Gerhardt H Carl, Höbel Gerlinde
Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2005 Aug;191(8):707-14. doi: 10.1007/s00359-005-0626-8. Epub 2005 Jun 1.
Advertisement calls of green treefrogs (Hyla cinerea) have two spectral peaks centered at about 1 kHz and 3 kHz. Addition of a component of intermediate frequency (1.8 kHz) to a synthetic call reduced its attractiveness to females relative to an alternative lacking this component. This mid-frequency suppression occurred over a 20-dB range of playback levels. Addition of other intermediate frequencies had weak effects on preferences at some playback levels, in some localities, and at lower-than-normal temperatures. These effects correlate well with the response properties of a population of low-frequency-tuned auditory neurons innervating the amphibian papilla. Males of a closely related species (H. gratiosa) produce calls with emphasized frequencies within the range of suppression in H. cinerea; however, suppression also occurred in localities well outside the area of geographical overlap with this species. Thus, previous speculation that mid-frequency suppression evolved to enhance species discrimination is probably incorrect. This phenomenon is more likely to reflect a general sensory bias in anurans and other vertebrates, tone-on-tone inhibition. Such negative biases, and other inhibitory mechanisms, almost certainly play an important role in the evolution of communication systems but have received far less attention than positive biases that enhance signal attractiveness.
绿树蛙（雨蛙属）的求偶叫声有两个频谱峰值，分别位于约1千赫兹和3千赫兹处。在合成叫声中添加一个中频成分（1.8千赫兹）会使其对雌性的吸引力相对于缺少该成分的替代叫声降低。这种中频抑制在20分贝的回放水平范围内都会出现。在某些回放水平、某些地点以及低于正常温度的情况下，添加其他中频对偏好的影响较弱。这些影响与支配两栖类乳突的一群低频调谐听觉神经元的反应特性密切相关。一个近缘物种（华丽雨蛙）的雄性发出的叫声中，其强调的频率在灰树蛙的抑制范围内；然而，在与该物种地理重叠区域之外的地方也出现了抑制现象。因此，之前关于中频抑制是为了增强物种辨别能力而进化的推测可能是错误的。这种现象更有可能反映了无尾目动物和其他脊椎动物中一种普遍的感官偏好，即同调抑制。这种负面偏好以及其他抑制机制几乎肯定在通讯系统的进化中起着重要作用，但与增强信号吸引力的正面偏好相比，受到的关注要少得多。
