Hicks M L, Bacon S P
Department of Speech and Hearing Science, Arizona State University, Tempe 85287-1908, USA.
J Acoust Soc Am. 1999 Sep;106(3 Pt 1):1436-51. doi: 10.1121/1.427146.
Three psychophysical measures of nonlinearity were evaluated before and during a course of aspirin ingestion to investigate the role of outer hair cells (OHCs) in these measures, as aspirin is thought to alter the functioning of OHCs. Six normal-hearing individuals received a moderate dose (3.9 g/day) of aspirin for four days, producing essentially flat, temporary hearing losses that ranged from 5-20 dB. The losses were about 2 dB greater for a 300-ms signal than for a 15-ms signal, indicating reduced temporal integration with aspirin. On the final three days of aspirin use, three experiments were completed; each was designed to measure one aspect of nonlinear behavior: (1) the effects of level on frequency selectivity in simultaneous masking using notched-noise maskers, (2) two-tone suppression using forward maskers at the signal frequency (fs) and suppressor tones above fs, and (3) growth-of-masking functions in forward masking using a masking tone below fs. Signal frequencies of 750 and 3000 Hz were used to evaluate the effects of aspirin at relatively low- and high-frequency regions of the cochlea. In experiment 1, aspirin broadened the auditory filters and reduced the effect of level on frequency selectivity. In experiment 2, aspirin reduced or eliminated two-tone suppression. And, in experiment 3, aspirin reduced the slopes of the growth-of-masking functions. Thus, the aspirin was effective in reducing nonlinearity in all three experiments, suggesting that these measures reflect the same (or a similar) active, nonlinear mechanism, namely the compressive nonlinearity provided by the OHCs. In all experiments, aspirin tended to have larger detrimental effects on the nonlinear measures at 3000 Hz than at 750 Hz, which can be explained in terms of greater involvement of nonlinear processing at higher frequencies. Finally, these effects of aspirin were found to be similar to those observed in preliminary measurements in two subjects with mild, permanent hearing loss.
在服用阿司匹林的疗程前后，对三种非线性的心理物理学测量方法进行了评估，以研究外毛细胞（OHC）在这些测量方法中的作用，因为人们认为阿司匹林会改变OHC的功能。六名听力正常的个体连续四天服用中等剂量（3.9克/天）的阿司匹林，导致基本上呈平坦状的暂时性听力损失，损失范围在5-20分贝之间。对于300毫秒的信号，损失比对15毫秒信号的损失大约大2分贝，这表明阿司匹林会降低时间整合能力。在服用阿司匹林的最后三天，完成了三项实验；每项实验旨在测量非线性行为的一个方面：（1）使用带凹口噪声掩蔽器时，声级对同时掩蔽中频率选择性的影响；（2）使用信号频率（fs）处的前向掩蔽器和高于fs的抑制音进行双音抑制；（3）使用低于fs的掩蔽音进行前向掩蔽时的掩蔽增长函数。使用750赫兹和3000赫兹的信号频率来评估阿司匹林在耳蜗相对低频和高频区域的作用。在实验1中，阿司匹林拓宽了听觉滤波器，并降低了声级对频率选择性的影响。在实验2中，阿司匹林降低或消除了双音抑制。而且，在实验3中，阿司匹林降低了掩蔽增长函数的斜率。因此，在所有三项实验中，阿司匹林都有效地降低了非线性，这表明这些测量方法反映了相同（或相似）的主动非线性机制，即OHC提供的压缩非线性。在所有实验中，阿司匹林对3000赫兹处的非线性测量的有害影响往往比对750赫兹处的更大，这可以从高频处非线性处理的更多参与来解释。最后，发现阿司匹林的这些作用与在两名轻度永久性听力损失受试者的初步测量中观察到的作用相似。
