Sham tDCS: A hidden source of variability? Reflections for further blinded, controlled trials

Fonteneau, Clara; Mondino, Marine; Arns, Martijn; Baeken, Chris; Bikson, Marom; Brunoni, André R.; Burke, Matthew J.; Neuvonen, Tuomas; Padberg, Frank; Pascual‐Leone, Álvaro; Poulet, Emmanuel; Ruffini, Giulio; Santarnecchi, Emiliano; Sauvaget, Anne; Schellhorn, Klaus; Suaud-Chagny, Marie-Françoise; Palm, Ulrich; Brunelin, Jérôme

doi:10.1016/j.brs.2018.12.977

Cited by 167 publications

(136 citation statements)

References 67 publications

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“…All patients tolerated the interventions without complications and most published studies report beneficial effects in several domains. Several shortcomings, however, emerge: (1) the majority of studies did not use modelling to fully capture the induced electric fields and did not optimize the "dose" for each participant; (2) protocols were different, including different electrode sizes, electrode shapes, electrode locations, intensity, and durations of the interventions; (3) sample sizes were small, often with case reports or case series; (4) few studies were sham controlled, and sham tDCS may be problematic [92,93]; (5) blinding was insufficiently assessed; and (6) outcome measures and reported benefits were variable.…”

Section: Clinical Studiesmentioning

confidence: 99%

Non-Invasive Cerebellar Stimulation in Neurodegenerative Ataxia: A Literature Review

Benussi

Pascual‐Leone

Borroni

2020

IJMS

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Cerebellar ataxias are a heterogenous group of degenerative disorders for which we currently lack effective and disease-modifying interventions. The field of non-invasive brain stimulation has made much progress in the development of specific stimulation protocols to modulate cerebellar excitability and try to restore the physiological activity of the cerebellum in patients with ataxia. In light of limited evidence-based pharmacologic and non-pharmacologic treatment options for patients with ataxia, several different non-invasive brain stimulation protocols have emerged, particularly employing repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) techniques. In this review, we summarize the most relevant rTMS and tDCS therapeutic trials and discuss their implications in the care of patients with degenerative ataxias.

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Section: Clinical Studiesmentioning

confidence: 99%

Non-Invasive Cerebellar Stimulation in Neurodegenerative Ataxia: A Literature Review

Benussi

Pascual‐Leone

Borroni

2020

IJMS

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“…3) Control condition (sham and/or active control): The usual approach for blinding a study is to use a sham stimulation (no stimulation during the session but inducing sensations at the beginning and/or end of the session via ramp up/ ramp down of current). However, inconsistency in sham-controlled studies in tDCS literature resulted in debates on whether different sham protocols are equivalent (Fonteneau et al, 2019). Another approach in blinding a study is active control, which refers to a condition where the stimulation is performed over an area irrelevant for the purpose of study.…”

Section: Tdcs-mr Imaging: Trial Design Parameter Spacementioning

confidence: 99%

Methodology for tDCS integration with fMRI

Esmaeilpour

Shereen

Ghobadi‐Azbari

et al. 2019

Preprint

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Integration of tDCS with fMRI holds promise for investigation the underlying mechanism of stimulation effect. There are 118 published tDCS studies (up to 1st Oct 2018) that used fMRI as a proxy measure of neural activation to answer mechanistic, predictive, and localization questions about how brain activity is modulated by tDCS. FMRI can potentially contribute as: a measure of cognitive state-level variance in baseline brain activation before tDCS; inform the design of stimulation montages that aim to target functional networks during specific tasks; and act as an outcome measure of functional response to tDCS. In this systematic review we explore methodological parameter space of tDCS integration with fMRI. Existing tDCS-fMRI literature shows little replication across these permutations; few studies used comparable study designs. Here, we use a case study with both task and resting state fMRI before and after tDCS in a cross-over design to discuss methodological confounds. We further outline how computational models of current flow should be combined with imaging data to understand sources of variability in responsiveness. Through the case study, we demonstrate how modeling and imaging methodology can be integrated for individualized analysis. Finally, we discuss the importance of conducting tDCS-fMRI with stimulation equipment certified as safe to use inside the MR scanner, and of correcting for image artifacts caused by tDCS. tDCS-fMRI can address important questions on the functional mechanisms of tDCS action (e.g. target engagement) and has the potential to support enhancement of behavioral interventions, provided studies are designed rationally.

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“…Beyond the single or double blinding efficacy of FISSFO and related approaches [14], an element of interest is the question of whether tDCS effects are due to cortical interaction of the generated electric fields or from Peripheral Nervous System (PNS) stimulation. Since the ramp-up/ramp-down method for blinding decreases both cortical and peripheral stimulations, they cannot help disentangling cortical and peripheral effects.…”

Section: Introductionmentioning

confidence: 99%

A novel tDCS sham approach based on model-driven controlled shunting

et al. 2020

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Background: Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique able to transiently modulate brain activity, is surging as one of the most promising therapeutic solutions in many neurological and psychiatric disorders. However, profound limitations exist in current placebo (sham) protocols that limit single-and double-blinding, especially in non-naïve subjects. Objective: To ensure better blinding and strengthen reliability of tDCS studies and trials, we tested a new optimization algorithm aimed at creating an "active" sham tDCS condition (ActiSham hereafter) capable of inducing the same scalp sensations perceived during real stimulation while preventing currents from reaching the cortex and cause changes in brain excitability. Methods: A novel model-based multielectrode technique d optimizing the location and currents of a set of small electrodes placed on the scalp d was used to control the relative amount of current delivered transcranially in real and placebo multichannel tDCS conditions. The presence, intensity and localization of scalp sensations during tDCS was evaluated by means of a specifically designed questionnaire administered to the participants. We compared blinding ratings by directly addressing subjects' ability to discriminate across conditions for both traditional (Bifocal-tDCS and Sham, using sponge electrodes) and our novel multifocal approach (both real Multifocal-tDCS and ActiSham). Changes in corticospinal excitability were monitored based on Motor Evoked Potentials (MEPs) recorded via concurrent Transcranial Magnetic Stimulation (TMS) and electromyography (EMG). Results: Participants perceived Multifocal-tDCS and ActiSham similarly in terms of both localization and intensity of scalp sensations, whereas traditional Bifocal stimulation was rated as more painful and annoying compared to its Sham counterpart. Additionally, differences in scalp localization were reported for active/sham Bifocal-tDCS, with Sham tDCS inducing more widespread itching and burning sensations. As for MEPs amplitude, a main effect of stimulation was found when comparing Bifocal-Sham and ActiSham (F (1,13) ¼ 6.67, p ¼ .023), with higher MEPs amplitudes after the application of Bifocal-Sham. Conclusions: Compared to traditional Bifocal-tDCS, ActiSham offers better participants' blinding by inducing very similar scalp sensations to those of real Multifocal tDCS both in terms of intensity and localization, while not affecting corticospinal excitability.

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Sham tDCS: A hidden source of variability? Reflections for further blinded, controlled trials

Cited by 167 publications

References 67 publications

Non-Invasive Cerebellar Stimulation in Neurodegenerative Ataxia: A Literature Review

Non-Invasive Cerebellar Stimulation in Neurodegenerative Ataxia: A Literature Review

Methodology for tDCS integration with fMRI

A novel tDCS sham approach based on model-driven controlled shunting

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