Fronto-cerebellar circuits and eye movement control: a diffusion imaging tractography study of human cortico-pontine projections.

A possible role of the cerebellum in cognitive function might be revealed through its anatomical connections with specific regions of the cerebral cortex. To understand the kind of information transmitted between the cortex and cerebellum, we studied the connections from six subdivisions of frontal and prefrontal cortex using diffusion imaging tractography. Cortico-pontine fibers travel through the cerebral peduncles and reach the cerebellum by way of a synaptic link in the pontine nuclei. In 19 human data sets, we tracked connections between the cerebral peduncle and left hemispheric masks of the superior frontal gyrus (SFG), precentral gyrus (PcG), middle frontal gyrus (MFG), orbital frontal cortex, and two regions of inferior frontal gyrus, including pars opercularis and pars triangularis. Cortico-pontine fibers arose from the PcG, the caudal/medial SFG and a small region of the MFG in a majority of the subjects analyzed. While these regions do have known roles in cognitive and executive functions, all three are strongly associated with the planning and execution of eye movements. Connections from more ventral prefrontal cortex were negligible, indicating that these regions are only sparsely represented in the circuit. Based on this pattern of connectivity, it is likely that the prefrontal connections to the cerebellum are involved in covert motor operations and the control of eye movements.