A Single Session of Anodal Cerebellar Transcranial Direct Current Stimulation Does Not Induce Facilitation of Locomotor Consolidation in Patients With Multiple Sclerosis.

Carine Nguemeni,Mirko Pham,Daniel Zeller,Jens Volkmann,Luis Nakchbandi,György A Homola

doi:10.3389/fnhum.2020.588671

Abstract

Background: Multiple sclerosis (MS) may cause variable functional impairment. The discrepancy between functional impairment and brain imaging findings in patients with MS (PwMS) might be attributed to differential adaptive and consolidation capacities. Modulating those abilities could contribute to a favorable clinical course of the disease.Objectives: We examined the effect of cerebellar transcranial direct current stimulation (c-tDCS) on locomotor adaptation and consolidation in PwMS using a split-belt treadmill (SBT) paradigm.Methods: 40 PwMS and 30 matched healthy controls performed a locomotor adaptation task on a SBT. First, we assessed locomotor adaptation in PwMS. In a second investigation, this training was followed by cerebellar anodal tDCS applied immediately after the task ipsilateral to the fast leg (T0). The SBT paradigm was repeated 24 h (T1) and 78 h (T2) post-stimulation to evaluate consolidation.Results: The gait dynamics and adaptation on the SBT were comparable between PwMS and controls. We found no effects of offline cerebellar anodal tDCS on locomotor adaptation and consolidation. Participants who received the active stimulation showed the same retention index than sham-stimulated subjects at T1 (p = 0.33) and T2 (p = 0.46).Conclusion: Locomotor adaptation is preserved in people with mild-to-moderate MS. However, cerebellar anodal tDCS applied immediately post-training does not further enhance this ability. Future studies should define the neurobiological substrates of maintained plasticity in PwMS and how these substrates can be manipulated to improve compensation. Systematic assessments of methodological variables for cerebellar tDCS are urgently needed to increase the consistency and replicability of the results across experiments in various settings.

Highlights

Multiple sclerosis (MS) is an inflammatory disease that affects the CNS by demyelination and neurodegeneration (Dobson and Giovannoni, 2019)
Expanded Disability Status Scale (EDSS) scores correlated with performance on the T25FWT (r = 0.83, p = 0.003), but not with disease duration (r = −0.006, p = 0.99) as expressed by the Spearman correlation
We found no difference in the T25FWT, X2(3) = 6.4, p = 0.094 between HC and people with MS (PwMS)

Summary

Introduction

Multiple sclerosis (MS) is an inflammatory disease that affects the CNS by demyelination and neurodegeneration (Dobson and Giovannoni, 2019). Motor memory is transformed from an initially fragile to a more robust state and therewith gains resistance to interference This timedependent process, called consolidation, determines the ability to recall and build upon adapted motor patterns across days and in new environmental conditions (Robertson et al, 2004; Krakauer and Shadmehr, 2006). The discrepancy between functional impairment and brain imaging findings in patients with MS (PwMS) might be attributed to differential adaptive and consolidation capacities. Modulating those abilities could contribute to a favorable clinical course of the disease

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Discussion

Conclusion