Fig. 2.

Two distinct cerebellar–cerebral pathways. Schematic depicting two proposed interconnections between the cerebellum and M1. DN Dentate nucleus, VL ventral lateral section of thalamus, PMC premotor cortex. Recent work has shown that separate cerebellar–thalamus pathways interact with both early (e.g., monosynaptic, PA) and late (e.g., polysynaptic, AP) I-waves. It has been suggested that the cerebellar AP pathway may involve projects to the PMC that then are relayed to M1 (Volz et al. 2014; Spampinato et al. 2020). Alternatively, it is possible that back-propagating action potentials within M1 can also play role in the effects described by Spampinato and others (2020), as cerebellar stimulation has been suggested to preferentially affect late I-waves (Iwata and Ugawa 2005; Ugawa et al. 2019)