Projections from the lowest thoracic and upper lumbar segments to the cerebellar cortex in the rat: An anterograde tracing study

Abstract

The projections from the lowest thoracic and upper lumbar (T13 to L3) segments to the cerebellar cortex were examined by anterograde tracing with biotinylated dextran amine in the rat. Unilateral injections resulted in bilateral labeling of mossy fiber terminals in lobules Ib to VI, VIII, IX and copula pyramidis. The majority (64 % of the total 30,526 labeled terminals) were present ipsilaterally in lobules II (8.5 %), III (20 %), IV (11 %), V (12 %), VIII (4.1 %), and copula pyramidis (6.8 %). The projection field in the anterior lobe was composed of five longitudinal areas: area 1 in the midline region, areas 2 and 3 in the middle and lateral parts of the vermis, and areas 4 and 5 in the medial part of the intermediate region of the hemisphere. The projection areas are characteristically localized in the apical to the middle part of the lobule. In the posterior lobe, the longitudinal areas were present in the midline region, the middle and lateral parts of lobules VIIIa and VIIIb, and the medial and middle parts of copula pyramidis. The present study reveals the whole areas and the pattern of projections from the segments containing the cells of origin of the dorsal and ventral spinocerebellar tracts.