Behan M
J Comp Neurol. 1984 Jun 1;225(4):591-604. doi: 10.1002/cne.902250409.
The electron microscopic autoradiographic method was used to identify terminals of axons from cortical areas 17, 18, and 19 in the superficial layers of the superior colliculus. The results show that terminals of area 17 neurons contain round vesicles and made asymmetrical synaptic contacts predominantly onto one or more dendrites or dendritic appendages. Some profiles postsynaptic to labeled terminals contain vesicles and presumably are involved in serial synaptic arrangements. Terminals of area 18 and 19 neurons in the superficial collicular layers appear to comprise two populations, one similar in most respects to area 17 terminals, containing round vesicles and making asymmetrical contacts. The other contains pleomorphic vesicles and makes symmetrical contacts upon dendrites and dendritic appendages. These terminals rarely contact more than one postsynaptic profile, and rarely do the postsynaptic profiles contain vesicles. The two populations of area 18 and 19 terminals containing round and pleomorphic vesicles, respectively, are present in the ratio of approximately 3:1, although this ratio varies throughout the sublaminae of the superficial collicular layers. The presence of two distinct types of cortical terminals in the colliculus suggests that cortical modulation of collicular processing is more complex than was previously conceived.
采用电子显微镜放射自显影法来识别上丘表层中来自17、18和19区皮质区域的轴突终末。结果显示，17区神经元的终末含有圆形囊泡，主要与一个或多个树突或树突附属物形成不对称突触联系。一些标记终末的突触后成分含有囊泡，推测参与了串联突触排列。上丘表层中18区和19区神经元的终末似乎包括两类，一类在大多数方面与17区终末相似，含有圆形囊泡并形成不对称联系。另一类含有多形性囊泡，与树突和树突附属物形成对称联系。这些终末很少与一个以上的突触后成分接触，突触后成分也很少含有囊泡。分别含有圆形和多形性囊泡的18区和19区两类终末，其比例约为3:1，尽管在整个上丘表层的亚层中这个比例有所变化。丘脑中存在两种不同类型的皮质终末，这表明皮质对丘脑加工的调制比之前所认为的更为复杂。
