Pontine Functional Connectivity Gradients.

The cerebellum contributes to a wide range of motor and non-motor functions through its extensive connections with much of the cerebral cortex. The pons plays a key role in these connections. It receives inputs from much of the cerebral cortex, and in turn projects to cerebellar cortex. The anatomical organization of corticopontine and pontocerebellar connectivity has been well described, but the functional organization of the pons in humans remains poorly understood. In particular, it is unclear how inputs from different areas are integrated or segregated within it. We sought to characterize the functional organization of the pons based on its functional connectivity with the cerebral and cerebellar cortices. To this end, we used diffusion map embedding, a non-linear dimensionality reduction technique, to reconstruct gradients that reflect the dominant patterns of pontine functional connectivity. Our results reveal a primary gradient in the pons that is organized along rostrocaudal and mediolateral axes. We found that inputs from higher-order cognitive areas of the cerebral cortex converge on rostral and medial pons, whereas inputs from sensorimotor areas converge on the caudal and lateral pons. The organization of this gradient mirrors the unimodal-to-transmodal gradient previously described in the cerebral and cerebellar cortices. The observed patterns align with findings from invasive tract-tracing in non-human animals and extend them to demonstrate that pontine functional organization can be characterized by a complex pattern of segregation and integration. These findings highlight that, rather than serving as a simple relay, the pons may function as an integrative hub within the cortico-ponto-cerebellar pathway.