Ibsen Stuart D, Au Whitlow W L, Nachtigall Paul E, Breese Marlee
Marine Mammal Research Program, Hawaii Institute of Marine Biology, Kailua, Hawaii 96734-1106, USA.
J Acoust Soc Am. 2009 Feb;125(2):1214-21. doi: 10.1121/1.3050274.
The frequency band that an Atlantic bottlenose dolphin (Tursiops truncatus) used to perform an echolocation target discrimination task was determined using computer simulated phantom targets. The dolphin was trained to discriminate frequency filtered phantom targets from unfiltered ones in a go/no-go paradigm. The dolphin's performance indicated perception of echo alteration only when applied filters interfered with the frequency band between 29 and 42 kHz. The dolphin did not behaviorally convey perception of applied filters that affected frequencies outside this functional bandwidth, such as a low pass 43 kHz or a high pass 28 kHz filter. The upper limit of the functional bandwidth at 42 kHz corresponded with the dolphin's upper hearing limit of 45 kHz, as determined through auditory evoked potential measurements. The lower limit of the functional bandwidth corresponded to a drop in intensity below 30 kHz within the dolphin's echolocation clicks. The randomized presentation of different filters showed that the dolphin paid attention to the entire 29-42 kHz band for each trial, not just subsets. The absence of temporal cues between some of the targets the dolphin could discriminate indicated that in these cases the target discrimination cues were based solely on the frequency content.
利用计算机模拟的虚拟目标，确定了大西洋宽吻海豚（瓶鼻海豚）执行回声定位目标辨别任务时所使用的频段。在“是/否”范式中，训练该海豚区分经过频率滤波的虚拟目标和未经过滤波的虚拟目标。海豚的表现表明，只有当所应用的滤波器干扰29至42千赫之间的频段时，它才能感知到回声变化。对于影响该功能带宽以外频率的所应用滤波器，如43千赫低通滤波器或28千赫高通滤波器，海豚并未通过行为表现出对其的感知。通过听觉诱发电位测量确定，功能带宽的上限42千赫与海豚45千赫的听力上限相对应。功能带宽的下限对应于海豚回声定位信号中30千赫以下的强度下降。不同滤波器的随机呈现表明，海豚在每次试验中都关注整个29 - 42千赫频段，而不仅仅是其子集。海豚能够辨别的一些目标之间不存在时间线索，这表明在这些情况下，目标辨别线索仅基于频率内容。
