The dorsal spino-olivocerebellar system in the cat. II. Somatotopical organization.

The somatotopical organization of the projection through the dorsal spino-olivocerebellar path (DF-SOCP) to the c3 zone in the cerebellar anterior lobe was studied by recording climbing fiber field potentials in the cerebellar cortex evoked on stimulation of peripheral nerves. The c3 zone was shown to contain a detailed and systematic representation of the ipsilateral body half with the follwing characteristics: 1. Single nerves project to one or two sagittal strips of cortex which extend across several folia. The width of the strips varies between 0.2 and 1 mm and the length may be as long as 15-20 mm along the unfolded cortex. 2. The strips activated from different nerves occur in an order which usually follows the segmental innervation, the hindlimb being represented rostrally and the forelimb caudally in the zone. 3. The double representation of some nerves makes it possible to distinguish one medial and one lateral part of the c3 zone with the projection areas organized approximately as mirror images. Additional observations on other zones activated by the DF-SOCP system (Ekerot and Larson, 1979a) indicate that the c1 zone, has a somatotopical organization which is reminiscent of that of the c3 zone, whereas the x and d1 zones have different topographical organizations.