Biomedical Engineering Department, Boston University, Boston, Massachusetts;
J Neurophysiol. 2014 Jan;111(1):164-81. doi: 10.1152/jn.00450.2013. Epub 2013 Oct 23.
Human listeners are sensitive to interaural time differences (ITDs) in the envelopes of sounds, which can serve as a cue for sound localization. Many high-frequency neurons in the mammalian inferior colliculus (IC) are sensitive to envelope-ITDs of sinusoidally amplitude-modulated (SAM) sounds. Typically, envelope-ITD-sensitive IC neurons exhibit either peak-type sensitivity, discharging maximally at the same delay across frequencies, or trough-type sensitivity, discharging minimally at the same delay across frequencies, consistent with responses observed at the primary site of binaural interaction in the medial and lateral superior olives (MSO and LSO), respectively. However, some high-frequency IC neurons exhibit dual types of envelope-ITD sensitivity in their responses to SAM tones, that is, they exhibit peak-type sensitivity at some modulation frequencies and trough-type sensitivity at other frequencies. Here we show that high-frequency IC neurons in the unanesthetized rabbit can also exhibit dual types of envelope-ITD sensitivity in their responses to SAM noise. Such complex responses to SAM stimuli could be achieved by convergent inputs from MSO and LSO onto single IC neurons. We test this hypothesis by implementing a physiologically explicit, computational model of the binaural pathway. Specifically, we examined envelope-ITD sensitivity of a simple model IC neuron that receives convergent inputs from MSO and LSO model neurons. We show that dual envelope-ITD sensitivity emerges in the IC when convergent MSO and LSO inputs are differentially tuned for modulation frequency.
人类听众对声音包络的耳间时间差(ITD)敏感,这可以作为声音定位的线索。哺乳动物下丘中的许多高频神经元对正弦幅度调制(SAM)声音的包络 ITD 敏感。通常,包络 ITD 敏感的 IC 神经元表现出峰型敏感性或谷型敏感性,分别在相同的延迟处跨频率最大放电或最小放电,与在中侧上橄榄核(MSO 和 LSO)的双耳相互作用的主要部位观察到的反应一致。然而,一些高频 IC 神经元在其对 SAM 音调的反应中表现出双重类型的包络 ITD 敏感性,即在某些调制频率下表现出峰型敏感性,而在其他频率下表现出谷型敏感性。在这里,我们表明,未麻醉的兔的高频 IC 神经元也可以在其对 SAM 噪声的反应中表现出双重类型的包络 ITD 敏感性。这种对 SAM 刺激的复杂反应可能是由 MSO 和 LSO 对单个 IC 神经元的会聚输入实现的。我们通过实现双耳通路的生理显式计算模型来检验这一假设。具体来说,我们检查了一个简单的模型 IC 神经元的包络 ITD 敏感性,该神经元接收来自 MSO 和 LSO 模型神经元的会聚输入。我们表明,当会聚的 MSO 和 LSO 输入对调制频率进行差异调谐时,IC 中会出现双重包络 ITD 敏感性。
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