Saunders J C, Torsiglieri A J, DeDio R M
Department of Otorhinolaryngology and Human Communication, University of Pennsylvania, Philadelphia.
Hear Res. 1993 Sep;69(1-2):25-34. doi: 10.1016/0378-5955(93)90090-n.
One-day-old chicks were exposed to an intense pure tone (0.9 kHz, 120 dB SPL) and assigned to one of eight groups based on continuous exposure durations from 1 to 200 h. As each animal was removed from the exposure, it was anesthetized and an electrode was placed in the nucleus magnocellularis. Sound-evoked potentials were used to measure absolute thresholds and frequency selectivity. Thresholds were measured at 10 frequencies between 0.1 and 4.5 kHz while frequency selectivity was assessed by a simultaneous masking tuning-curve procedure at five probe-tone frequencies between 0.3 and 2.5 kHz. Threshold shift was greatest at 1.3 kHz and reached a maximum loss of approximately 57 dB between 48 and 200 h of exposure. The shape of the threshold-shift curve as a function of exposure duration (for frequencies between 0.9 and 2.5 KHz) suggested the presence of an early and late effect. The loss in tuning sharpness was evaluated by comparing the values of Q10 dB for control and exposed tuning curves and expressing the difference between them as a percent change. Probe-tone tuning curves above 0.9 kHz became less selective as exposure duration increased. A maximum decrease in tuning of about 54 percent was reached by 48 h and this remained constant to 200 h. The low-frequency tuning curves (below 0.9 kHz) did not show any systematic loss in selectivity. The changes in sensitivity and selectivity are discussed in relation to the patterns of cochlear injury that occurred on the basilar papilla as exposure duration lengthened.
将一日龄雏鸡暴露于高强度纯音（0.9千赫兹，120分贝声压级）下，并根据1至200小时的连续暴露时长将其分为八组。每只动物从暴露环境中取出后，进行麻醉，然后将电极置于巨细胞核中。使用声诱发电位来测量绝对阈值和频率选择性。在0.1至4.5千赫兹之间的10个频率处测量阈值，同时通过在0.3至2.5千赫兹之间的五个探测音频率处进行的同时掩蔽调谐曲线程序来评估频率选择性。阈值偏移在1.3千赫兹时最大，在暴露48至200小时之间达到约57分贝的最大损失。阈值偏移曲线作为暴露时长的函数（对于0.9至2.5千赫兹之间的频率）表明存在早期和晚期效应。通过比较对照和暴露调谐曲线的Q10分贝值并将它们之间的差异表示为百分比变化来评估调谐锐度的损失。随着暴露时长增加，高于0.9千赫兹的探测音调谐曲线选择性降低。到48小时时，调谐最大降低约54%，并在200小时时保持不变。低频调谐曲线（低于0.9千赫兹）在选择性上未显示出任何系统性损失。结合随着暴露时长延长在基底乳头发生的耳蜗损伤模式，讨论了敏感性和选择性的变化。
