The Brain and Mind Institute, The University of Western Ontario, London, Ontario N6A 3K7, Canada,
Max Planck Institute for Human Cognitive and Brain Sciences, Magnetoencephalography and Cortical Networks Unit, 04103 Leipzig, Germany, and.
J Neurosci. 2018 Feb 21;38(8):1989-1999. doi: 10.1523/JNEUROSCI.1489-17.2018. Epub 2018 Jan 22.
Optimal perception requires efficient and adaptive neural processing of sensory input. Neurons in nonhuman mammals adapt to the statistical properties of acoustic feature distributions such that they become sensitive to sounds that are most likely to occur in the environment. However, whether human auditory responses adapt to stimulus statistical distributions and how aging affects adaptation to stimulus statistics is unknown. We used MEG to study how exposure to different distributions of sound levels affects adaptation in auditory cortex of younger (mean: 25 years; = 19) and older (mean: 64 years; = 20) adults (male and female). Participants passively listened to two sound-level distributions with different modes (either 15 or 45 dB sensation level). In a control block with long interstimulus intervals, allowing neural populations to recover from adaptation, neural response magnitudes were similar between younger and older adults. Critically, both age groups demonstrated adaptation to sound-level stimulus statistics, but adaptation was altered for older compared with younger people: in the older group, neural responses continued to be sensitive to sound level under conditions in which responses were fully adapted in the younger group. The lack of full adaptation to the statistics of the sensory environment may be a physiological mechanism underlying the known difficulty that older adults have with filtering out irrelevant sensory information. Behavior requires efficient processing of acoustic stimulation. Animal work suggests that neurons accomplish efficient processing by adjusting their response sensitivity depending on statistical properties of the acoustic environment. Little is known about the extent to which this adaptation to stimulus statistics generalizes to humans, particularly to older humans. We used MEG to investigate how aging influences adaptation to sound-level statistics. Listeners were presented with sounds drawn from sound-level distributions with different modes (15 vs 45 dB). Auditory cortex neurons adapted to sound-level statistics in younger and older adults, but adaptation was incomplete in older people. The data suggest that the aging auditory system does not fully capitalize on the statistics available in sound environments to tune the perceptual system dynamically.
最佳感知需要对感官输入进行高效和自适应的神经处理。非人类哺乳动物的神经元会适应声音特征分布的统计特性，从而对环境中最有可能出现的声音变得敏感。然而，人类听觉反应是否会适应刺激的统计分布，以及衰老如何影响对刺激统计的适应，目前尚不清楚。我们使用 MEG 研究了暴露于不同声级分布对年轻（平均年龄：25 岁；n=19）和老年（平均年龄：64 岁；n=20）成年人（男性和女性）听觉皮层适应的影响。参与者被动聆听两种具有不同模式（15 或 45 dB 感觉水平）的声级分布。在具有长刺激间间隔的对照块中，允许神经元群体从适应中恢复，年轻和老年成年人的神经反应幅度相似。关键的是，两个年龄组都表现出对声级刺激统计的适应，但与年轻人相比，老年人的适应发生了变化：在老年组中，在年轻组中完全适应的条件下，神经反应仍然对声级敏感。缺乏对感觉环境统计信息的完全适应可能是老年人难以过滤无关感觉信息的生理机制。行为需要对声音刺激进行有效的处理。动物研究表明，神经元通过根据声音环境的统计特性调整其反应灵敏度来实现高效处理。对于这种对刺激统计的适应在多大程度上适用于人类，特别是老年人，人们知之甚少。我们使用 MEG 研究了衰老如何影响对声级统计的适应。听众被呈现出来自具有不同模式（15 与 45 dB）的声级分布的声音。年轻和老年成年人的听觉皮层神经元适应声级统计，但老年人的适应不完全。数据表明，衰老的听觉系统并没有充分利用声音环境中的统计信息来动态调整感知系统。
