Doucet J R, Ryugo D K
Center for Hearing Sciences, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
J Comp Neurol. 1997 Aug 25;385(2):245-64.
Local circuit interactions between the dorsal and ventral divisions of the cochlear nucleus are known to influence the evoked responses of the resident neurons to sound. In the present study, we examined the projections of neurons in the ventral cochlear nucleus to the dorsal cochlear nucleus by using retrograde transport of biotinylated dextran amine injected into restricted but different regions of the dorsal cochlear nucleus. In all cases, we found retrogradely labeled granule, unipolar brush, and chestnut cells in the granule cell domain, and retrogradely labeled multipolar cells in the magnocellular core of the ventral cochlear nucleus. A small number of the labeled multipolar cells were found along the margins of the ventral cochlear nucleus, usually near the boundaries of the granule cell domain. Spherical bushy, globular bushy, and octopus cells were not labeled. Retrogradely-labeled auditory nerve fibers and the majority of labeled multipolar neurons formed a narrow sheet extending across the medial-to-lateral extent of the ventral cochlear nucleus whose dorsoventral position was topographically related to the injection site. Labeled multipolar cells within the core of the ventral cochlear nucleus could be divided into at least two distinct groups. Planar neurons were most numerous, their somata found within the associated band of labeled fibers, and their dendrites oriented within this band. This arrangement mimics the organization of isofrequency contours and implies that planar neurons respond best to a narrow range of frequencies. In contrast, radiate neurons were infrequent, found scattered throughout the ventral cochlear nucleus, and had long dendrites oriented perpendicular to the isofrequency contours. This dendritic orientation suggests that radiate neurons are sensitive to a broad range of frequencies. These structural differences between planar and radiate neurons suggest that they subserve separate functions in acoustic processing.
已知耳蜗核背侧和腹侧分区之间的局部回路相互作用会影响驻留神经元对声音的诱发反应。在本研究中，我们通过将生物素化葡聚糖胺逆行运输到耳蜗核背侧受限但不同的区域，研究了耳蜗腹侧核神经元向耳蜗背侧核的投射。在所有情况下，我们在颗粒细胞区域发现了逆行标记的颗粒细胞、单极刷状细胞和栗色细胞，在耳蜗腹侧核的大细胞核心中发现了逆行标记的多极细胞。在耳蜗腹侧核的边缘发现了少量标记的多极细胞，通常靠近颗粒细胞区域的边界。球形布什细胞、球状布什细胞和章鱼细胞未被标记。逆行标记的听神经纤维和大多数标记的多极神经元形成了一个狭窄的薄片，横跨耳蜗腹侧核的内侧到外侧范围，其背腹位置与注射部位存在拓扑关系。耳蜗腹侧核核心内的标记多极细胞可分为至少两个不同的组。平面神经元数量最多，其胞体位于相关的标记纤维带内，其树突也在此带内定向。这种排列模仿了等频率轮廓的组织方式，意味着平面神经元对窄频率范围反应最佳。相比之下，辐射状神经元较少见，分散在整个耳蜗腹侧核中，其长树突垂直于等频率轮廓定向。这种树突方向表明辐射状神经元对广泛的频率敏感。平面神经元和辐射状神经元之间的这些结构差异表明它们在听觉处理中发挥着不同的功能。
