Berson D M, Graybiel A M
Neuroscience. 1983 Jun;9(2):337-72. doi: 10.1016/0306-4522(83)90299-3.
The extrageniculate visual thalamus of the cat is divisible into several major subdivisions but only one receives dense fiber projections from the striate cortex. In the present study, modern axon transport techniques and acetylcholinesterase histochemistry were used to examine the internal organization of this striate-recipient zone and some of its afferent and efferent connections. A detailed study of the corticothalamic fiber projections of the striate cortex clarified the topographic organization and boundaries of the striate-recipient zone. The nature and course of "projection lines" within the zone were defined and the subdivision was shown to correspond closely to a region of relatively weak acetylcholinesterase staining. Corticothalamic projections from two regions of the extrastriate visual cortex, area 19 and the medial division of the Clare-Bishop complex, converge with those from area 17 in the striate-recipient zone, but these extrastriate areas have more widespread projections to the extrageniculate thalamus than does the striate cortex. A weak subcortical projection to the striate-recipient zone was demonstrated, apparently originating in the superior colliculus. Retrograde tracing experiments indicated that the corticothalamic inputs of the striate-recipient zone are precisely reciprocal by thalamocortical projections. Extrageniculate thalamic projections to area 17 arise exclusively from this thalamic subdivision and are highly topographically ordered. The striate-recipient zone projects massively and apparently retinotopically to area 19 and to the medial division of the Clarc-Bishop area, as well as area 21(a), but these extrastriate areas receive additional afferents from other subdivisions of the extrageniculate thalamus. These findings appear to rule out a "non-specific" functional role for the striate-recipient zone. In its topographic organization, its reciprocal connections with areas of the visual cortex, and its sheer volume, the zone seems comparable to the dorsal lateral geniculate nucleus and may be fairly considered a satellite of the geniculocortical system. Certain of the zone's organizational and connectional features may be clues to its functional role and its possible homologues in other mammalian forms.
猫的膝状体外视觉丘脑可分为几个主要亚区，但只有一个亚区接受来自纹状皮质的密集纤维投射。在本研究中，采用现代轴突运输技术和乙酰胆碱酯酶组织化学方法，研究了这个接受纹状皮质投射区域的内部组织结构及其一些传入和传出连接。对纹状皮质的皮质丘脑纤维投射进行的详细研究，明确了接受纹状皮质投射区域的拓扑组织和边界。确定了该区域内“投射线”的性质和走向，且该亚区与乙酰胆碱酯酶染色相对较弱的区域紧密对应。来自19区和克莱尔 - 毕晓普复合体内侧部这两个纹外视觉皮质区域的皮质丘脑投射，在接受纹状皮质投射区域与来自17区的投射汇聚，但这些纹外区域对膝状体外丘脑的投射比纹状皮质更广泛。已证实存在一条来自上丘、投射至接受纹状皮质投射区域的微弱皮质下通路。逆行追踪实验表明，接受纹状皮质投射区域的皮质丘脑输入与丘脑皮质投射精确地相互对应。膝状体外丘脑向17区的投射仅源于这个丘脑亚区，且具有高度的拓扑有序性。接受纹状皮质投射区域大量且明显按视网膜拓扑图方式投射至19区、克莱尔 - 毕晓普区域内侧部以及21(a)区，但这些纹外区域还接受来自膝状体外丘脑其他亚区的额外传入。这些发现似乎排除了接受纹状皮质投射区域具有“非特异性”功能作用的可能性。在其拓扑组织、与视觉皮质区域的相互连接以及其体积方面，该区域似乎与背侧外侧膝状核相当，可合理地被视为膝状体皮质系统的一个附属部分。该区域的某些组织和连接特征可能为其功能作用以及在其他哺乳动物中的可能同源物提供线索。
