Henkel C K, Shneiderman A
Department of Anatomy, Bowman Gray School of Medicine, Winston-Salem, North Carolina 27103.
J Comp Neurol. 1988 May 22;271(4):577-88. doi: 10.1002/cne.902710408.
The nucleus sagulum, an area of the midbrain tegmentum, has been considered a component of a lateral tegmental system within the ascending auditory pathway to the thalamus. In this study, connections of the nucleus sagulum within the midbrain were investigated in adult cats. Tracing methods using anterograde and retrograde axonal transport of markers were employed. The nucleus sagulum was identified as a region of principally small neurons (261 +/- 79 micron2) at the margin of the midbrain and neighboring the nuclei of the lateral lemniscus. Injections of tritiated leucine in the nucleus sagulum labeled axons that ended in dense patches within the superficial layers of the caudal portion of the dorsal cortex of the inferior colliculus on the ipsilateral side. Retrograde experiments confirmed this connection. Other axonal projections labeled in the anterograde studies included fibers ending in the dorsomedial nucleus, the superficial layers of the dorsal cortex, and the rostral nucleus of the inferior colliculus with some bilateral distribution. Outside of the inferior colliculus, sagulum injections labeled other axons ending in the ventral intercollicular tegmentum on both sides and in a dorsal and rostral region of the contralateral nucleus sagulum that appeared contiguous with the dorsal nucleus of the lateral lemniscus. The latter region included a population of larger neurons (340-540 micron2) and had different connections with the inferior colliculus. The distribution of axonal labeling after injections in the nucleus sagulum was contrasted with the distribution of projections from several neighboring areas of the lateral tegmentum, including the dorsal nucleus of the lateral lemniscus. None of these areas exhibited connections with the superficial layers of the caudal cortex of the inferior colliculus, which was the major target in the inferior colliculus of the nucleus sagulum. Thus, the results indicated that the nucleus sagulum is distinguished from adjacent regions of the lateral tegmentum by its connectivity. Its association with midbrain auditory pathways is supported by these connections as well as ascending ones to the auditory thalamus.
中脑被盖区的核袋，被认为是丘脑听觉上行通路中外侧被盖系统的一个组成部分。在本研究中，对成年猫中脑内核袋的连接进行了研究。采用了利用标记物的顺行和逆行轴突运输的追踪方法。核袋被确定为中脑边缘主要由小神经元（261±79平方微米）组成的区域，与外侧丘系核相邻。在核袋中注射氚标记的亮氨酸标记了轴突，这些轴突在同侧下丘背侧皮质尾部的表层内形成密集斑块。逆行实验证实了这种连接。顺行研究中标记的其他轴突投射包括终止于背内侧核、背侧皮质表层和下丘嘴侧核的纤维，有一些双侧分布。在下丘之外，向核袋注射标记了其他终止于双侧腹侧下丘间被盖以及对侧核袋背侧和嘴侧区域的轴突，该区域似乎与外侧丘系背核相邻。后一区域包括一群较大的神经元（340 - 540平方微米），与下丘有不同的连接。在核袋注射后轴突标记的分布与外侧被盖几个相邻区域的投射分布形成对比，包括外侧丘系背核。这些区域均未表现出与下丘尾侧皮质表层的连接，而下丘尾侧皮质表层是核袋在下丘的主要靶区。因此，结果表明核袋通过其连接性与外侧被盖的相邻区域相区别。这些连接以及通向听觉丘脑的上行连接支持了它与中脑听觉通路的关联。
