Abdelatti Zainab A S, Hartbauer Manfred
Institute of Zoology, Karl-Franzens University Graz, Universitätsplatz 2, 8010, Graz, Austria; Department of Zoology, South Valley University, 83523, Qena, Egypt.
Institute of Zoology, Karl-Franzens University Graz, Universitätsplatz 2, 8010, Graz, Austria.
Hear Res. 2017 Nov;355:70-80. doi: 10.1016/j.heares.2017.09.011. Epub 2017 Sep 21.
In forest clearings of the Malaysian rainforest, chirping and trilling Mecopoda species often live in sympatry. We investigated whether a phenomenon known as stochastic resonance (SR) improved the ability of individuals to detect a low-frequent signal component typical of chirps when members of the heterospecific trilling species were simultaneously active. This phenomenon may explain the fact that the chirping species upholds entrainment to the conspecific song in the presence of the trill. Therefore, we evaluated the response probability of an ascending auditory neuron (TN-1) in individuals of the chirping Mecopoda species to triple-pulsed 2, 8 and 20 kHz signals that were broadcast 1 dB below the hearing threshold while increasing the intensity of either white noise or a typical triller song. Our results demonstrate the existence of SR over a rather broad range of signal-to-noise ratios (SNRs) of input signals when periodic 2 kHz and 20 kHz signals were presented at the same time as white noise. Using the chirp-specific 2 kHz signal as a stimulus, the maximum TN-1 response probability frequently exceeded the 50% threshold if the trill was broadcast simultaneously. Playback of an 8 kHz signal, a common frequency band component of the trill, yielded a similar result. Nevertheless, using the trill as a masker, the signal-related TN-1 spiking probability was rather variable. The variability on an individual level resulted from correlations between the phase relationship of the signal and syllables of the trill. For the first time, these results demonstrate the existence of SR in acoustically-communicating insects and suggest that the calling song of heterospecifics may facilitate the detection of a subthreshold signal component in certain situations. The results of the simulation of sound propagation in a computer model suggest a wide range of sender-receiver distances in which the triller can help to improve the detection of subthreshold signals in the chirping species.
在马来西亚雨林的林间空地上，发出啁啾声和颤鸣声的硕螽科物种常常同域分布。我们研究了一种被称为随机共振（SR）的现象是否能提高个体在异种颤鸣物种的成员同时活跃时检测啁啾典型低频信号成分的能力。这一现象或许可以解释为何在有颤鸣声存在的情况下，啁啾物种仍能维持对同种鸣声的同步。因此，我们评估了发出啁啾声的硕螽科物种个体中一个上升听觉神经元（TN - 1）对三重脉冲2千赫、8千赫和20千赫信号的反应概率，这些信号在低于听觉阈值1分贝的情况下播放，同时增加白噪声或典型颤鸣歌声的强度。我们的结果表明，当周期性的2千赫和20千赫信号与白噪声同时呈现时，在输入信号的相当广泛的信噪比（SNR）范围内存在随机共振。以特定啁啾的2千赫信号作为刺激，如果同时播放颤鸣声，TN - 1的最大反应概率常常超过50%的阈值。播放颤鸣声的一个常见频带成分8千赫信号，也产生了类似的结果。然而，以颤鸣声作为掩蔽声时，与信号相关的TN - 1尖峰概率变化较大。个体水平上的这种变化源于信号相位关系与颤鸣音节之间的相关性。这些结果首次证明了在进行声学通讯的昆虫中存在随机共振，并表明异种的求偶歌声在某些情况下可能有助于检测阈下信号成分。计算机模型中声音传播的模拟结果表明，在很宽的发送者 - 接收者距离范围内，颤鸣者能够帮助提高啁啾物种对阈下信号的检测能力。
