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

The projection fields of the dorsal spinocerebellar tract (DSCT) arising from Clarke's column, marginal neurons of Clarke's column, and lamina V neurons in the upper lumbar segments were studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in the cat. To label only these neuron groups with uncrossed ascending axons, the spinal cord was lesioned rostral and contralateral to the WGA-HRP injections. Following injections of WGA-HRP into the L1-L4 segments, labeled terminals were seen in sublobules Ia-VIc and VIIb-VIIIb, the simple lobule, the paramedian lobule, and the dorsal paraflocculus. About 70-80% and 20-30% of the total number of labeled terminals were in the anterior and the posterior lobe, respectively; the projections were predominantly ipsilateral to the cells of origin (about 87% or more labeled terminals of the total number in each of sublobules IIb-Va). The labeled terminals were abundant in sublobule IIb (6-11%), lobule III (12-27%), and sublobules IVa (14-17%) and IVb (14-21%). In the mediolateral extent of the lobules in the anterior lobe, the labeled terminals were most numerous between 1.1 and 3.0 mm lateral to the midline (45-75% of the total number of labeled terminals on the ipsilateral side). In the posterior lobe labeled terminals were numerous in sublobule VIIIb (13.6%) and sublobule C of the paramedian lobule (15-19%). The projection fields in the horizontal plane of the lobules were reconstructed from a series of cross sections through each lobule. In the anterior lobe the labeled terminals were distributed in eight major areas. In sublobules IIb-III, areas 1-3 were located within 1.0 mm of the midline in zone A of Voogd; areas 4-6, between 1.0 and 2.5 mm lateral to the midline in zones B-C1; and areas 7 and 8, lateral to 3.0 mm from the midline in zones C2 and C3. Areas 1-6 extended apicobasally in the middle part of the lobules. In sublobule VIIIb projections were confined to three longitudinal areas whereas in the paramedian lobule the projection areas were less distinct. The projection pattern of the lumbar DSCT was different from that of the thoracic DSCT reported previously. In the anterior lobe the thoracic DSCT projects to five areas in the medial (zone A) and the lateral part (zone B) of the vermis and to four areas in the intermediate region of the hemisphere (zones C1-C3).