| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2001: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
Memory signals processed in the hippocampal formation are propagated to the entorhinal cortex by way of several efferent cortical pathways. In this research project (1999-2001), we studied the morphological characteristics of projections of these pathways and associative connections in the cortical areas by using anterograde and retrograde tract tracing methods in the rat.
Cells projecting to the medial and lateral entorhinal cortices (MEA, LEA), the retrosplenial granular cortex (RSG), the parasubiculum (PARA) and the presubiculum (PRE) were consistently observed throughout the entire septotemporal extent of the subiculum. The septal subiculum projected to the septal parts of RSG, PARA and PRE, and to the lateral part of MEA and LEA (close to the rhinal fissure), while the temporal subiculum projected to the opposite sides of the areas. In the transverse plane, these projection cells were located in the superficial four-fifths of the subicular pyramidal cell layer, but few in the deepest portion of the layer. These cortical projection cells seemed to be belonged to the subcortical projection cells to the medial mammillary body, the hypothalamic area and the nucleus accumbens.
Common to these cortical pathways, the fibers from a certain septotemporal level of the subiculum are terminated in a zonal area in the entorhinal cortex. The terminal zones are expanded rostrocaudally while restricted mediolaterally in the MEA and LEA, and thus they are arranged parallel to the rhinal sulcus. In this research project it has been elucidated that there is a consistent topography in the projections from subiculum to MEA, LEA, PRE, PARA and RSG, and also that there are longitudinal associational connections in the subiculum and PRE.
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