FitzPatrick K A
J Comp Neurol. 1975 Nov 15;164(2):185-207. doi: 10.1002/cne.901640204.
The inferior colliculus of the squirrel monkey is made up of a large central nucleus, bordered by the smaller external and pericentral nuclei. The majority of cells in the central nucleus exhibit a pronounced laminar arrangement due to the orientation of their dendrites. In medial sections of the nucleus these laminae lie in a dorsorostral to ventrocaudal direction. More laterally the layers assume a horizontal orientation and at the far lateral edge of the central nucleus come to lie in a ventrorostral to dorsocaudal orientation. A single tonotopic representation of audible frequencies is present in the central nucleus. A regular progression of best frequencies from low to high is encountered as a microelectrode advances from dorsocaudal to ventrorostral in the sagittal plane. Penetrations in more medial regions of the central nucleus encounter neurons whose best frequencies represent a higher range of frequencies than those in the lateral parts. The orientation of the isofrequency laminae determined physiologically appears congruent with the orientation of the dendritic laminae. The relative volume of the central nucleus devoted to each octave from 250 Hz to 32 kHz was determined. Frequencies up to eight kHz command successively larger amounts of collicular tissue. The octave band from 8 to 16 kHz is represented by the greatest amount of collicular tissue. Disproportionate representation of frequency may be the consequence of innervation density along the basilar membrane.
松鼠猴的下丘由一个大的中央核组成，其周围是较小的外侧核和中央周核。由于中央核中大多数细胞的树突方向，这些细胞呈现出明显的分层排列。在核的内侧切片中，这些层呈背嘴侧到腹尾侧的方向。更靠外侧时，这些层呈水平方向，在中央核的最外侧边缘则呈腹嘴侧到背尾侧的方向。中央核中存在可听频率的单一音频定位表征。当微电极在矢状面从背尾侧推进到腹嘴侧时，会遇到最佳频率从低到高的规则变化。在中央核更内侧区域的穿透会遇到其最佳频率代表比外侧部分更高频率范围的神经元。生理上确定的等频率层的方向似乎与树突层的方向一致。确定了中央核中分配给从250赫兹到32千赫每个倍频程的相对体积。高达8千赫的频率依次占据越来越多的丘系组织。8至16千赫的倍频带由最大量的丘系组织代表。频率的不成比例表征可能是基底膜上神经支配密度的结果。
