Neuroscience
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The projections of the subiculum, as the main output structure of the hippocampal formation, to the striatum were studied in the rat using the anterograde tracer Phaseolus vulgaris leucoagglutinin. It appears that not only the entire nucleus accumbens, part of the so-called ventral striatum, receives fibres from the subiculum, but that the hippocampal projection area in the striatum includes also the most medial, ventral, rostral and caudal parts of the caudate-putamen complex. Moreover, a relatively small number of fibres and terminals are present in the striatal elements of the medial part of the olfactory tubercle. ⋯ Very sparse projections are found to the contralateral nucleus accumbens, arranged in a topographical manner similar to the ipsilateral projections. An important observation with respect to the structure of the nucleus accumbens is that the subicular terminations are inhomogeneously distributed, although a relation with earlier described mosaic patterns in the connectivity and neurochemical composition of the nucleus is not yet clear. Subicular fibres have their densest terminations in relatively cell-poor regions of the nucleus accumbens, and in particular tend to avoid small cell clusters.