1 Department of Psychology, Concordia University, Montreal, Canada. paul.rousseau@mail.mcgill.ca.
2 Full brain picture Analytics, Leiden, The Netherlands.
3 Department of Psychology, Concordia University, Montreal, Canada.
4 School of Health, Concordia University, Montreal, Canada.
5 Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.

The cerebellum's involvement in a range of cognitive, emotional, and motor processes has become increasingly evident. Given the uniformity of the cerebellar cortex's cellular architecture its contributions to varied processes are thought be partially mediated by its patterns of reciprocal connectivity with the rest of the brain. A better understanding of these connections is therefore fundamental to disentangling the cerebellum's contribution to cognition and behavior. While these connections have been studied extensively in non-human animals using invasive methods, we have limited knowledge of these connections in humans. The current work reconstructed the corticopontine projection, the first segment of downstream connections between the cerebral and cerebellar cortices, with diffusion MRI tractography in human in-vivo whole brain data and an independent higher resolution postmortem brainstem dataset. Dimensionality reduction was used to characterize the pattern of connectivity of cerebral cortical projections to the pons as two overlapping gradients that were consistent across participants and datasets: medial to lateral and core to belt. Our findings align with invasive work done in animals and advance our understanding of this connection in humans - providing valuable context to a growing body of cerebellar research, offering insights into impacts of damage along the pathway, and informing clinical interventions.