KU Leuven - University of Leuven, Department of Neurosciences, Experimental Oto-Rhino-Laryngology, Belgium.
Ear Hear. 2018 Mar/Apr;39(2):260-268. doi: 10.1097/AUD.0000000000000483.
Auditory steady state responses (ASSRs) are used in clinical practice for objective hearing assessments. The response is called steady state because it is assumed to be stable over time, and because it is evoked by a stimulus with a certain periodicity, which will lead to discrete frequency components that are stable in amplitude and phase over time. However, the stimuli commonly used to evoke ASSRs are also known to be able to induce loudness adaptation behaviorally. Researchers and clinicians using ASSRs assume that the response remains stable over time. This study investigates (1) the stability of ASSR amplitudes over time, within one recording, and (2) whether loudness adaptation can be reflected in ASSRs.
ASSRs were measured from 14 normal-hearing participants. The ASSRs were evoked by the stimuli that caused the most loudness adaptation in a previous behavioral study, that is, mixed-modulated sinusoids with carrier frequencies of either 500 or 2000 Hz, a modulation frequency of 40 Hz, and a low sensation level of 30 dB SL. For each carrier frequency and participant, 40 repetitions of 92 sec recordings were made. Two types of analyses were used to investigate the ASSR amplitudes over time: with the more traditionally used Fast Fourier Transform and with a novel Kalman filtering approach. Robust correlations between the ASSR amplitudes and behavioral loudness adaptation ratings were also calculated.
Overall, ASSR amplitudes were stable. Over all individual recordings, the median change of the amplitudes over time was -0.0001 μV/s. Based on group analysis, a significant but very weak decrease in amplitude over time was found, with the decrease in amplitude over time around -0.0002 μV/s. Correlation coefficients between ASSR amplitudes and behavioral loudness adaptation ratings were significant but low to moderate, with r = 0.27 and r = 0.39 for the 500 and 2000 Hz carrier frequency, respectively.
The decrease in amplitude of ASSRs over time (92 sec) is small. Consequently, it is safe to use ASSRs in clinical practice, and additional correction factors for objective hearing assessments are not needed. Because only small decreases in amplitudes were found, loudness adaptation is probably not reflected by the ASSRs.
听觉稳态响应（ASSR）在临床实践中用于客观听力评估。该响应之所以被称为稳态，是因为它被假设在时间上是稳定的，并且因为它是由具有一定周期性的刺激引起的，这将导致离散的频率分量在时间上稳定的幅度和相位。然而，用于诱发 ASSR 的刺激也被认为能够在行为上引起响度适应。使用 ASSR 的研究人员和临床医生假设响应随时间保持稳定。本研究调查了（1）在一次记录中 ASSR 幅度随时间的稳定性，以及（2）响度适应是否可以反映在 ASSR 中。
来自 14 名正常听力参与者的 ASSR 进行了测量。ASSR 是由之前行为研究中引起最大响度适应的刺激诱发的，即载波频率为 500 或 2000 Hz 的混合调制正弦波、调制频率为 40 Hz 且低感觉水平为 30 dB SL。对于每个载波频率和参与者，进行了 40 次 92 秒记录的重复。使用两种类型的分析来研究 ASSR 幅度随时间的变化：更传统的快速傅里叶变换和新的卡尔曼滤波方法。还计算了 ASSR 幅度与行为响度适应评分之间的稳健相关性。
总体而言，ASSR 幅度是稳定的。在所有个体记录中，幅度随时间的中位数变化为-0.0001 μV/s。基于组分析，发现幅度随时间有一个显著但非常微弱的下降，幅度随时间的下降约为-0.0002 μV/s。ASSR 幅度与行为响度适应评分之间的相关系数是显著的，但低到中等，对于 500 和 2000 Hz 载波频率，相关系数分别为 r = 0.27 和 r = 0.39。
ASSR 幅度随时间（92 秒）的下降很小。因此，在临床实践中可以安全地使用 ASSR，并且不需要用于客观听力评估的额外校正因子。由于仅发现幅度的小幅下降，因此响度适应可能不会反映在 ASSR 中。
