Anodal transcranial direct current stimulation with monopolar pulses improves limb use after stroke by enhancing inter-hemispheric coherence

Andrea G P Schjetnan,Artur Luczak,Gerlinde A.S Metz,Darryl C Gidyk

doi:10.21307/ane-2019-027

Andrea G P Schjetnan, Artur Luczak + Show 2 more

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https://doi.org/10.21307/ane-2019-027

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Abstract

Post-stroke neurological deficits, such as sensorimotor impairments, are often permanent and a leading cause of disability. Stroke is also associated with changes in neuronal synchrony among different brain areas. Multiple studies demonstrated that non-invasive brain stimulation, such as transcranial direct current stimulation (tDCS), enhances the efficacy of existing rehabilitative therapies. We hypothesized that the therapeutic effects of tDCS could be due to its influence on neuronal synchrony. To study this, we recorded local field potentials in rats treated with anodal tDCS (a-tDCS) after unilateral ischemic motor cortex lesion. To enhance the effect of a-tDCS on neuronal synchrony, we added monopolar pulses (a-tDCSmp) during a treatment. We found that ischemic lesions reduced interhemispheric coherence in the low gamma frequency range. By contrast, a-tDCSmp treatment increased interhemispheric coherence along with motor improvement in a skilled reaching task. These observations indicate that increased neuronal coherence is a likely mechanism by which tDCS improves stroke recovery. Moreover, this work adds to previous evidence that measures of brain coherence could be used as a biomarker of stroke recovery, which may help in the design of more effective tDCS protocols for stroke rehabilitation.

Highlights

Stroke is characterized by reduced blood flow to the brain
To investigate how interactions between sensory areas change after stroke and how this is modified by the application of electrical stimulation, three groups of rats were studied: Control (n=5), Stroke (n=5), and a group with stroke treated with direct current stimula‐ tion (Stroke+Stim, n=5)
Cal networks in rats treated with a‐tDCSmp after a fo‐ cal ischemic motor cortex lesion

Summary

Introduction

Stroke is characterized by reduced blood flow to the brain. It represents the leading cause of chronic adult disability and the third leading cause of death in North America (Benjamin et al, 2017). Post‐stroke neuroplasticity includes regeneration of damaged pathways, axonal and dendritic sprouting, and remapping of functional representations (Adkins et al, 2002; Winship and Murphy, 2009; Westlake and Nagarajan, 2011). Studies using resting state function‐ al magnetic resonance imaging (fMRI) reported that post‐stroke loss and recovery of sensorimotor function is associated with acute deterioration and subsequent retrieval of interhemispheric functional connectiv‐ ity within the sensorimotor system (van Meer et al, 2010; 2012; Westlake and Nagarajan, 2011). Clinical rehabilitative strategies take advantage of this infor‐ mation, for example by using bilateral arm training (Coupar et al, 2010; Choo et al, 2015), and improve‐ ments in stroke rehabilitation correlated with increas‐ es in inter‐hemispheric coupling in EEG (Pellegrino et al, 2012)

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