Adaptation and spectral enhancement at auditory temporal perceptual boundaries - Measurements via temporal precision of auditory brainstem responses

In human and animal auditory perception the perceived quality of sound streams changes depending on the duration of inter-sound intervals (ISIs). Here, we studied whether adaptation and the precision of temporal coding in the auditory periphery reproduce general perceptual boundaries in the time domain near 20, 100, and 400 ms ISIs, the physiological origin of which are unknown. In four experiments, we recorded auditory brainstem responses with five wave peaks (P1 –P5) in response to acoustic models of communication calls of house mice, who perceived these calls with the mentioned boundaries. The newly introduced measure of average standard deviations of wave latencies of individual animals indicate the waves’ temporal precision (latency jitter) mostly in the range of 30–100 μs, very similar to latency jitter of single neurons. Adaptation effects of response latencies and latency jitter were measured for ISIs of 10–1000 ms. Adaptation decreased with increasing ISI duration following exponential or linear (on a logarithmic scale) functions in the range of up to about 200 ms ISIs. Adaptation effects were specific for each processing level in the auditory system. The perceptual boundaries near 20–30 and 100 ms ISIs were reflected in significant adaptation of latencies together with increases of latency jitter at P2-P5 for ISIs

在人类与动物的听觉感知中，听觉流的感知质量会随声间间隔（inter-sound intervals, ISIs）的时长发生变化。本研究旨在探讨听觉外周的适应现象与时间编码精度，是否能够复现时域中约20 ms、100 ms与400 ms ISIs处的通用感知边界——该边界的生理起源目前尚不明确。我们通过四项实验，以小家鼠通讯叫声的声学模型作为听觉刺激，记录到包含P1-P5五个波峰的听觉脑干反应（auditory brainstem responses）；而小家鼠正是依托前述感知边界来识别此类叫声的物种。本研究新引入的个体动物波峰潜伏期平均标准差指标，可反映各波的时间精度（潜伏期抖动（latency jitter）），其测量值多处于30–100 μs区间，与单个神经元的潜伏期抖动水平高度相似。我们针对10–1000 ms的声间间隔，测量了反应潜伏期与潜伏期抖动的适应效应。当声间间隔时长处于约200 ms以内的区间时，适应效应随时长增加呈指数函数或对数尺度下的线性函数衰减规律。听觉系统不同加工层级所表现出的适应效应具有特异性。ISIs约20–30 ms与100 ms处的感知边界，可通过P2-P5波峰潜伏期的显著适应效应，以及伴随的潜伏期抖动升高现象得到体现。