Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2019 Dec;205(6):839-846. doi: 10.1007/s00359-019-01370-0. Epub 2019 Sep 25.
At suprathreshold sound levels, interactions between masking noise and sound signals are liable to compressive nonlinearity in the auditory system. The compressive nonlinearity is a property of the "active" cochlear mechanism. It is not known whether this mechanism is capable to function at frequencies close to or above 100 kHz that are available to odontocetes (toothed whales, dolphins, and porpoises). This question may be answered by the use of the frequency-specific masking. Auditory evoked potentials to sound stimuli in a bottlenose dolphin, Tursiops truncatus, were recorded in the presence of simultaneous maskers. Stimulus frequencies were 45, 64, or 90 kHz. Maskers were on-frequency bandlimited noise or low-frequency noise of frequencies 0.25-1 oct below the stimulus frequency. The stimuli provoked responses as a series of brain-potential waves following the pip-train rate. For the on-frequency masker, the masker level at threshold dependence on the signal level was 1.1 dB/dB. For maskers of 1 oct below the stimulus, the dependence was 0.53-0.57 dB/dB. The data considered evidence for the compressive nonlinearity of responses to stimuli, and therefore, are indicative of the functioning of the active mechanism at frequencies up to 90 kHz.
在阈上声音水平下，掩蔽噪声与声音信号之间的相互作用可能导致听觉系统的压缩非线性。这种压缩非线性是“主动”耳蜗机制的一个特性。目前尚不清楚该机制是否能够在接近或高于齿鲸（齿鲸、海豚和鼠海豚）可用的 100 kHz 的频率下发挥作用。这个问题可以通过使用频率特异性掩蔽来回答。在宽吻海豚（Tursiops truncatus）中，记录了对声音刺激的听觉诱发电位，同时存在掩蔽噪声。刺激频率为 45、64 或 90 kHz。掩蔽噪声是与刺激频率相差 0.25-1 个倍频程的带限噪声或低频噪声。刺激物以一系列跟随脉冲串率的脑电位波引发反应。对于同频掩蔽器，掩蔽器的阈值依赖于信号水平，其依赖关系为 1.1 dB/dB。对于低于刺激频率 1 个倍频程的掩蔽器，其依赖关系为 0.53-0.57 dB/dB。这些数据表明，对刺激的反应存在压缩非线性，因此表明主动机制在高达 90 kHz 的频率下发挥作用。
