Figure 1.

Schematics of the two loop circuits in the Guillain–Mollaret triangle. The dentato-olivo-cerebellar loop (short loop, blue) and the cerebrocerebellar loop (long loop, magenta). Smaller GABAergic (inhibitory) cells in the dentate nucleus (D) pass through the superior cerebellar peduncle (SCP) (sp), cross the midline, and project directly to the contralateral inferior olivary nucleus (O). Efferent fibers from IO pass through the inferior cerebellar peduncle (ip) and project to Purkinje cells (PC, pc) in the contralateral cerebellar hemisphere (Cbl-h). PCs then project to DN cells to close the loop. The long loop is almost identical to the cerebrocerebellar loop. Larger excitatory DN cells pass through (SCP, sp), cross the midline, and project to the contralateral parvocellular red nucleus (RNp), and the thalamus (Th) with collaterals. Thalamocortical neurons relay the cerebellar inputs to various cortical areas (Cx). The return path to the cerebellum is the cortico-ponto-cerebellar tract, which originates from a various parts of the cerebral cortex. The corticofugal axons project directly to the PN (P) and finally arrive at the contralateral cerebellar hemisphere (Cbl-h) as mossy fibers (MFs) via the middle cerebellar peduncle (mp) to close the loop.