Esser K H, Lud B
Abteilung Vergleichende Neurobiologie, Universität Ulm, Germany.
J Comp Physiol A. 1997 May;180(5):513-22. doi: 10.1007/s003590050068.
In the lesser spear-nosed bat, Phyllostomus discolor, maternal directive calls are characterized by an individual type of sinusoidal frequency modulation (= SFM) pattern. Beside modulation frequency, modulation depth, carrier frequency, and number of modulation cycles per call contribute to the mother's vocal signature. Since juvenile P. discolor learn to adapt their isolation calls to the corresponding call characteristics of the own mother or even to playback of a computer-stored directive call, if hand-reared in the absence of conspecifics, the bats' auditory system ought to be able to resolve interindividual differences in communication call structure. However, quantitative psychoacoustic data on the discrimination of SFM signals in this species are not available. Thus, in the present study, lesser spear-nosed bats were trained in a two-alternative forced-choice procedure to discriminate between two alternatingly presented SFM sound signals differing in modulation frequency. Other characteristics of acoustic stimuli were identical and designed to mimick the fundamental of species-specific calls. By gradually reducing the difference in modulation frequency between both stimuli within the behavioural relevant range until the animals' performance dropped below the 75%-correct level, a considerable auditory spectro-temporal resolution has been revealed. Particularly in comparison to the overall interindividual variation of this call parameter (minimal modulation frequency = 49 Hz, maximum = 100 Hz), the determined average difference limen for modulation frequency of 2.42 +/- 0.29 Hz seems substantial and sufficient for labelling individuals.
在小黄肩蝠（Phyllostomus discolor）中，母性指令叫声的特征是一种独特类型的正弦频率调制（=SFM）模式。除了调制频率外，调制深度、载波频率以及每次叫声的调制周期数都构成了母亲的发声特征。由于幼年小黄肩蝠如果在没有同种个体的情况下人工饲养，会学会使它们的隔离叫声适应自己母亲相应的叫声特征，甚至适应计算机存储的指令叫声的回放，所以蝙蝠的听觉系统应该能够分辨出通讯叫声结构中的个体差异。然而，关于该物种对SFM信号辨别能力的定量心理声学数据尚不可得。因此，在本研究中，对小黄肩蝠进行了双选强制选择训练，以区分两个交替呈现的、调制频率不同的SFM声音信号。声学刺激的其他特征相同，并设计成模仿物种特异性叫声的基本特征。通过在行为相关范围内逐渐减小两个刺激之间的调制频率差异，直到动物的表现降至75%正确水平以下，揭示了相当可观的听觉频谱-时间分辨率。特别是与该叫声参数的整体个体间变化（最小调制频率 = 49赫兹，最大 = 100赫兹）相比，所确定的调制频率平均差别阈限为2.42 +/- 0.29赫兹，这似乎足够显著且足以用于识别个体。
