Cerebellar–M1 Connectivity Changes Associated with Motor Learning Are Somatotopic Specific

Abstract

One of the functions of the cerebellum in motor learning is to predict and account for systematic changes to the body or environment. This form of adaptive learning is mediated by plastic changes occurring within the cerebellar cortex. The strength of cerebellar-to-cerebral pathways for a given muscle may reflect aspects of cerebellum-dependent motor adaptation. These connections with motor cortex (M1) can be estimated as cerebellar inhibition (CBI): a conditioning pulse of transcranial magnetic stimulation delivered to the cerebellum before a test pulse over motor cortex. Previously, we have demonstrated that changes in CBI for a given muscle representation correlate with learning a motor adaptation task with the involved limb. However, the specificity of these effects is unknown. Here, we investigated whether CBI changes in humans are somatotopy specific and how they relate to motor adaptation. We found that learning a visuomotor rotation task with the right hand changed CBI, not only for the involved first dorsal interosseous of the right hand, but also for an uninvolved right leg muscle, the tibialis anterior, likely related to inter-effector transfer of learning. In two follow-up experiments, we investigated whether the preparation of a simple hand or leg movement would produce a somatotopy-specific modulation of CBI. We found that CBI changes only for the effector involved in the movement. These results indicate that learning-related changes in cerebellar-M1 connectivity reflect a somatotopy-specific interaction. Modulation of this pathway is also present in the context of interlimb transfer of learning.

The use of transcranial magnetic stimulation to evaluate cortical excitability of lower limb musculature: Challenges and opportunities

“…Finally, evaluation of the role of cortico-cortical connections and excitability of areas other than M1 (such as the dorsal premotor cortex, parietal cortex) in LE motor control is needed (Groppa, Schlaak, et al, 2012; Koch & Rothwell, 2009; Parmigiani, Zattera, Barchiesi, & Cattaneo, 2018). Similarly, the role of the cerebellum, which is critical for both motor and cognitive control as well as adaptation and motor learning, in training-induced neuroplasticity of LE muscles is warranted (Grimaldi et al, 2016; Jayaram, Galea, Bastian, & Celnik, 2011; Spampinato, Block, & Celnik, 2017). …”

Motor primitives in space and time via targeted gain modulation in cortical networks

“…Although the idea of using motor primitives to facilitate rapid acquisition of new movements is well established [25,26], our approach proposes the first (to our knowledge) circuit-level mechanism for achieving this objective. In addition to neuromodulatory systems [19,20,22], the cerebellum is a natural candidate structure to coordinate such motor primitives [25], as it is known to project to M1 and to play a critical role in error-based motor learning [25,35].…”

A computational pipeline to determine lobular electric field distribution during cerebellar transcranial direct current stimulation

“…During BEEMS, the neural circuits of the brain and spinal cord will respond to intrinsic (volitional drive during exercises) and extrinsic stimuli by reorganizing their structure, function, and connections, which is called neuroplasticity (Cramer et al, 2011). Here, the strength of cerebellar-tocerebral pathways for a upper limb and lower limb muscle may reflect novel somatotopy of cerebellumdependent motor adaptation (Spampinato et al, 2017) during BEEMS.…”