Finneran James J, Mulsow Jason, Houser Dorian S
U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center Pacific, Code 71510, 53560 Hull Street, San Diego, California 92152.
National Marine Mammal Foundation, 2240 Shelter Island Drive, #200, San Diego, California 92106.
J Acoust Soc Am. 2013 Dec;134(6):4532. doi: 10.1121/1.4826179.
Studies with echolocating odontocetes have suggested that forms of automatic gain control mediate auditory electrophysiological responses to target-related echoes. This study used a phantom echo generator and auditory evoked potential measurements to examine automatic gain control in a bottlenose dolphin. Auditory evoked potentials to outgoing clicks and incoming echoes were recorded for simulated ranges from 2.5 to 80 m. When geometric spreading loss was simulated, echo-evoked potential amplitudes were essentially constant up to 14 m and progressively decreased with increasing range. When the echo levels were held constant relative to clicks, echo-evoked potential amplitudes increased with increasing range up to 80 m. These results suggest that automatic gain control maintains distance-independent echo-evoked potential amplitudes at close range, but does not fully compensate for attenuation due to spreading loss at longer ranges. The automatic gain control process appears to arise from an interaction of transmitter and receiver based processes, resulting in a short-range region of distance-independent echo-evoked potential amplitudes for relevant targets, and a longer-range region in which echo-evoked potential amplitudes are reduced.
对使用回声定位的齿鲸类动物的研究表明，自动增益控制机制介导了对目标相关回声的听觉电生理反应。本研究使用了一个模拟回声发生器和听觉诱发电位测量来检测宽吻海豚的自动增益控制。针对2.5至80米的模拟距离，记录了对发出的滴答声和返回回声的听觉诱发电位。当模拟几何扩展损耗时，回声诱发的电位幅度在14米以内基本保持恒定，并随着距离增加而逐渐降低。当回声水平相对于滴答声保持恒定时，回声诱发的电位幅度随着距离增加而增加，直至80米。这些结果表明，自动增益控制在近距离保持与距离无关的回声诱发电位幅度，但在较长距离时不能完全补偿由于扩展损耗引起的衰减。自动增益控制过程似乎源于发射器和接收器相关过程的相互作用，导致在相关目标的近距离区域出现与距离无关的回声诱发电位幅度，而在较长距离区域回声诱发电位幅度降低。
