Echolocating big brown bats (Eptesicus fuscus) perceive their surroundings by broadcasting frequency-modulated (FM) ultrasonic pulses and processing returning echoes. Bats echolocate in acoustically-cluttered environments containing multiple objects, where each broadcast is followed by multiple echoes at varying time delays. The bat must decipher this complex echo cascade in order to form a coherent picture of the entire acoustic scene. Neurons in the bat's inferior colliculus (IC) are selective for specific acoustic features of echoes and time delays between broadcasts and echoes. Because of this selectivity, different subpopulations of neurons are activated as the bat flies through its environment, while the physical scene itself remains unchanging. We asked how a neural representation based on variable single neuron responses could underly a cohesive perceptual representation of a complex scene. We recorded local field potentials from the IC of big brown bats to examine population coding of echo cascades similar to what the bat might encounter when flying alongside vegetation. We found that the temporal patterning of a simulated broadcast followed by an echo cascade is faithfully reproduced in the population response at multiple stimulus amplitudes and echo delays. Local field potentials to broadcasts and echo cascades undergo amplitude-latency trading consistent with single neuron data but rarely show paradoxical latency shifts. Population responses to the entire echo cascade move as a unit coherently in time as broadcast-echo cascade delay changes, suggesting that these responses serve as an index for the formation of a cohesive perceptual representation of an acoustic scene.

中文翻译：

---

大棕蝙蝠听觉中脑回声流的种群登记

回声定位大棕色蝙蝠 (Eptesicus fuscus) 通过广播调频 (FM) 超声波脉冲和处理返回的回声来感知周围环境。蝙蝠在包含多个物体的声学杂乱环境中进行回声定位，其中每次广播之后都会有不同时间延迟的多个回声。蝙蝠必须破译这个复杂的回声级联，以形成整个声学场景的连贯画面。蝙蝠下丘 (IC) 中的神经元对回声的特定声学特征以及广播和回声之间的时间延迟具有选择性。由于这种选择性，当蝙蝠飞过其环境时，不同的神经元亚群被激活，而物理场景本身保持不变。我们询问基于可变单个神经元响应的神经表示如何成为复杂场景的凝聚感知表示的基础。我们记录了来自大型棕色蝙蝠 IC 的局部场电位，以检查回声级联的种群编码，类似于蝙蝠在与植被一起飞行时可能遇到的情况。我们发现，模拟广播后跟回声级联的时间模式在多个刺激幅度和回声延迟的群体响应中忠实再现。广播和回波级联的局部场电位经历与单个神经元数据一致的幅度延迟交易，但很少显示出矛盾的延迟变化。随着广播回声级联延迟的变化，群体对整个回声级联的响应作为一个单元在时间上连贯地移动，