Brown M C, Pierce S, Berglund A M
Department of Physiology, Harvard Medical School, Boston 02115.
J Comp Neurol. 1991 Jan 8;303(2):300-15. doi: 10.1002/cne.903030211.
Olivocochlear neurons have somata in the superior olivary complex and provide an efferent innervation to the cochlea. One subgroup of olivocochlear neurons, medial olivocochlear neurons, sends fibers to innervate the cochlear outer hair cells. En route to the cochlea, medial olivocochlear fibers give off branches to the ventral cochlear nucleus, the first auditory center of the brain. This study examines the cochlear-nucleus branches of medial olivocochlear fibers, comparing those from fibers that innervate the cochlear base with those from fibers that innervate the cochlear apex. Basal fibers give off dorsal branches to the granule cell lamina and ventral branches to the auditory nerve root. Apical fibers give off few dorsal branches but many ventral branches that terminate rostrally to the nerve root. This cochleotopic mapping of medial olivocochlear branches corresponds in a general way to that of afferent fibers. Unlike afferent fibers, however, the branches terminate primarily along the edges of the cochlear nucleus. In the mouse, the particular edges of termination are (1) the medial border of the ventral cochlear nucleus where it meets the underlying vestibular nerve root, and (2) the border between the ventral cochlear nucleus and the granule cell lamina. Neurons and dendrites of these border regions may thus integrate efferent and afferent information in a frequency-specific manner.
橄榄耳蜗神经元的胞体位于上橄榄复合体，为耳蜗提供传出神经支配。橄榄耳蜗神经元的一个亚群，即内侧橄榄耳蜗神经元，发出纤维支配耳蜗外毛细胞。在内侧橄榄耳蜗纤维到达耳蜗的途中，它们会向腹侧耳蜗核发出分支，腹侧耳蜗核是大脑的第一个听觉中枢。本研究考察了内侧橄榄耳蜗纤维的耳蜗核分支，比较了支配耳蜗基部的纤维分支和支配耳蜗顶部的纤维分支。基部纤维向颗粒细胞层发出背侧分支，向听神经根发出腹侧分支。顶部纤维发出的背侧分支很少，但有许多腹侧分支，这些腹侧分支在神经根的前方终止。内侧橄榄耳蜗分支的这种耳蜗拓扑映射在总体上与传入纤维的映射相对应。然而，与传入纤维不同的是，这些分支主要沿着耳蜗核的边缘终止。在小鼠中，终止的特定边缘是：（1）腹侧耳蜗核与下方前庭神经根相接处的内侧边缘，以及（2）腹侧耳蜗核与颗粒细胞层之间的边界。因此，这些边界区域的神经元和树突可能以频率特异性的方式整合传出和传入信息。
