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

Abstract

The projection fields of spinocerebellar tracts arising from the cervical enlargement were studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in the cat. Following injections of WGA-HRP into the C5-C8 or T1 segments, labeled terminals were seen in lobule I to sublobule Vf of the anterior lobe, and lobule VI, sublobule VIIb, lobules VIII and IX, the simple lobule, crus II, and the paramedian lobule of the posterior lobe. In the sagittal plane of sublobules Ib-Vf and sublobules VIf and VId, the labeled terminals were distributed mainly in the superficial two thirds of the apicobasal extent. The labeled terminals in the anterior lobe accounted for about 70% of the total labeled terminals; the great majority were in lobule IV (17-20%) and lobule V (40%). The labeled terminals in the posterior lobe accounted for 30% of the total labeled terminals; the majority were in sublobules VIf (11-15%) and VId (6%). In the mediolateral extent, more than 50% of the total labeled terminals in each lobule were concentrated within 1.0 mm from the midline (the vermis) and 70-80% within 2.0 mm from the midline (the vermis and the medial part of the intermediate regions). A smaller number were also present in the intermediate region. Cases with lateral cordotomies revealed that the projections were bilateral but predominantly ipsilateral to the cells or origin and that the quantity of the ipsilateral projection was 66.5-75% of the total in each of sublobules IVb, Va, and VIf. The projection to the paramedian lobule was also predominantly ipsilateral. Projection fields in the horizontal plane were reconstructed from a series of transverse sections through each lobule. In sublobules Va-VIf labeled terminals were distributed in three areas: area 1 located within 0.25 mm from the midline in zone A1 of Voogd; area 2 located between 0.5 and 0.75 mm lateral to the midline in zones A1 and A2; and area 3, which appeared to be located between 0.75 and 1.5 mm lateral to the midline in zones A2-B. These areas extended longitudinally in the apical two thirds of the lobules. From the present and previous retrograde HRP studies it was suggested that the neuronal groups in the cervical enlargement (the medial lamina VI group and the central lamina VII group) project to lobules I-V of the anterior lobe and lobule VI, sublobule VIIb, and lobule VIII of the posterior lobe. They have strong projections to caudal lobules of the anterior lobe (lobules III-Va) and lobules facing the primary fissure (sublobules Vd-Vf and sublobules VIf and VId).