Section of Neurobiology, Institute for Neuroscience, and Center for Perceptual Systems, The University of Texas at Austin, Austin, Texas 78712, USA.
J Neurosci. 2013 Apr 10;33(15):6367-79. doi: 10.1523/JNEUROSCI.5735-12.2013.
Neurons excited by stimulation of one ear and suppressed by the other, called excitatory/inhibitory (EI) neurons, are sensitive to interaural intensity disparities, the cues animals use to localize high frequencies. EI neurons are first formed in lateral superior olive, which then sends excitatory projections to the dorsal nucleus of the lateral lemniscus and the inferior colliculus (IC), both of which contain large populations of EI cells. We evaluate herein the inputs that innervate EI cells in the IC of Mexican free-tailed bats (Tadarida brasilensis mexicana) with in vivo whole-cell recordings from which we derived excitatory and inhibitory conductances. We show that the basic EI property in the majority of IC cells is inherited from lateral superior olive, but that each type of EI cell is also innervated by the ipsilateral or contralateral dorsal nucleus of the lateral lemniscus, as well as additional excitatory and inhibitory inputs from monaural nuclei. We identify three EI types, each of which receives a set of projections that is different from the other types. To evaluate the role that the various projections played in generating binaural responses, we used modeling to compute a predicted response from the conductances. We then omitted one of the conductances from the computation to evaluate the degree to which that input contributed to the binaural response. We show that the formation of the EI property in the various types is complex, and that some projections exert such subtle influences that they could not have been detected with extracellular recordings or even from intracellular recordings of postsynaptic potentials.
一侧耳刺激兴奋而另一侧耳抑制的神经元，称为兴奋/抑制（EI）神经元，对耳间强度差异敏感，这是动物用于定位高频声音的线索。EI 神经元最初在外侧上橄榄形成，然后向外侧丘系背核和下丘（IC）发出兴奋性投射，这两个核团都包含大量的 EI 细胞。我们通过活体全细胞记录评估了传入墨西哥自由长尾蝙蝠（Tadarida brasilensis mexicana）IC 中 EI 细胞的输入，从中我们得出了兴奋性和抑制性电导。我们表明，大多数 IC 细胞的基本 EI 特性是从外侧上橄榄遗传而来的，但每种 EI 细胞也受到同侧或对侧外侧丘系背核以及来自单耳核的额外兴奋性和抑制性输入的支配。我们鉴定出三种 EI 类型，每种类型都接收一组与其他类型不同的投射。为了评估各种投射在产生双耳反应中的作用，我们使用建模从电导计算预测的反应。然后，我们从计算中省略一个电导，以评估该输入对双耳反应的贡献程度。我们表明，各种类型 EI 特性的形成是复杂的，有些投射的影响如此微妙，以至于即使使用细胞外记录甚至是突触后电位的细胞内记录也无法检测到。
