Spinal, trigeminal, and cortical climbing fibre paths to the lateral vermis of the cerebellar anterior lobe in the cat.

The spinal, trigeminal and cortical climbing fibre projection to the lateral vermis of the cerebellar anterior lobe in the cat has been investigated. The b zone, which occupies a one mm wide band in the lateral vermis, receives a somatotopically arranged input. Successively more rostral segments (tail, hindlimb, thorax, forelimb and trigeminal nerves) project to successively more medial microzones. The b zone receives an input through each of three spino-olivocerebellar paths (SOCPs) ascending in the ventral, dorsal and dorsolateral funiculi (VF, DF and DLF). In the b zone, the hindlimb input is bilateral through the VF-SOCP and ipsilateral through he DF- and DLF-SOCPs. The forelimb input is bilateral through the VF-SOCP, ipsilateral through the DLF-SOCP and lacking from the DF-SOCP. The trigeminal input is bilateral. Medial to the b zone in lobule V is the x zone, which receives an input from the ipsilateral forelimb through the DF- and DLF-SOCPs. The climbing fibres to the x zone are collaterals of the climbing fibres projecting to the c1 zone in the pars intermedia and paramedian lobule. The climbing fibre input from the cerebral sensorimotor cortex to the lateral vermis matches the spinal input. The lateral and medial parts of the b zone receive a bilateral input from hind- and forelimb cortical areas, respectively. The x zone receives an input from the contralateral forelimb area. The functional significance of the converging paths is discussed.