Introduction to the superior olivary complex
Introduction to the superior olivary complex
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DOI：
10.1002/1097-0029(20001115)51:4
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发表时间：
2000-11
影响因子：
2.5
通讯作者：
S. Reuss
中科院分区：
文献类型：
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作者：
S. Reuss
上橄榄复合体（SOC）是一组相互关联的核，位于基底脑干两侧，是哺乳动物中枢听觉系统的一部分，由多个神经位点组成，通过多条平行通路相互连接，其中许多投射是局部组织的。SOC的功能包括通过上行听觉通路处理耳蜗信号，检测耳间声强和时间差作为空间映射的基础，以及对耳蜗机制的反馈控制（see Moore, 1994; Tsuchitani and Johnson, 1991; Warr, 1992）。虽然SOC也参与非听觉功能，并且一些听觉信息绕过SOC，但毫无疑问，SOC在听觉过程中起着举足轻重的作用。广泛的技术被用来揭示这些功能，从单单元电生理学到听觉脑干反应的记录，从组织化学到原位杂交，从神经元追踪到损伤和听力创伤的产生。在当前的《显微镜研究与技术》中，几个研究SOC的小组调查了他们的结果，并强调了该领域的最新进展。负责声音感知的细胞是耳蜗Corti器官的内毛细胞和外毛细胞（IHC， OHC）。它们平行于耳蜗管的纵轴排列。这两种感觉细胞都由螺旋神经节神经元的传入树突连接。因此，毛细胞信息被传递到螺旋轴突终止的耳蜗核（CN）复合体。它们的分支在前、后腹侧和中枢背侧形成突触接触。两侧的CN投射到SOC， SOC由三个主要核组成，即外侧和内侧橄榄上核（LSO， MSO）和梯形体内侧核（MNTB）以及一些不太明确的橄榄周神经元群。图1所示为豚鼠脑干SOC的位置。对许多哺乳动物SOC的比较研究表明，不同物种之间在核的形态、范围和功能上存在相当大的差异（详见Schwartz， 1992）。例如，耳周群，特别是MSO（通常与耳间时差处理有关）在人类SOC中很突出（见Moore等人，1999;Moore，第403-412页）。上榄核复合体通过外侧小丘将上行轴突发送到外侧小丘核（NLL）和下丘分支（IC），后者是听觉上行通路几乎所有部分的目标（概述见Aitkin, 1989; Webster, 1995）。先前已经回顾了上升突起的解剖模式和作用（Helfert et al., 1991）。有证据表明，同侧MSO和对侧LSO向IC中央核的投射是兴奋性的，而来自同侧LSO的投射是抑制性的（Oliver等，1995）。SOC信息与来自CN和NLL的信息相结合以调节IC加工的模式对听力和声音定位等听觉功能具有重要意义。奥利弗在本期（355-363页）中讨论了所涉及的路线及其功能角色。然后，主上升通路将IC连接到内侧膝状体（MGB），并依次连接到初级听觉皮层复合体。在人脑中，听觉皮层位于Heschl的横回（Brodmann的41区和42区）。除了其上升投射外，SOC也表现出指向耳蜗的下降投射。SOC神经元的轴突形成所谓的耳蜗束（Papez, 1930; Rasmussen, 1946），与OHC或IHC底部螺旋神经节细胞传入过程的突触直接形成突触。在大鼠中，主要的同侧投射源于侧侧SOC中具有极性树突的小神经元。另一组位于内侧SOC，由较大的多极神经元组成，主要投射到对侧耳蜗（White and Warr, 1983）。下行听觉系统的组织，特别是耳蜗-耳蜗投影的组织，已经有了比较详细的描述（Spangler和Warr, 1991; Warr, 1992）。本期提到了最近发现的关于下降投影的一些方面（Reuss和Riemann， 318-329页；Robertson和Mulders， 307-317页）。此外，有证据表明，存在一个小的，第三组神经元提供上升和下降的投射。这是在向IC和同侧耳蜗注射不同示踪物质后的双逆行神经元示踪中发现的（Reuss等，1999；Riemann和Reuss， 1998）。在SOC神经元中发现的神经活性物质包括乙酰胆碱、氨基酸递质如谷氨酸（Moore and Moore, 1987）、甘氨酸（Bledsoe et al., 1990）、GABA （Wynne et al., 1995）和各种神经活性肽。在传入纤维中检测到胆囊收缩素、生长抑素、P物质和脑啡肽（血清素和去甲肾上腺素也是如此）。它们的来源和可能的功能角色已经在前面进行了回顾（Caspary和Finlayson, 1991; Wenthold, 1991），在这里进行了讨论（Robertson和Mulders，本期，307-317页）。神经元中发现了降钙素基因相关肽、脑啡肽和肌啡肽，它们可能在SOC神经元中共存（Safieddine和Eybalin， 1992）。其中一些细胞与耳蜗突起有关，耳蜗突起包括内侧和外侧系统（MOC， LOC）。它们具有多种功能，包括频率选择性，增加信噪比和保护耳蜗免受声音损伤，可能是通过利用OHC的收缩反应抑制耳蜗敏感性（见Warr， 1992）。神经显微镜研究与技术51:303-306 （2000）
The superior olivary complex (SOC), a group of interrelated nuclei bilaterally located in the basal brainstem, is part of the mammalian central auditory system consisting of various neural sites connected to each other by multiple parallel pathways in which many projections are tonotopically organized. The functions of the SOC include the processing of cochlear signals via the ascending auditory pathway, the detection of interaural sound intensity and time differences as the basis of spatial mapping, as well as feedback control of cochlear mechanisms (see Moore, 1994; Tsuchitani and Johnson, 1991; Warr, 1992). Although the SOC is also involved in non-auditory functions, and some auditory information bypasses the SOC, there is no doubt that it plays a pivotal role in hearing processes. A wide range of techniques have been employed to unveil these functions, ranging from single-unit electrophysiology to recording of the auditory brainstem response, from histochemistry to in situ hybridization, and from neuronal tracing to lesions and the production of hearing traumata. In the present volume of Microscopy Research and Technique, several groups investigating the SOC survey their results and highlight recent advances in the field. The cells responsible for the perception of sound are the inner and outer hair cells (IHC, OHC) of the organ of Corti in the cochlea. They are arranged parallel to the longitudinal axis of the cochlear duct. Both types of sensory cells are contacted by afferent dendrites from spiral ganglion neurons. Hair cell information is, thus, transmitted to the cochlear nucleus (CN) complex where spiral axons terminate. They branch to make synaptic contacts in the anterior and posterior ventral and in the dorsal CN. The CN of both sides project to the SOC, which is composed of three principal nuclei, i.e., the lateral and medial superior olivary nuclei (LSO, MSO) and the medial nucleus of the trapezoid body (MNTB) and of some less-defined periolivary neuronal groups. The location of the SOC in the guinea pig brainstem is shown in Figure 1. The comparative study of the SOC in many mammals revealed that considerable differences between species exist in morphology, extent, and function of the nuclei (for review see Schwartz, 1992). For example, the periolivary groups and, in particular, the MSO (usually associated with processing of interaural time differences) are prominent in the human SOC (see Moore et al., 1999; Moore, pages 403–412 this issue). The superior olivary complex sends, via the lateral lemniscus, ascending axons to the nuclei of the lateral lemniscus (NLL) and to the subdivisions of the inferior colliculus (IC), the target of virtually all parts of the ascending auditory pathway (for overviews see Aitkin, 1989; Webster, 1995). The anatomical patterns and roles of the ascending projections have been reviewed previously (Helfert et al., 1991). There is evidence that the ipsilateral MSO and contralateral LSO projections to the central nucleus of the IC are excitatory, while those from the ipsilateral LSO are inhibitory (Oliver et al., 1995). The modes through which SOC information is integrated with those from CN and NLL to regulate processing in the IC are important for auditory functions such as hearing and sound localization. The routes involved and their functional roles are discussed by Oliver in this issue (pages 355–363). The major ascending pathway then connects the IC to the medial geniculate body (MGB) and, in turn, with the primary auditory cortical complex. In the human brain, the auditory cortex is located in the transverse gyri of Heschl (areas 41 and 42 of Brodmann). In addition to its ascending projections, the SOC also exhibits a descending projection directed to the cochlea. Axons of SOC neurons build the so-called olivo-cochlear bundle (Papez, 1930; Rasmussen, 1946) and make direct synapses with OHC or synapse at afferent processes of spiral ganglion cells at the base of IHC. In the rat, a predominantly ipsilateral projection stems from small neurons with polar dendrites in the lateral SOC. The other group is located in the medial SOC and consists of larger multipolar neurons that project mainly to the contralateral cochlea (White and Warr, 1983). The organization of the descending auditory systems and, in particular, of olivo-cochlear projections have been comparatively described in detail (Spangler and Warr, 1991; Warr, 1992). Some recently discovered aspects of the descending projections are mentioned in this issue (Reuss and Riemann, pages 318–329; Robertson and Mulders, pages 307–317). In addition, there is evidence that a small, third group of neurons exists that provides both ascending and descending projections. This was found upon double retrograde neuronal tracing following injection of different tracer substances into the IC and the ipsilateral cochlea (Reuss et al., 1999; Riemann and Reuss, 1998). The neuroactive substances found in SOC neurons include acetylcholine, amino acid transmitters such as glutamate (Moore and Moore, 1987), glycine (Bledsoe et al., 1990), GABA (Wynne et al., 1995), and various neuroactive peptides. Cholecystokinin, somatostatin, substance P, and enkephalins were detected in afferent fibers (which is also the case for serotonin and noradrenaline). Their sources and possible functional roles were reviewed previously (Caspary and Finlayson, 1991; Wenthold, 1991) and are discussed here (Robertson and Mulders, this issue, pages 307–317). Found in neurons were calcitonin gene-related peptide, enkephalins and dynorphins, which may co-exist in SOC neurons (Safieddine and Eybalin, 1992). Some of these cells were related to the olivo-cochlear projections that comprise medial and lateral systems (MOC, LOC). They have various functions including frequency selectivity, augmentation of signal-to-noise ratio and protection of the cochlea from sound damage, probably by suppressing cochlear sensitivity utilizing contractile responses of OHC (see Warr, 1992). The set of neuroMICROSCOPY RESEARCH AND TECHNIQUE 51:303–306 (2000)