Auditory response properties in the superior paraolivary nucleus of the gerbil
Auditory response properties in the superior paraolivary nucleus of the gerbil
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DOI：
10.1152/jn.2002.87.6.2915
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发表时间：
2002-06-01
影响因子：
2.5
通讯作者：
Grothe, B
中科院分区：
文献类型：
--
作者：
Behrend, O;Brand, A;Grothe, B
上行听觉通路的特点是并行处理。在脑干水平，涉及几个已知具有不同明确功能的结构。然而，一个突出的脑干核，啮齿动物的上级橄榄旁核（SPN）和它的推定同源物在其他哺乳动物，背内侧橄榄周围核，功能是未知的。基于麻醉沙鼠的细胞外记录，我们测试了SPN在声音定位和时间加工中的作用。首先，双耳输入的存在表明SPN可能参与声音定位。虽然几乎一半的神经元表现出双耳的相互作用（其中大部分是从两侧兴奋），耳间的时间和强度差异（ITD; IID）的影响是微弱和模糊的。因此，SPN在声音定位中的直接功能似乎是不可信的。第二，输入章鱼和多极/星状细胞的耳蜗核和主细胞的内侧核的斜方体可能涉及到精确的时间处理的SPN。根据放电类型，观察到两个亚群的SPN细胞：约60%的神经元对纯音的持续放电，不规则的尖峰模式，没有锁相。只有四个神经元表现出规则的尖峰模式（“斩波”）。约40%的神经元的反应与相位ON或OFF放电。在具有持续放电的神经元中观察到的平均第一尖峰潜伏期显著短于ON应答者的平均第一尖峰潜伏期，但具有相当高的试验间变异（“抖动”）。ON应答者的亚群显示出小于+/-0.1 ms的抖动。大多数神经元（66%）对正弦幅度调制声音（SAM）做出持续响应，锁相至刺激包络。同样，ON应答者在锁相放电中表现出比持续应答者显著更高的时间精度。在基于尖峰速率的调制传递函数中观察到高变异性。在组织学上，证明了大量的甘氨酸能输入到SPN细胞的细胞化学标记物浓度。甘氨酸或其阻断剂的应用揭示了甘氨酸能抑制对SPN神经元听觉反应的深刻影响。至少两个亚群的神经元的存在与可以在形态学上区分的SPN细胞的不同子集一致。一个时间上不太精确的群体可能通过提供相当分散的抑制来调节其靶结构的加工。相比之下，精确的ON应答者可能向其靶点提供短的初始抑制脉冲。
The ascending auditory pathway is characterized by parallel processing. At the brain stem level, several structures are involved that are known to serve different well-defined functions. However, the function of one prominent brain stem nucleus, the rodent superior paraolivary nucleus (SPN) and its putative homologue in other mammals, the dorsomedial periolivary nucleus, is unknown. Based on extracellular recordings from anesthetized gerbils, we tested the role of the SPN in sound localization and temporal processing. First, the existence of binaural inputs indicates that the SPN might be involved in sound localization. Although almost half of the neurons exhibited binaural interactions (most of them excited from both sides), effects of interaural time and intensity differences (ITD; IID) were weak and ambiguous. Thus a straightforward function of SPN in sound localization appears to be implausible. Second, inputs from octopus and multipolar/stellate cells of the cochlear nucleus and from principal cells of the medial nucleus of the trapezoid body could relate to precise temporal processing in the SPN. Based on discharge types, two subpopulations of SPN cells were observed: about 60% of the neurons responded to pure tones with sustained discharges, with irregular spike patterns and no phase-locking. Only four neurons showed a regular spike pattern ("chopping"). About 40% of the neurons responded with phasic ON or OFF discharges. Average first spike latency observed in neurons with sustained discharges was significantly shorter than that of ON responders, but had a considerably higher trial-to-trial variation ("jitter"). A subpopulation of ON responders showed a jitter of less than +/-0.1 ms. Most neurons (66%) responded to sinusoidally amplitude-modulated sounds (SAM) with an ongoing response, phase-locked to the stimulus envelope. Again, ON responders showed a significantly higher temporal precision in the phase-locked discharge compared with the sustained responders. High variability was observed among spike-rate-based modulation transfer functions. Histologically, a massive concentration of cytochemical markers for glycinergic input to SPN cells was demonstrated. Application of glycine or its blockade revealed profound effects of glycinergic inhibition on the auditory responses of SPN neurons. The existence of at least two subpopulations of neurons is in line with different subsets of SPN cells that can be distinguished morphologically. One temporally less precise population might modulate the processing of its target structures by providing a rather diffuse inhibition. In contrast, precise ON responders might provide a short, initial inhibitory pulse to its targets.