Modulation rate transfer functions in bottlenose dolphins (Tursiops truncatus) with normal hearing and high-frequency hearing loss
Modulation rate transfer functions in bottlenose dolphins (Tursiops truncatus) with normal hearing and high-frequency hearing loss
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DOI：
10.1007/s00359-007-0238-6
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发表时间：
2007-08-01
影响因子：
2.1
通讯作者：
Houser, Dorian S.
中科院分区：
文献类型：
--
作者：
Finneran, James J.;London, Hollis R.;Houser, Dorian S.
测量了两只宽吻海豚对载波频率为 20 至 60 kHz、调制速率为 100 至 5,000 Hz 的正弦调幅音调的包络跟踪响应。一名受试者在较高频率下的听力阈值较高，受试者之间的阈值差异从 20 和 30 kHz 时的 +/- 4 dB 到 50 和 60 kHz 时的 +40 dB 不等。在每个载波频率处，相对于调制频率绘制诱发响应幅度和相位角，以构建调制率传递函数。结果表明，无论载波频率如何，两名受试者都可以跟踪至少 2,000 Hz 的刺激包络分量。两个受试者的调制率传递函数没有显着差异，这表明听力敏感性的降低不会导致时间处理能力的降低。与早期的研究相比，相位数据显示在测试频率范围内的群延迟约为 3.5 毫秒，这意味着在 100 至 1,600 Hz 的调制速率下，生成位点位于脑干内而不是外周。这种差异被认为是先前相位测量期间调制率采样不足的结果。
Envelope following responses were measured in two bottlenose dolphins in response to sinusoidal amplitude modulated tones with carrier frequencies from 20 to 60 kHz and modulation rates from 100 to 5,000 Hz. One subject had elevated hearing thresholds at higher frequencies, with threshold differences between subjects varying from +/- 4 dB at 20 and 30 kHz to +40 dB at 50 and 60 kHz. At each carrier frequency, evoked response amplitudes and phase angles were plotted with respect to modulation frequency to construct modulation rate transfer functions. Results showed that both subjects could follow the stimulus envelope components up to at least 2,000 Hz, regardless of carrier frequency. There were no substantial differences in modulation rate transfer functions for the two subjects suggesting that reductions in hearing sensitivity did not result in reduced temporal processing ability. In contrast to earlier studies, phase data showed group delays of approximately 3.5 ms across the tested frequency range, implying generation site(s) within the brainstem rather than the periphery at modulation rates from 100 to 1,600 Hz. This discrepancy is believed to be the result of undersampling of the modulation rate during previous phase measurements.