The Human Substantia Nigra and Ventral Tegmental Area
Based on the visualization of neuromelanin-pigmented neurons, the SN can easily be distinguished in the mesencephalon macroscopically (locus niger crurum cerebri, Vicq d’Azyr 1786). The SN is generally subdivided into a cell-dense pars compacta and a cell-sparse pars reticulata. A pars lateralis extends from the lateral border of A9 toward the dorsolaterally situated corpus geniculatum mediale (Bauer 1909) and was described as area M by Sano (1910). Various subdivisions of the human SN and related structures such as the VTA have been suggested. The historical differences in nomenclature are shown in Fig. 12. Criteria used for subdivision of the SN variably stressed cytological (Poirier et al. 1983; Braak and Braak 1986), hodological (François et al. 1985; Parent 1986), and immunohistochemical (Waters et al. 1988) data, leading to a sometimes rather confusing nomenclature. Several atlasses with subdivisions of mesencephalic CAergic cell masses in the human brain are available (Foix and Nicolesco 1925; Winkler 1929; Hassler 1937; Riley 1943; Olszewski and Baxter 1954; Crosby et al. 1962; Nieuwenhuys et al. 1988). The classic work of Foix and Nicolesco (1925) is of special value, since it includes data on the SN in aging and in Parkinson’s disease. The same holds for the detailed studies of Hassler (1937, 1938), although his extensive description of pars compacta subnuclei (Fig. 32a) is hardly applicable. The variation among the smallest of Hassler’s (1937) subareas is simply too extensive. Olszewski and Baxter’s (1954) atlas gives a clear view of Nissl-stained sections.
KeywordsTyrosine Hydroxylase Caudate Nucleus Superior Colliculus DAergic Neuron Human Substantia Nigra
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