The indirect corticopontine pathway relays perioral sensory signals to the cerebellum via the mesodiencephalic junction

In the cerebro-cerebellar loop, outputs from the cerebral cortex are thought to be transmitted via monosynaptic corticopontine gray (PG) pathways and subse-quently relayed to the cerebellum. However, it is unclear whether this pathway is used constitutively for cerebro-cerebellar transduction. We examined perioral sensory pathways by unit recording from Purkinje cells in ketamine/xylazine-anesthetized mice. Infraorbital nerve stimulations enhanced simple spikes (SSs) with short and long latencies (first and second peaks), followed by SS inhibition. The second peak and SS inhibition were suppressed by muscimol (a GABAA agonist) injections into not only the PG but also the mesodiencephalic junction (MDJ). The pathway from the secondary somatosensory area (SII) to the MDJ, but not the cortico-PG pathway, transmitted the second peak signals. SS inhibi-tion was processed in the SII and primary motor area. Thus, the indirect cortico-PG pathway, via the MDJ, is recruited for perioral sensory transduction.

Automated summary

In the cerebro-cerebellar loop, the indirect cortico-PG pathway via the mesodiencephalic junction (MDJ) is recruited for perioral sensory transduction. Stimulation of the infraorbital nerve results in enhanced simple spikes (SSs) with short and long latencies, followed by SS inhibition. The second peak signals and SS inhibition are transmitted through the secondary somatosensory area (SII) to the MDJ.