RESPONSE SELECTIVITY FOR MULTIPLE DIMENSIONS OF FREQUENCY SWEEPS IN THE PALLID BAT INFERIOR COLLICULUS
RESPONSE SELECTIVITY FOR MULTIPLE DIMENSIONS OF FREQUENCY SWEEPS IN THE PALLID BAT INFERIOR COLLICULUS
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DOI：
10.1152/jn.1994.72.3.1061
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发表时间：
1994-09-01
影响因子：
2.5
通讯作者：
FUZESSERY, ZM
中科院分区：
文献类型：
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作者：
FUZESSERY, ZM
1.在狩猎时，苍白蝙蝠使用低频的被动声音定位来寻找陆地猎物，并使用回声定位来确定大致方向。因此，它必须同时处理两种不同类型的声学输入。苍白蝙蝠的回声定位脉冲是一个向下的调频（FM）扫描从60到30千赫。本研究探讨了单一神经元的反应选择性苍白的蝙蝠的下丘（ICC）的中央核FM扫描，比较的响应特性的高频人口，调谐到生物声纳脉冲，与低频人口，调谐低于脉冲。工作假设是，高频人群将表现出对向下FM扫描的响应选择性，这在低频人群中不存在。测试神经元对FM扫描方向、持续时间、频率范围和带宽以及频率变化率的选择性。在何种程度上，他们专门回应音调，噪音，调频扫描也进行了检查。两组神经元的反应特性有显著差异，低频组所有神经元对音调有反应，但只有50%的神经元对FM扫频有反应。只有23%的人选择了扫描方向。在高频人群中，所有的神经元都对FM扫描有反应，但31%的神经元对音调没有反应。超过一半的人对扫描方向有选择性，而那些有选择性的人，都喜欢生物声纳脉冲的向下扫描方向。很大一部分（31%）只对向下的扫频做出反应，而不是对音调或向上的扫频做出反应。两个群体中的细胞都没有对噪声作出反应，或者只有在非常高的相对阈值下才有反应。这两个群体都含有对短刺激持续时间具有选择性的神经元，这些短刺激持续时间近似于生物声纳脉冲的持续时间，尽管高频群体中的百分比更大（58%对20%）。在高频群体中，31%的神经元只对生物声纳脉冲的扫描方向和持续时间做出反应。向下的FM选择性神经元，有一个例外，一般不敏感的频率变化率的FM扫描，以及频率范围和带宽的扫描。它们对60至30 kHz全扫描和全扫描的5 kHz带宽部分的响应相似。在整个记录人口的神经元的百分比，专门向下FM扫描近似的生物声纳脉冲的反应是一个数量级大于已报告的IC的大多数其他蝙蝠研究。这表明，这种选择性不是简单地选择性探测生物声纳回波所必需的。相反，这种苍白的蝙蝠听觉中脑的极端功能专门化可能满足了同时处理主动和被动声学信息的需求。所观察到的响应选择性可以起到维持用于回声定位和被动收听的两个平行通道之间的分离的作用。
1. While hunting, the pallid bat uses passive sound localization at low frequencies to find terrestrial prey, and echolocation for general orientation. It must therefore process two different types of acoustic input at the same time. The pallid bat's echolocation pulse is a downward frequency-modulated (FM) sweep from 60 to 30 kHz. This study examined the response selectivity of single neurons in the pallid bat's central nucleus of the inferior colliculus (ICC) for FM sweeps, comparing the response properties of the high-frequency population, tuned to the biosonar pulse, with the low-frequency population, tuned below the pulse. The working hypothesis was that the high-frequency population would exhibit a response selectivity for downward FM sweeps that was not present in the low-frequency population.2. Neurons were tested for their selectivity for FM sweep direction, duration, frequency range and bandwidth, and rate of frequency change. The extent to which they responded exclusively to tones, noise, and FM sweeps was also examined. Significant differences in the response properties of neurons in the two populations were found. In the low-frequency population, all neurons responded to tones, but only 50% responded to FM sweeps. Only 23% were selective for sweep direction. In the high-frequency population, all neurons responded to FM sweeps, but 31% did not respond to tones. Over one-half of this population was selective for sweep direction, and of those that were selective, all preferred the downward sweep direction of the biosonar pulse. A large percentage (31%) responded exclusively to downward sweeps, and not to tones or upward sweeps. None of the cells in either population responded to noise, or did so only at very high relative thresholds.3. Both populations contained neurons that were selective for short stimulus durations that approximated the duration of the biosonar pulse, although the percentage was greater in the high-frequency population (58% vs. 20%). In the high-frequency population, 31% of the neurons tested for duration responded exclusively to both the sweep direction and duration of the biosonar pulse.4. Downward FM-selective neurons, with one exception, were generally insensitive to the rate of frequency change of the FM sweep, as well as the frequency range and bandwidth of the sweep. They responded similarly to both the full 60- to 30-kHz sweep and to 5-kHz bandwidth portions of the full sweep.5. The percentage of neurons in the entire recorded population that responded exclusively to downward FM sweeps approximating the biosonar pulse is an order of magnitude greater than has been reported in the IC of most other bats studied. This suggests that such selectivity is not needed simply for the selective detection of biosonar echoes. Instead, this extreme functional specialization in the pallid bat auditory midbrain may serve the demands of having to process active and passive acoustic information at the same time. The response selectivity observed may function to maintain the separation between two parallel channels for echolocation and passive listening.