Schrode Katrina M, Bee Mark A
Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA Department of Ecology, Evolution and Behavior, University of Minnesota, St Paul, MN 55108, USA.
J Exp Biol. 2015 Mar;218(Pt 6):837-48. doi: 10.1242/jeb.115014. Epub 2015 Jan 23.
Sensory systems function most efficiently when processing natural stimuli, such as vocalizations, and it is thought that this reflects evolutionary adaptation. Among the best-described examples of evolutionary adaptation in the auditory system are the frequent matches between spectral tuning in both the peripheral and central auditory systems of anurans (frogs and toads) and the frequency spectra of conspecific calls. Tuning to the temporal properties of conspecific calls is less well established, and in anurans has so far been documented only in the central auditory system. Using auditory-evoked potentials, we asked whether there are species-specific or sex-specific adaptations of the auditory systems of gray treefrogs (Hyla chrysoscelis) and green treefrogs (H. cinerea) to the temporal modulations present in conspecific calls. Modulation rate transfer functions (MRTFs) constructed from auditory steady-state responses revealed that each species was more sensitive than the other to the modulation rates typical of conspecific advertisement calls. In addition, auditory brainstem responses (ABRs) to paired clicks indicated relatively better temporal resolution in green treefrogs, which could represent an adaptation to the faster modulation rates present in the calls of this species. MRTFs and recovery of ABRs to paired clicks were generally similar between the sexes, and we found no evidence that males were more sensitive than females to the temporal modulation patterns characteristic of the aggressive calls used in male-male competition. Together, our results suggest that efficient processing of the temporal properties of behaviorally relevant sounds begins at potentially very early stages of the anuran auditory system that include the periphery.
感觉系统在处理自然刺激（如发声）时功能最为高效，人们认为这反映了进化适应性。在听觉系统进化适应性的最佳描述示例中，无尾目动物（青蛙和蟾蜍）的外周和中枢听觉系统中的频谱调谐与同种叫声的频谱之间经常匹配。对同种叫声时间特性的调谐尚未得到充分证实，在无尾目动物中，迄今为止仅在中枢听觉系统中有记录。我们利用听觉诱发电位，研究灰树蛙（Hyla chrysoscelis）和绿树蛙（H. cinerea）的听觉系统是否存在针对同种叫声中时间调制的物种特异性或性别特异性适应性。由听觉稳态反应构建的调制率传递函数（MRTFs）表明，每个物种对同种求偶叫声典型的调制率比另一个物种更敏感。此外，对配对点击声的听觉脑干反应（ABRs）表明绿树蛙具有相对更好的时间分辨率，这可能代表了对该物种叫声中更快调制率的一种适应。MRTFs以及对配对点击声的ABR恢复在两性之间通常相似，并且我们没有发现证据表明雄性比雌性对雄性间竞争中使用的攻击叫声的时间调制模式更敏感。总之，我们的结果表明，对行为相关声音时间特性的高效处理可能始于无尾目听觉系统包括外周在内的潜在非常早期阶段。
