Sound source elevation and external ear cues influence the discrimination of spectral notches by the big brown bat, Eptesicus fuscus.
Sound source elevation and external ear cues influence the discrimination of spectral notches by the big brown bat, Eptesicus fuscus.
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DOI：
10.1121/1.416073
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发表时间：
1996-09
期刊：
影响因子：
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通讯作者：
J. Wotton;T. Haresign;M. Ferragamo;J. Simmons
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文献类型：
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作者：
J. Wotton;T. Haresign;M. Ferragamo;J. Simmons
在回声定位蝙蝠Eptesicus fuscus中的外耳传递函数的测量揭示了中心频率（50至30-35 kHz）随着海拔降低而降低的显著频谱陷波[沃顿等人，J. Acoust.美国社会98，1423-1445（1995）]。为了检验这个缺口的影响，四个Eptesicus被训练来区分两组电子生成的人工回波。负（无奖励）刺激包含一个测试频谱缺口在一个特定的频率，从30到50 kHz的变化，而积极的（奖励）刺激不包含测试缺口。扬声器的垂直位置每天都在改变，以传递这些模拟回声。当回声是从一个高度返回的，在这个高度外耳引入了一个与测试陷波频率相同的频谱陷波，那么辨别应该是困难的。蝙蝠的表现符合这一预测：所有蝙蝠在除-10度以外的所有海拔高度都能分辨出35 kHz的缺口。随着合成缺口频率的增加，蝙蝠无法进行辨别的海拔也增加了。蝙蝠的“盲点”的运动，不同频率的测试缺口遵循的外耳缺口在不同的高度的运动。
Measurements of external ear transfer functions in the echolocating bat Eptesicus fuscus have revealed a prominent spectral notch that decreases in center frequency (50 to 30-35 kHz) as elevation decreases [Wotton et al., J. Acoust. Soc. Am. 98, 1423-1445 (1995)]. To examine the influence of this notch, four Eptesicus were trained to discriminate between two sets of electronically generated artificial echoes. The negative (unrewarded) stimulus contained a test spectral notch at a specific frequency that varied from 30 to 50 kHz, while the positive (rewarded) stimulus contained no test notch. The vertical position of the loudspeakers delivering these simulated echoes was changed daily. When echoes were returned from an elevation at which the external ear introduced a spectral notch at the same frequency as the test notch, then the discrimination should have been difficult. The bats' performance conformed to this prediction: All bats discriminated the presence of a 35-kHz notch at all elevations except -10 degrees. As the frequency of the synthesized notch increased, the elevation at which bats could not perform the discrimination also increased. The movement of the bat's "blind spot" for the test notch of different frequencies followed the movement of the external ear notch at different elevations.