Natural echolocation sequences evoke echo-delay selectivity in the auditory midbrain of the FM bat, Eptesicus fuscus
Natural echolocation sequences evoke echo-delay selectivity in the auditory midbrain of the FM bat, Eptesicus fuscus
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DOI：
10.1152/jn.00160.2018
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发表时间：
2018-09-01
影响因子：
2.5
通讯作者：
Moss, Cynthia F.
中科院分区：
文献类型：
--
作者：
Macias, Silvio;Luo, Jinhong;Moss, Cynthia F.
回声定位蝙蝠必须处理声纳声音的时间流来表示沿距离轴的物体。神经元回声延迟调谐是声纳测距的假定机制，已在胡须蝙蝠的下丘 (IC) 中得到表征，胡须蝙蝠是一种食虫物种，可产生由恒定频率和调频 (FM) 成分组成的回声定位呼叫，但在单独使用 FM 信号的物种中则不然。这引发了关于使用不同信号设计的食虫蝙蝠中产生回声延迟调谐的机制的问题。为了研究刺激环境是否可以解释回声延迟选择性的物种差异，我们表征了清醒被动聆听调频蝙蝠（Eptesicus fuscus）的 IC 中对自然声纳呼叫回声序列广播的单个单元响应，其中包含信号持续时间、间隔、频谱时间结构和回声延迟的动态变化。在 E. fuscus 中，当用模拟自然声纳序列的间隔出现的呼叫回声对刺激时，IC 神经元群体中会出现对呼叫回声延迟的神经选择性。为了确定回声延迟选择性是否也取决于自然声纳序列中单个声音的频谱时间特征，我们研究了对控制呼叫间隔、持续时间、带宽、扫描速率和回声延迟的计算机生成的回声定位信号的响应。 IC 神经元亚群选择性地对自然呼叫回声对的频谱时间结构及其在动态声纳序列中的时间模式的组合做出反应。这些新发现表明，FM 蝙蝠对生物声纳信号参数的精细控制可能会调节 IC 神经元对回声延迟维度的选择性。新的和值得注意的回声定位蝙蝠执行精确的听觉时间计算来估计它们与物体的距离。在这里，我们报告说，调频蝙蝠下丘神经元对呼叫回声延迟或目标范围调整的响应选择性取决于自然回声定位序列中声音元素的时间模式和频谱时间特征。我们认为，对不同距离物体的回声响应是通过蝙蝠对其声纳发射的频谱时间模式的主动控制来控制的。
Echolocating bats must process temporal streams of sonar sounds to represent objects along the range axis. Neuronal echo-delay tuning, the putative mechanism of sonar ranging, has been characterized in the inferior colliculus (IC) of the mustached bat, an insectivorous species that produces echolocation calls consisting of constant frequency and frequency modulated (FM) components, but not in species that use FM signals alone. This raises questions about the mechanisms that give rise to echo-delay tuning in insectivorous bats that use different signal designs. To investigate whether stimulus context may account for species differences in echo-delay selectivity, we characterized single-unit responses in the IC of awake passively listening FM bats, Eptesicus fuscus, to broadcasts of natural sonar call-echo sequences, which contained dynamic changes in signal duration, interval, spectrotemporal structure, and echo-delay. In E. fuscus, neural selectivity to call-echo delay emerges in a population of IC neurons when stimulated with call-echo pairs presented at intervals mimicking those in a natural sonar sequence. To determine whether echo-delay selectivity also depends on the spectrotemporal features of individual sounds within natural sonar sequences, we studied responses to computer-generated echolocation signals that controlled for call interval, duration, bandwidth, sweep rate, and echo-delay. A subpopulation of IC neurons responded selectively to the combination of the spectrotemporal structure of natural call-echo pairs and their temporal patterning within a dynamic sonar sequence. These new findings suggest that the FM bat's fine control over biosonar signal parameters may modulate IC neuronal selectivity to the dimension of echo-delay.NEW & NOTEWORTHY Echolocating bats perform precise auditory temporal computations to estimate their distance to objects. Here, we report that response selectivity of neurons in the inferior colliculus of a frequency modulated bat to call-echo delay, or target range tuning, depends on the temporal patterning and spectrotemporal features of sound elements in a natural echolocation sequence. We suggest that echo responses to objects at different distances are gated by the bat's active control over the spectrotemporal patterning of its sonar emissions.