| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1995: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1994: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
The present data revealed dense striate projections to PMLS and to caudal most aspect of PLLS and moderate to weak projections to AMLS/PLLS.No projection to ALLS was observed. Visually responsive along the anterior ectosylvian sulcus maintains dense interconnections ALLS/PLLS.LS is the predominate source of extrastriate visual projections to the striatum. Because striatal activity is known to modulate the activity of deep laminae output neurons in SC by way of double inhibitory GABA-ergic connections through the pars reticulata of the substantia nigra (SNr), it has been suggested that cortically-processed visual information from LS can not only influence neurons in the deep laminae of superior colliculusdirectly via corticotectal projections but also indirectly via the basal ganglia.
The present results indicated that all LS regions project to various regions of the pretectal nuclei as well as all nuclei of the accessory optic system. These unclei have been known as an important visuo-m
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otor relay between the retina and pre-oculomotor structures. Furthermore, the present results on the corticotectal projections from LS confirmed those of previous studies.
In the present study, the labeled axons and terminals from a single, focal injection of biocytin could be observed rostrocaudally within each bank up to rather long distance (8-10 mm) from injection site. This distance is considerably long intracortical connections, suggesting that the considerable intrinsic connectivity within LS serves not only to link subregions within a given region but across regions as well. Furthermore, following medial bank injections, a number of labeled axons and terminals were distributed in the lateral bank, while very few label could be detected in the medial bank after lateral bank injections. On the other hand, the rostralmost of ALLS-AMLS and the caudalmost of PLLS-PMLS have moderate reciprocal interconnections. Thus, the main stream of information within LS tends to be the mediolateral direction. In the present biocytin experiments, the laminar distribution of intra-areal projection exhibited a similar pattern which was independent of the rostrocaudal as well as mediolateral position of the injection site. Thus, these terminal labelings were distributed in both supra-and infragranular layrs. Furthermore, our WGA-HRP experiments indicated that ALLS,PLLS,AMLS,PMLS,and fundus all receive intra-areal afferent projections from both the supragranular and infragranular cortical layrs. Using a number of hierarchical criteria as described above, the interconnections among LS subregions seems to be no clear hierachial relationship among subregions of LS or may have feed-forward and feed-back pathways. Less
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