Lee Norman, Schrode Katrina M, Bee Mark A
Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, 55108, USA.
Biology Department, St. Olaf College, Northfield, MN, 55057, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2017 Sep;203(9):749-772. doi: 10.1007/s00359-017-1195-3. Epub 2017 Jul 26.
Diverse animals communicate using multicomponent signals. How a receiver's central nervous system integrates multiple signal components remains largely unknown. We investigated how female green treefrogs (Hyla cinerea) integrate the multiple spectral components present in male advertisement calls. Typical calls have a bimodal spectrum consisting of formant-like low-frequency (0.9 kHz) and high-frequency (2.7 kHz) components that are transduced by different sensory organs in the inner ear. In behavioral experiments, only bimodal calls reliably elicited phonotaxis in no-choice tests, and they were selectively chosen over unimodal calls in two-alternative choice tests. Single neurons in the inferior colliculus of awake, passively listening subjects were classified as combination-insensitive units (27.9%) or combination-sensitive units (72.1%) based on patterns of relative responses to the same bimodal and unimodal calls. Combination-insensitive units responded similarly to the bimodal call and one or both unimodal calls. In contrast, combination-sensitive units exhibited both linear responses (i.e., linear summation) and, more commonly, nonlinear responses (e.g., facilitation, compressive summation, or suppression) to the spectral combination in the bimodal call. These results are consistent with the hypothesis that nonlinearities play potentially critical roles in spectral integration and in the neural processing of multicomponent communication signals.
多种动物利用多组分信号进行交流。然而，接收者的中枢神经系统如何整合多个信号组分在很大程度上仍不为人知。我们研究了雌性绿树蛙（Hyla cinerea）如何整合雄性求偶鸣叫中存在的多个频谱组分。典型的鸣叫具有双峰频谱，由类似共振峰的低频（约0.9千赫）和高频（约2.7千赫）组分组成，这些组分由内耳中的不同感觉器官传导。在行为实验中，只有双峰鸣叫在无选择测试中可靠地引发了趋声行为，并且在双选测试中，它们被选择性地优先于单峰鸣叫。根据清醒的、被动聆听的实验对象在下丘中的单个神经元对相同双峰和单峰鸣叫的相对反应模式，将其分类为组合不敏感单元（27.9%）或组合敏感单元（72.1%）。组合不敏感单元对双峰鸣叫和一个或两个单峰鸣叫的反应相似。相比之下，组合敏感单元对双峰鸣叫中的频谱组合既表现出线性反应（即线性叠加），更常见的是表现出非线性反应（例如易化、压缩叠加或抑制）。这些结果与以下假设一致，即非线性在频谱整合和多组分通信信号的神经处理中可能起着关键作用。
