Spinocerebellar projections from the lowest lumbar and sacral-caudal segments in the cat, as studied by anterograde transport of wheat germ agglutinin-horseradish peroxidase.

The projection fields of spinocerebellar tracts arising from the lowest lumbar and sacral-caudal segments were studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in the cat. Injections of WGA-HRP into these segments labeled mossy fiber terminals mainly in sublobules Ia-Vf, lobule VI, and sublobules VIIb-VIIIb. In the sagittal plane the labeled terminals were distributed in the apical part of the lobules. More than 90% of the total number were in the anterior lobe, of which 50-80% were in sublobules IIa and IIb. The labeled terminals were concentrated between 1.0 and 2.0 mm lateral to the midline. The results of injections following hemisections revealed that the projections are bilateral and that their quantity does not differ between the two sides. The projection fields in the horizontal plane were reconstructed from a series of cross sections through lobules I-III. The labeled terminals were distributed in two areas localized to the apical part of the lobules: area 1 located between 0.75 and 1.5 mm lateral to the midline in zone B of Voogd (the lateral part of the vermis) and area 2 located 2.0 mm lateral to the midline in zones C1-C3 (the intermediate region of the hemisphere). The present anterograde and previous retrograde HRP studies show that the spinocerebellar tract neurons in the medial part of lamina VII caudal to the L7 segment and in laminae V and VIII of sacral-caudal segments project mainly to lobules I-V of the anterior lobe and to lobule VI, sublobule VIIb, and lobule VIII of the posterior lobe. The projections were most abundant in sublobules IIa and IIb.