The spatial and temporal resolution of bat sonar

超声波回波成像不仅使蝙蝠能够在完全黑暗的复杂环境中定位，而且还能识别空间中复杂的三维物体。当蝙蝠将自然的回声声场景融合在一起时，许多回声将几乎同时从许多不同的方向冲击到蝙蝠的耳朵上。到目前为止，关于蝙蝠从如此众多的回声中分辨出单一反射器的能力，人们还一无所知。在这项拨款建议中，蝙蝠声纳的空间分辨率将在一系列正式的心理物理幻影目标实验中进行研究：在一个六通道、两种选择、强迫选择的设置中，回声定位蝙蝠变色蝙蝠将接受训练，以探测被掩蔽的幻影目标包围的奖励幻影目标。招募多个掩蔽者可以感知地量化声纳空间感受场，并将这些与声纳波束的方向性、蝙蝠外耳的方向性以及电生理测量的时空感受场进行比较。幻影-目标技术不仅允许操纵目标的空间特性，还允许操纵目标和遮蔽物反射的时间和光谱特性。具体地说，将评估信号反射和掩蔽反射之间的回波延迟或频谱内容的差异对空间去掩蔽的贡献。这些实验将详细了解回声定位蝙蝠如何利用其声纳系统的空间特征来检查太空中复杂的回声声学场景。

Ultrasonic echo imaging enables bats not only to orient through complex environments in total darkness, but also to identify complex, three-dimensional objects in space. When a bat ensonifies a natural echo-acoustic scene, many echoes will impinge almost simultaneously from many different directions onto the bats’ ears. To date there is nothing known about the bats’ capability to spatially resolve single reflectors from this multitude of echoes. Within this grant proposal, the spatial resolution of bat sonar is investigated in a series of formal psychophysical phantomtarget experiments: In a six-channel, two-alternative, forced-choice setup, the echolocating bat Phyllostomus discolor will be trained to detect a rewarded phantomtarget surrounded by masking phantom targets. The recruitment of multiple maskers allows quantifying sonar spatial receptive fields perceptually and comparing these with the directionality of the sonar beam, the directionality of the bats’ outer ears, and electrophysiologically measured spatio-temporal receptive fields. The phantom-target technique allows manipulating not only spatial but also temporal and spectral characteristics of the target and masker reflections. Specifically, the contributions of differences in echo delay or spectral content between signal- and masker reflections onto spatial unmasking will be assessed. These experiments will gain a detailed insight into how echolocating bats exploit the spatial characteristics of their sonar system to inspect complex echo-acoustic scenes in space.