cortical responses using positron emission tomography (PET) imaging. Furthermore, we obtained additional measures of auditory function based on auditory brainstem responses, auditory-nerve synapse counts, and evidence for central inhibitory processing revealed by PET. BMLD deteriorates already in middle-aged animals having normal audiometric thresholds and is even worse in old animals with hearing loss. The magnitude of auditory brainstem response measures related to auditory-nerve function and binaural processing in the auditory brainstem also deteriorate. Furthermore, central GABAergic inhibition is affected by age. Because the number of synapses in the apical turn of the inner ear was not reduced in middle-aged animals, we conclude that peripheral synaptopathy contributes little to binaural processing deficits. Exploratory analyses suggest increased hearing thresholds, altered binaural processing in the brainstem and changed central GABAergic inhibition as potential contributors.

纯音听力图通常很难预测老年人在日常复杂声学场景中的交流能力。双耳处理对于区分如此复杂的声学场景中的声源至关重要。对高于听力阈值的通信信号的感知受损与听觉系统的外周和中枢年龄相关变化有关。通过研究年轻和年老的两性蒙古沙鼠（人类听力的既定模型），我们使用行为、电生理学、解剖学和成像方法证明了与年龄相关的双耳听力阈上缺陷。双耳处理能力通过双耳掩蔽水平差（BMLD）来测量，这是人类心理物理学中的既定测量方法。我们用“虚拟耳机”对沙鼠进行了行为测试，记录了听觉中脑的单个单元反应，并使用正电子发射断层扫描（PET）成像评估了总体中脑和皮质反应。此外，我们还根据听觉脑干反应、听觉神经突触计数以及 PET 显示的中枢抑制处理证据获得了听觉功能的额外测量结果。在听力阈值正常的中年动物中，BMLD 已经恶化，而在听力损失的老年动物中，BMLD 甚至更严重。与听觉脑干中的听觉神经功能和双耳处理相关的听觉脑干反应测量的幅度也会恶化。此外，中枢 GABA 能抑制受到年龄的影响。由于中年动物内耳尖转的突触数量并未减少，因此我们得出结论，外周突触病对双耳处理缺陷的影响很小。探索性分析表明，听力阈值的增加、脑干双耳处理的改变以及中枢 GABA 抑制的改变是潜在的因素。