Cerebellar outputs contribute to spontaneous and movement-related activity in the motor cortex of monkeys

Cerebellar outputs originate from the dentate nucleus (DN), project to the primary motor cortex (M1) via the motor thalamus, control M1 activity, and play an essential role in coordinated movements. However, it is unclear when and how the cerebellar outputs contribute to M1 activity. To address this question, we examined the response of M1 neurons to electrical stimulation of the DN and M1 activity during performance of arm-reaching tasks. Based on response patterns to DN stimulation, M1 neurons were classified into facilitation-, suppression-, and no-response-types. During tasks, not only facilitation- and suppression-type M1 neurons, but also no response-type M1 neurons increased or decreased their firing rates in relation to arm reaching movements. However, the firing rates of facilitation- and suppression-type neurons were higher than those of no-response-type neurons during both inter-trial intervals and arm reaching movements. These results imply that cerebellar outputs contribute to both spontaneous and movement-related activity in the M1, which help to maintain muscle tones and execute coordinated movements, although other inputs also contribute to movement-related activity. Pharmacological inactivation of the DN supports this notion, in that DN inactivation reduced both spontaneous firing rates and movement-related activity in the M1. (C) 2020 Elsevier B.V. and Japan Neuroscience Society. All rights reserved.

Automated summary

Cerebellar outputs from the dentate nucleus (DN) influence activity in the primary motor cortex (M1) during both spontaneous and movement-related activity. Different types of M1 neurons show varied responses to DN stimulation, with facilitation- and suppression-type neurons exhibiting higher firing rates compared to no-response-type neurons during arm reaching tasks. Pharmacological inactivation of the DN reduces both spontaneous firing rates and movement-related activity in the M1.