Automatic gain control in the bat's sonar receiver and the neuroethology of echolocation
Automatic gain control in the bat's sonar receiver and the neuroethology of echolocation
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蝙蝠声纳接收器的自动增益控制和回声定位的神经行为学
DOI：
10.1523/jneurosci.04-11-02725.1984
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发表时间：
1984
期刊：
影响因子：
2.9
通讯作者：
J. Simmons
中科院分区：
文献类型：
--
作者：
S. A. Kick;J. Simmons
在两项选择的回声检测实验中测量了回声定位蝙蝠（Eptesicus fuscus）在声纳发射后不同时间延迟时对声纳回声的敏感性。由于回波延迟在感知上等同于目标距离，因此实验有效地测量了对不同距离目标的灵敏度。蝙蝠在发射后仅 1.0 毫秒的短延迟（对应于 17 cm 的范围）检测声纳回波的阈值为 36 dB SPL（峰峰值），但在 6.4 毫秒的较长延迟（对应于 1.1 m 的范围）时，阈值降至 8 dB SPL。先前的研究表明，在更长的延迟（对应于 3 至 5 m 的范围）下，蝙蝠的阈值处于 0 dB SPL 区域。蝙蝠中耳肌肉的收缩与回声定位声音的产生同步，导致听觉灵敏度短暂丧失，这似乎是观察到的回声检测阈值变化的原因。在 17 cm 到 1.1 m 的范围内，目标范围每减少 2 倍，蝙蝠的回声检测阈值就会增加约 11 dB。随着距离缩短，来自小目标的回波幅度也会增加，距离每减少 2 倍，回波幅度就会增加 12 dB。因此，当接近目标时，蝙蝠通过改变其听觉阈值来补偿随着目标范围缩短而产生的回声强度的变化。由于这种补偿似乎发生在中耳，因此蝙蝠在接近飞行昆虫等目标时会将到达耳蜗的回声调节到稳定的幅度。除了这种与目标范围相关的自动增益控制之外，蝙蝠在接近过程中会用头部来跟踪目标的位置，从而即使目标的方向发生变化也能稳定回波幅度。我们假设蝙蝠的定向发射、定向听觉、中耳肌肉收缩和头部瞄准反应共同创建了一个三维空间跟踪滤波器，蝙蝠在拦截猎物期间锁定目标以稳定回声幅度。我们进一步假设，这种调节消除了由目标空间位置变化引起的回声幅度变化，使蝙蝠可以自由地观察由目标自身行为（例如昆虫翅膀拍动）引起的回声幅度变化。消除空间相关的回声幅度变化可以消除神经反应延迟中潜在的麻烦变化的原因，并保持听觉神经纤维调谐曲线“尖端”区域中回声的刺激。（摘要截断为 400 字）
The sensitivity of the echolocating bat, Eptesicus fuscus, to sonar echoes at different time delays after sonar emissions was measured in a two-choice echo detection experiment. Since echo delay is perceptually equivalent to target range, the experiment effectively measured sensitivity to targets at different ranges. The bat's threshold for detecting sonar echoes at a short delay of only 1.0 msec after emissions (corresponding to a range of 17 cm) was 36 dB SPL (peak to peak), but the threshold decreased to 8 dB SPL at a longer delay of 6.4 msec (a range of 1.1 m). Prior research has shown that, at even longer delays (corresponding to ranges of 3 to 5 m), the bat's threshold is in the region of 0 dB SPL. Contractions of the bat's middle ear muscles synchronized with the production of echolocation sounds cause a transient loss in hearing sensitivity which appears to account for the observed echo detection threshold shifts. The bat's echo detection thresholds increase by approximately 11 dB for each reduction in target range by a factor of 2 over the span from 17 cm to 1.1 m. As range shortens, the amplitude of echoes from small targets also increases, by 12 dB for each 2-fold reduction in range. Thus, when approaching a target, the bat compensates for changes in echo strength as target range shortens by changing its hearing threshold. Since this compensation appears to occur in the middle ear, the bat regulates echoes reaching the cochlea to a stable amplitude during its approach to a target such as a flying insect. In addition to this automatic gain control linked to target range, the bat aims its head to track a target's position during approach, thus stabilizing echo amplitude even if the target's direction changes. We hypothesize that the bat's directional emissions, directional hearing, middle ear muscle contractions, and head aim response collectively create a three- dimensional spatial tracking filter which the bat locks onto targets to stabilize echo amplitudes during interception of prey. We further hypothesize that this regulation, which cancels echo amplitude changes caused by the target's changing spatial position, leaves the bat free to observe echo amplitude changes caused by the target's own actions, such as insect wing beats. Elimination of spatially dependent echo amplitude changes removes the cause of potentially troublesome changes in neural response latency and keeps stimulation from echoes in the “tip” region of auditory nerve fiber tuning curves.(ABSTRACT TRUNCATED AT 400 WORDS)