Anodal tDCS modulates cortical activity and synchronization in Parkinson's disease depending on motor processing

Abstract

BackgroundTranscranial direct current stimulation (tDCS) may alleviate motor symptoms in Parkinson's disease (PD). However, the neurophysiological effects of tDCS on cortical activation, synchronization, and the relation to clinical motor symptoms and motor integration need characterization.ObjectiveWe aimed to explore the effect of tDCS over the left sensorimotor area on clinical motor outcome, right hand fine motor performance as well as cortical activity and synchronization in the high beta range.MethodsIn this double-blind randomized sham-controlled clinico-neurophysiological study we investigated ten idiopathic PD patients and eleven matched healthy controls (HC) on two days during an isometric precision grip task and at rest before and after ‘verum’ and ‘sham’ anodal tDCS (20 min; 1 mA; anode [C3], cathode [Fp2]). We measured clinical outcome, fine motor performance, and analysed both cortical frequency domain activity and corticocortical imaginary coherence.ResultstDCS improved PD motor symptoms. Neurophysiological features indicated a motor-task-specific modulation of activity and coherence from 22 to 27 Hz after ‘verum’ stimulation in PD. Activity was significantly reduced over the left sensorimotor and right frontotemporal area. Before stimulation, PD patients showed reduced coherence over the left sensorimotor area during motor task compared to HC, and this increased after ‘verum’ stimulation in the motor task. The activity and synchronization modulation were neither observed at rest, after sham stimulation nor in healthy controls.ConclusionVerum tDCS modulated the PD cortical network specifically during fine motor integration. Cortical oscillatory features were not in general deregulated in PD, but depended on motor processing.

The Effect of Transcranial Direct Current Stimulation in Changing Resting-State Functional Connectivity in Patients With Neurological Disorders: A Systematic Review

“…At the whole-brain level, Wu et al 63 identified an increase in EEG coherence after applying stimulation over the left dorsolateral prefrontal cortex among 5 patients with disorders of consciousness. In contrast, another study of a larger sample size conducted by Schoellmann et al 55 found no significant differences between active and sham tDCS groups in rsFC, as indicated by imaginary corticocortical coherence across beta frequency bands among patients with Parkinson’s disease.…”

“…The included RCTs involved 348 patients in total from different age groups who suffered from a broad range of neurological disorders, including fibromyalgia, 49 inflammatory bowel disorder 50 and neuropsychiatric disorders (ie, schizophrenia, 51 , 52 substance abuse 53 ), neurodegenerative disorders (ie, multiple sclerosis, 54 Parkinson’s disease, 55 primary progressive aphasia 56 ), neurodevelopmental disorders (ie, attention-deficit/hyperactivity disorder 57 , 58 ), stroke, 59 , 60 and disorders of consciousness. 61 These studies adopted a great variety of tDCS protocols and adopted a variety of rsFC analytic methods.…”

Probing the relevance of repeated cathodal transcranial direct current stimulation over the primary motor cortex for prolongation of after‐effects

“…), Parkinson's disease (Schoellmann et al . ), depression (Brunoni et al . ) and schizophrenia (Andrade, ).…”

The Effects of Transcranial Electrical Stimulation on Human Motor Functions: A Comprehensive Review of Functional Neuroimaging Studies

“…For stroke patients, tDCS increased their hand–eye coordination ( Lefebvre et al, 2015 , 2017 ) and dexterity ( Lindenberg et al, 2010 , 2012 ; Nair et al, 2011 ; Khan et al, 2015 ; Zheng and Schlaug, 2015 ; Allman et al, 2016 ; Lee et al, 2018 , 2019 ), which could last for 1 week to 2 months. Two studies ( Del Felice et al, 2019 ; Schoellmann et al, 2019 ) have investigated tES on PD patients and have demonstrated it could improve the motor symptoms and modulate the brain oscillatory activity. These findings indicate the potential facilitation effects of tES on stroke recovery and PD symptoms.…”

“…It revealed that tDCS increased functional connectivity within the premotor, motor, and sensorimotor areas during voluntary hand movements in the high-gamma band (60–90 Hz). Schoellmann et al (2019) discovered a reduction of beta rhythm coherence in PD patients after tDCS. Because excessive beta synchronization in the beta range is a marker in PD patients, these findings could indicate the potential application of tDCS in alleviating PD symptoms.…”