Sanes D H, Goldstein N A, Ostad M, Hillman D E
Department of Otolaryngology, New York University School of Medicine, New York 10016.
J Comp Neurol. 1990 Apr 15;294(3):443-54. doi: 10.1002/cne.902940312.
We have investigated the morphology of dendritic arbors in a central auditory nucleus, the lateral superior olive, of the Mongolian gerbil. Morphometric observations were obtained directly from Golgi-impregnated material by using a microcomputer-based three-dimensional data acquisition system. In particular, measurements were made to determine the dendritic arborization across each of three axes: the tonotopic axis, the rostrocaudal axis, and the isofrequency axis (i.e., perpendicular to the tonotopic axis). The tonotopic position of each cell was computed on the basis of a topographic map that has been constructed for the gerbil LSO (Sanes et al.: J. Comp. Neurol. 279:436-444, 1989). It was found that the span of a dendritic arbor along the tonotopic axis was directly correlated with the neuron's tonotopic position: Low frequency neurons had much broader arborizations than high frequency neurons. Moreover, the distribution of frequency bandwidths to which single LSO neurons responded showed a striking similarity to dendritic arborizations across the tonotopic axis. Lower frequency neurons responded to a larger number of octaves than higher frequency neurons. There was no correlation between tonotopic position and dendritic arborization in the isofrequency or rostrocaudal axis. Nor was there any correlation between frequency and total dendritic length, number of primary dendrites, or soma area. However, there was a small but significant difference between the primary dendrite diameter of low and high frequency neurons. Low frequency neurons had significantly greater diameters. These results suggest that the frequency selectivity of central auditory neurons may employ, as one morphological substrate, the distance over which their dendrites arborize along the tonotopic axis.
我们研究了蒙古沙鼠中枢听觉核团——外侧上橄榄核中树突分支的形态。通过基于微机的三维数据采集系统，直接从高尔基染色的材料中获取形态测量数据。具体而言，进行测量以确定树突分支在三个轴向上的情况：音频拓扑轴、前后轴以及等频轴（即垂直于音频拓扑轴）。每个细胞的音频拓扑位置是根据已构建的沙鼠外侧上橄榄核地形图计算得出的（Sanes等人：《比较神经学杂志》279:436 - 444，1989年）。结果发现，树突分支沿音频拓扑轴的跨度与神经元的音频拓扑位置直接相关：低频神经元的树突分支比高频神经元的要宽得多。此外，单个外侧上橄榄核神经元所响应的频率带宽分布与沿音频拓扑轴的树突分支情况显示出惊人的相似性。低频神经元比高频神经元能响应更多倍频程。在等频轴或前后轴上，音频拓扑位置与树突分支之间没有相关性。频率与树突总长度、初级树突数量或胞体面积之间也没有相关性。然而，低频和高频神经元的初级树突直径存在微小但显著的差异。低频神经元的直径明显更大。这些结果表明，中枢听觉神经元的频率选择性可能利用其树突沿音频拓扑轴分支的距离作为一种形态学基础。
