Department of Otolaryngology - Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, MSC 550, Charleston, SC 29425, United States.
Hear Res. 2024 Feb;442:108945. doi: 10.1016/j.heares.2023.108945. Epub 2023 Dec 23.
Temporal modulations are ubiquitous features of sound signals that are important for auditory perception. The perception of temporal modulations, or temporal processing, is known to decline with aging and hearing loss and negatively impact auditory perception in general and speech recognition specifically. However, neurophysiological literature also provides evidence of exaggerated or enhanced encoding of specifically temporal envelopes in aging and hearing loss, which may arise from changes in inhibitory neurotransmission and neuronal hyperactivity. This review paper describes the physiological changes to the neural encoding of temporal envelopes that have been shown to occur with age and hearing loss and discusses the role of disinhibition and neural hyperactivity in contributing to these changes. Studies in both humans and animal models suggest that aging and hearing loss are associated with stronger neural representations of both periodic amplitude modulation envelopes and of naturalistic speech envelopes, but primarily for low-frequency modulations (<80 Hz). Although the frequency dependence of these results is generally taken as evidence of amplified envelope encoding at the cortex and impoverished encoding at the midbrain and brainstem, there is additional evidence to suggest that exaggerated envelope encoding may also occur subcortically, though only for envelopes with low modulation rates. A better understanding of how temporal envelope encoding is altered in aging and hearing loss, and the contexts in which neural responses are exaggerated/diminished, may aid in the development of interventions, assistive devices, and treatment strategies that work to ameliorate age- and hearing-loss-related auditory perceptual deficits.
时间调制是声音信号中普遍存在的特征，对听觉感知很重要。随着年龄的增长和听力损失，时间调制的感知或时间处理能力会下降，这会对听觉感知，特别是言语识别产生负面影响。然而，神经生理学文献也提供了证据表明，在衰老和听力损失中，特定的时间包络的编码会被夸大或增强，这可能是由于抑制性神经传递和神经元过度兴奋的变化引起的。
这篇综述文章描述了与年龄和听力损失相关的时间包络神经编码的生理变化，并讨论了去抑制和神经元过度兴奋在这些变化中的作用。在人类和动物模型中的研究表明，衰老和听力损失与周期性幅度调制包络和自然语音包络的更强的神经表示相关，但主要是低频调制（<80 Hz）。尽管这些结果的频率依赖性通常被认为是皮质放大包络编码和中脑和脑干编码贫化的证据，但还有其他证据表明，夸大的包络编码也可能发生在皮质下，尽管仅针对调制率较低的包络。
更好地了解时间包络编码在衰老和听力损失中的变化，以及神经反应被夸大/减弱的情况，可能有助于开发干预措施、辅助设备和治疗策略，以改善与年龄和听力损失相关的听觉感知缺陷。
