Non-invasive Cerebellar Stimulation—a Consensus Paper

Abstract

The field of neurostimulation of the cerebellum either with transcranial magnetic stimulation (TMS; single pulse or repetitive (rTMS)) or transcranial direct current stimulation (tDCS; anodal or cathodal) is gaining popularity in the scientific community, in particular because these stimulation techniques are non-invasive and provide novel information on cerebellar functions. There is a consensus amongst the panel of experts that both TMS and tDCS can effectively influence cerebellar functions, not only in the motor domain, with effects on visually guided tracking tasks, motor surround inhibition, motor adaptation and learning, but also for the cognitive and affective operations handled by the cerebro-cerebellar circuits. Verbal working memory, semantic associations and predictive language processing are amongst these operations. Both TMS and tDCS modulate the connectivity between the cerebellum and the primary motor cortex, tuning cerebellar excitability. Cerebellar TMS is an effective and valuable method to evaluate the cerebello-thalamo-cortical loop functions and for the study of the pathophysiology of ataxia. In most circumstances, DCS induces a polarity-dependent site-specific modulation of cerebellar activity. Paired associative stimulation of the cerebello-dentato-thalamo-M1 pathway can induce bidirectional long-term spike-timing-dependent plasticity-like changes of corticospinal excitability. However, the panel of experts considers that several important issues still remain unresolved and require further research. In particular, the role of TMS in promoting cerebellar plasticity is not established. Moreover, the exact positioning of electrode stimulation and the duration of the after effects of tDCS remain unclear. Future studies are required to better define how DCS over particular regions of the cerebellum affects individual cerebellar symptoms, given the topographical organization of cerebellar symptoms. The long-term neural consequences of non-invasive cerebellar modulation are also unclear. Although there is an agreement that the clinical applications in cerebellar disorders are likely numerous, it is emphasized that rigorous large-scale clinical trials are missing. Further studies should be encouraged to better clarify the role of using non-invasive neurostimulation techniques over the cerebellum in motor, cognitive and psychiatric rehabilitation strategies.

Intermittent Theta-Burst Stimulation of the Lateral Cerebellum Increases Functional Connectivity of the Default Network

“…Our findings are consistent with neuroplastic effects within motor cortex from noninvasive brain stimulation (for review, see Grimaldi et al, 2014). TMS to lateral locations within the cerebellum has been demonstrated to have an effect on motor circuits (Koch et al, 2008).…”

Cerebellar transcranial static magnetic field stimulation transiently reduces cerebellar brain inhibition

“…Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) over the motor cortex can modulate the excitability of the primary motor cortex (M1) (Priori et al, 2009;Grimaldi et al, 2014), because rTMS changes the efficiency of excitatory synaptic transmission (Funke and Benali, 2011), while tDCS modulates the resting membrane potential of neurons (Filmer et al, 2014). Non-invasive brain stimulation techniques are frequently used and studied for their potential applications in physical medicine and rehabilitation (Hoyer and Celnik, 2011;Adeyemo et al, 2012;Wessel et al, 2015).…”

Physical Therapy for Cerebellar Ataxia

“…The motor-evoked potential induced by transcranial magnetic stimulation (TMS) over the primary motor cortex is inhibited by TMS over the contralateral cerebellum [95,96]. This cerebellar brain inhibition (CBI) [95,[97][98][99][100][101][102][103] is modulated in patients with cerebellar ataxia [99,103] and in healthy adults after motor learning [32], indicating that CBI reflects excitability of the cerebellum and the function of connectivity of the cerebellum and other tissues associated with motor control and learning [104].…”

“…NIBS, which is repetitive TMS (rTMS) [96,98] and transcranial direct current stimulation (tDCS) [124], over the primary motor cortex can modulate the excitability of the motor cortex [125] and is often used as an effective tool for enhancing behavioral training after stroke with hemiplegia [125][126][127][128]. Furthermore, the NIBS to the cerebellum modulates cerebellar excitability [98,[129][130][131], motor function [132,133], and motor learning [32,[134][135][136][137][138] in healthy population.…”