Smotherman M, Metzner W
Department of Physiological Science, UCLA, 621 Charles E. Young Drive S., Box 951606, Los Angeles, CA 90095-1606, USA,
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2003 Jun;189(6):435-46. doi: 10.1007/s00359-003-0422-2. Epub 2003 May 22.
The auditory system of horseshoe bats is narrowly tuned to the sound of their own echoes. During flight these bats continuously adjust the frequency of their echolocation calls to compensate for Doppler-effects in the returning echo. Horseshoe bats can accurately compensate for changes in echo frequency up to 5 kHz, but they do so through a sequence of small, temporally-independent, step changes in call frequency. The relationship between an echo's frequency and its subsequent impact on the frequency of the very next call is fundamental to how Doppler-shift compensation behavior works. We analyzed how horseshoe bats control call frequency by measuring the changes occurring between many successive pairs of calls during Doppler-shift compensation and relating the magnitude of these changes to the frequency of each intervening echo. The results indicate that Doppler-shift compensation is mediated by a pair of (echo)frequency-specific sigmoidal functions characterized by a threshold, a slope, and an upper limit to the maximum change in frequency that may occur between successive calls. The exact values of these parameters necessarily reflect properties of the underlying neural circuitry of Doppler-shift compensation and the motor control of vocalization, and provide insight into how neural feedback can accommodate the need for speed without sacrificing stability.
马蹄蝠的听觉系统对自身回声的声音进行了精细调谐。在飞行过程中，这些蝙蝠会不断调整其回声定位叫声的频率，以补偿返回回声中的多普勒效应。马蹄蝠能够精确补偿高达5千赫兹的回声频率变化，但它们是通过一系列小的、时间上独立的叫声频率阶跃变化来做到这一点的。回声频率与其对紧接着的下一个叫声频率的后续影响之间的关系，对于多普勒频移补偿行为的工作方式至关重要。我们通过测量在多普勒频移补偿期间许多连续叫声对之间发生的变化，并将这些变化的幅度与每个中间回声的频率相关联，来分析马蹄蝠如何控制叫声频率。结果表明，多普勒频移补偿是由一对特定于（回声）频率的S形函数介导的，其特征在于一个阈值、一个斜率以及连续叫声之间可能发生的频率最大变化的上限。这些参数的确切值必然反映了多普勒频移补偿的潜在神经回路和发声运动控制的特性，并为神经反馈如何在不牺牲稳定性的情况下满足速度需求提供了见解。
