Karosas Diana M, Gonzales Leslie, Wang Yingxuan, Bergevin Christopher, Carney Laurel H, Henry Kenneth S
Department of Biomedical Engineering, University of Rochester, Rochester, United States.
Department of Neuroscience, University of Rochester, Rochester, United States.
Elife. 2025 Jun 2;13:RP102911. doi: 10.7554/eLife.102911.
Frequency analysis by the cochlea forms a key foundation for all subsequent auditory processing. Stimulus-frequency otoacoustic emissions (SFOAEs) are a potentially powerful alternative to traditional behavioral experiments for estimating cochlear tuning without invasive testing, as is necessary in humans. Which methods accurately predict cochlear tuning remains controversial due to only a single animal study comparing SFOAE-based, behavioral, and cochlear frequency tuning in the same species. The budgerigar () is a parakeet species with human-like behavioral sensitivity to many sounds and the capacity to mimic speech. Intriguingly, previous studies of critical bands, psychophysical tuning curves, and critical ratios in budgerigars show that behavioral tuning sharpness increases dramatically with increasing frequency from 1 to 3.5 kHz, doubling once per octave with peak tuning sharpness from 3.5 to 4 kHz. The pattern contrasts with slower monotonic growth of behavioral tuning sharpness with increasing frequency in other animals, including most avian species, suggesting a possible auditory specialization in budgerigars. We measured SFOAE-based and cochlear-afferent tuning in budgerigars, for comparison to previously reported behavioral results. SFOAE-based and cochlear-afferent tuning sharpness both increased monotonically and relatively slowly for higher frequencies, in contrast to the behavioral pattern. SFOAE-based tuning in budgerigars accurately predicted cochlear frequency tuning, and both measures aligned with typical patterns of cochlear tuning in other species. Divergent behavioral tuning in budgerigars is unlikely attributable to the periphery and could reflect specializations for central processing of masked signals. Our findings highlight the value of SFOAEs for estimating cochlear tuning and caution against direct inference of peripheral tuning from behavioral critical bands, psychophysical tuning curves, and critical ratios.
耳蜗的频率分析是所有后续听觉处理的关键基础。刺激频率耳声发射（SFOAE）是一种潜在的强大替代方法，可用于在无需侵入性测试的情况下估计耳蜗调谐，而这在人类研究中是必要的。由于仅有一项动物研究在同一物种中比较了基于SFOAE的、行为学的和耳蜗频率调谐，因此哪种方法能准确预测耳蜗调谐仍存在争议。虎皮鹦鹉是一种长尾小鹦鹉，对许多声音具有类似人类的行为敏感性，并且有模仿语音的能力。有趣的是，先前对虎皮鹦鹉的临界带宽、心理物理调谐曲线和临界比率的研究表明，行为调谐锐度随着频率从1千赫兹增加到3.5千赫兹而急剧增加，每倍频程翻倍一次，在3.5千赫兹到4千赫兹之间达到峰值调谐锐度。这种模式与其他动物（包括大多数鸟类）中行为调谐锐度随频率增加而缓慢单调增长的情况形成对比，这表明虎皮鹦鹉可能存在听觉特化。我们测量了虎皮鹦鹉基于SFOAE的调谐和耳蜗传入调谐，以便与先前报道的行为学结果进行比较。与行为学模式相反，基于SFOAE的调谐锐度和耳蜗传入调谐锐度在较高频率下均单调且相对缓慢地增加。虎皮鹦鹉基于SFOAE的调谐准确地预测了耳蜗频率调谐，并且这两种测量结果都与其他物种耳蜗调谐的典型模式一致。虎皮鹦鹉中不同的行为调谐不太可能归因于外周，可能反映了对掩蔽信号进行中枢处理的特化。我们的研究结果突出了SFOAE在估计耳蜗调谐方面的价值，并提醒人们不要从行为临界带宽、心理物理调谐曲线和临界比率直接推断外周调谐。
