Pomberger Thomas, Löschner Julia, Hage Steffen R
Neurobiology of Vocal Communication, Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany.
Graduate School of Neural & Behavioural Sciences - International Max Planck Research School, University of Tübingen, Tübingen, Germany.
Eur J Neurosci. 2020 Sep;52(6):3531-3544. doi: 10.1111/ejn.14721. Epub 2020 Apr 3.
Any transmission of vocal signals faces the challenge of acoustic interferences such as heavy rain, wind, animal or urban sounds. Consequently, several mechanisms and strategies have evolved to optimize signal-to-noise ratio. Examples to increase detectability are the Lombard effect, an involuntary rise in call amplitude in response to masking ambient noise, which is often associated with other vocal changes such as call frequency and duration, as well as the animals' capability of limiting calling to periods where noise perturbation is absent. Previous studies revealed vocal flexibility and various audio-vocal integration mechanisms in marmoset monkeys. Using acoustic perturbation triggered by vocal behaviour, we investigated whether marmosets are capable of exhibiting changes in call structure when perturbing noise starts after call onset or whether such effects only occur if noise perturbation starts prior to call onset. We show that marmosets are capable of rapidly modulating call amplitude and frequency in response to such noise perturbation. Vocalizations swiftly increased call frequency after noise onset indicating a rapid effect of perturbing noise on vocal motor production. Call amplitudes were also affected. Interestingly, however, the marmosets did not exhibit the Lombard effect as previously reported but decreased call intensity in response to noise. Our findings indicate that marmosets possess a general avoidance strategy to call in the presence of ambient noise and suggest that these animals are capable of counteracting a previously thought involuntary audio-vocal mechanism, the Lombard effect. These findings will pave the way to investigate the underlying audio-vocal integration mechanisms explaining these behaviours.
任何声音信号的传输都面临着诸如大雨、风、动物叫声或城市噪音等声学干扰的挑战。因此，已经进化出了几种机制和策略来优化信噪比。提高可探测性的例子包括伦巴德效应，即由于环境噪音的掩盖而导致叫声幅度不由自主地升高，这通常与其他声音变化有关，如叫声频率和时长，以及动物将叫声限制在无噪音干扰时期的能力。先前的研究揭示了狨猴的声音灵活性和各种听觉-发声整合机制。利用由发声行为触发的声学扰动，我们研究了在叫声开始后出现干扰噪音时，狨猴是否能够改变叫声结构，或者这种影响是否仅在噪音干扰在叫声开始之前出现时才会发生。我们发现，狨猴能够响应这种噪音干扰迅速调节叫声的幅度和频率。噪音出现后，叫声迅速提高了频率，这表明干扰噪音对发声运动产生了快速影响。叫声幅度也受到了影响。然而，有趣的是，狨猴并没有表现出先前报道的伦巴德效应，而是在面对噪音时降低了叫声强度。我们的研究结果表明，狨猴在存在环境噪音时具有一种普遍的避免发声策略，并表明这些动物能够对抗一种先前被认为是不由自主的听觉-发声机制——伦巴德效应。这些发现将为研究解释这些行为的潜在听觉-发声整合机制铺平道路。
