Lyon David C, Jain Neeraj, Kaas Jon H
Department of Psychology, Vanderbilt University, 301 Wilson Hall, Nashville, Tennessee 37203, USA.
J Comp Neurol. 2003 Dec 22;467(4):607-27. doi: 10.1002/cne.10940.
Patterns of thalamocortical connections were related to architectonically defined subdivisions of the pulvinar complex and the dorsolateral geniculate nucleus (LGN) in tree shrews (Tupaia belangeri). Tree shrews are of special interest because they are considered close relatives of primates, and they have a highly developed visual system. Several distinguishable tracers were injected within and across cortical visual areas in individual tree shrews in order to reveal retinotopic patterns and cortical targets of subdivisions of the pulvinar. The results indicate that each of the three architectonic regions of the pulvinar has a distinctive pattern of cortical connections and that one of these divisions is further divided into two regions with different patterns of connections. Two of the pulvinar nuclei have similar retinotopic patterns of projections to caudal visual cortex. The large central nucleus of the pulvinar (Pc) projects to the first and second visual areas, V1 and V2, and an adjoining temporal dorsal area (TD) in retinotopic patterns indicating that the upper visual quadrant is represented dorsal to the lower quadrant in Pc. The smaller ventral nucleus (Pv) which stains darkly for the Cat-301 antigen, projects to these same cortical areas, with a retinotopic pattern. Pv also projects to a temporal anterior area, TA. The dorsal nucleus (Pd), which densely expresses AChE, projects to posterior and ventral areas of temporal extrastriate cortex, areas TP and TPI. A posterior nucleus, Pp, projects to anterior areas TAL and TI, of the temporal lobe, as well as TPI. Injections in different cortical areas as much as 6 mm apart labeled overlapping zones in Pp and double-labeled some cells. These results indicate that the visual pulvinar of tree shrews contains at least four functionally distinct subdivisions, or nuclei. In addition, the cortical injections revealed that the LGN projects topographically and densely to V1 and that a significant number of LGN neurons project to V2 and TD.
丘脑皮质连接模式与树鼩(Tupaia belangeri)中枕核复合体和背外侧膝状核(LGN)在结构上定义的亚区相关。树鼩具有特殊的研究意义,因为它们被认为是灵长类动物的近亲,并且拥有高度发达的视觉系统。为了揭示枕核亚区的视网膜拓扑模式和皮质靶点,在个体树鼩的皮质视觉区域内及跨区域注射了几种可区分的示踪剂。结果表明,枕核的三个结构区域各自具有独特的皮质连接模式,其中一个分区进一步分为两个具有不同连接模式的区域。两个枕核具有相似的向尾侧视觉皮质投射的视网膜拓扑模式。枕核的大中央核(Pc)以视网膜拓扑模式投射到第一和第二视觉区V1和V2,以及相邻的颞背区(TD),这表明在Pc中,上视觉象限在视网膜拓扑上位于下视觉象限的背侧。对Cat-301抗原染色较深的较小腹侧核(Pv)也以视网膜拓扑模式投射到这些相同的皮质区域。Pv还投射到颞前区TA。密集表达乙酰胆碱酯酶(AChE)的背侧核(Pd)投射到颞叶纹外皮质的后部和腹侧区域,即TP和TPI区。后核Pp投射到颞叶的前区TAL和TI,以及TPI区。在相距多达6毫米的不同皮质区域进行注射,标记了Pp中的重叠区域,并使一些细胞出现双重标记。这些结果表明,树鼩的视觉枕核至少包含四个功能上不同的亚区或核。此外,皮质注射显示,LGN以拓扑方式密集投射到V1,并且大量LGN神经元投射到V2和TD。