Blinding is compromised for transcranial direct current stimulation at 1 <scp>mA</scp> for 20 min in young healthy adults

Turi, Zsolt; Csifcsák, Gábor; Boayue, Nya Mehnwolo; Aslaksen, Per M.; Antal, Andrea; Paulus, Walter; Groot, Josephine Maria; Hawkins, Guy E.; Forstmann, Birte U.; Opitz, Alexander; Thielscher, Axel; Mittner, Matthias

doi:10.1111/ejn.14403

Cited by 80 publications

(59 citation statements)

References 34 publications

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“…Because real tACS can induce both cutaneous and visual perceptual adverse effects during the entire stimulation period, we preferred using a control tACS protocol, instead of a sham tACS protocol (Turi et al, 2013). The conventionally used fade-in, short-stimulation, fade-out sham protocols, may not be able to maintain effective blinding for the real intervention because of their shortness, as has been shown for transcranial direct current stimulation (Greinacher et al, 2019;Turi et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

θ-γ Cross-Frequency Transcranial Alternating Current Stimulation over the Trough Impairs Cognitive Control

Turi

Mittner

Lehr

et al. 2020

eNeuro

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Cognitive control is a mental process, which underlies adaptive goal-directed decisions. Previous studies have linked cognitive control to electrophysiological fluctuations in the u band and u-g cross-frequency coupling (CFC) arising from the cingulate and frontal cortices. However, to date, the behavioral consequences of different forms of u-g CFC remain elusive. Here, we studied the behavioral effects of the u-g CFC via transcranial alternating current stimulation (tACS) designed to stimulate the frontal and cingulate cortices in humans. Using a double-blind, randomized, repeated measures study design, 24 healthy participants were subjected to three active and one control CFC-tACS conditions. In the active conditions, 80-Hz g tACS was coupled to 4-Hz u tACS. Specifically, in two of the active conditions, short g bursts were coupled to the delivered u cycle to coincide with either its peaks or troughs. In the third active condition, the phase of a u cycle modulated the amplitude of the g oscillation. In the fourth, control protocol, 80-Hz tACS was continuously superimposed over the 4-Hz tACS, therefore lacking any phase specificity in the CFC. During the 20 min of stimulation, the participants performed a Go/NoGo monetary reward-based and punishment-based instrumental learning task. A Bayesian hierarchical logistic regression analysis revealed that relative to the control, the peak-coupled tACS had no effects on the behavioral performance, whereas the trough-coupled tACS and, to a lesser extent, amplitude-modulated tACS reduced performance in conflicting trials. Our results suggest that cognitive control depends on the phase specificity of the u-g CFC.

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Section: Discussionmentioning

confidence: 99%

θ-γ Cross-Frequency Transcranial Alternating Current Stimulation over the Trough Impairs Cognitive Control

Turi

Mittner

Lehr

et al. 2020

eNeuro

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“…The effect of subjective intervention 6 (Fonteneau et al, 2019;O'connell et al, 2012;Turi et al, 2019;Wallace et al, 2016). Notably, ineffective blinding is likely to mask or inflate the observed findings.…”

Section: Blinding and Subjective Interventionmentioning

confidence: 99%

The Importance of Individual Beliefs in Assessing Treatment Efficacy: Insights from Neurostimulation Studies

Fassi

Kadosh

2020

Preprint

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In recent years, there has been debate about the effectiveness of interventions from different fields (e.g., non-invasive brain stimulation (NIBS), neurofeedback, cognitive training programs) due to contradictory and nuanced experimental findings. Up to date, studies are focused on comparing the effects of an active form of the intervention to a placebo/control condition. However, a neglected question is how to consider individual differences in response to blinding procedures, and their effect on behavioural outcomes, rather than merely compare the efficacy of blinding using a group-based approach. To address this gap in the literature, we here suggest using subjective intervention—the participants’ subjective beliefs about receiving or not receiving an intervention—as a factor. Specifically, we examined whether subjective intervention and subjective dosage (i.e. participants’ subjective beliefs about the intensity of the intervention they received) affected performance scores independently, or interacting with, the active experimental condition. We carried out data analysis on an open-access dataset that has shown the efficacy of active NIBS in altering mind wandering. We show that subjective intervention and subjective dosage successfully explained alteration in mind wandering scores, over and beyond the objective intervention. These findings highlight the importance of accounting for the participants’ beliefs about receiving interventions at the individual level by demonstrating their effect on human behaviour independently of the actual intervention. Altogether, our approach allows more rigorous and improved experimental design and analysis, which will strengthen the conclusions coming from basic and clinical research, for both NIBS and non-NIBS interventions.

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“…Lastly, Subject 1 was able to correctly identify the stimulation condition (tDCS or Sham) in each session and, therefore, placebo effects cannot be dismissed. Difficulty with blinding maintenance is common in tDCS [ 70 , 71 ] and should be addressed in future study designs.…”

Section: Discussionmentioning

confidence: 99%

Different Effects of Transcranial Direct Current Stimulation on Leg Muscle Glucose Uptake Asymmetry in Two Women with Multiple Sclerosis

et al. 2020

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Asymmetrical lower limb strength is a significant contributor to impaired walking abilities in people with multiple sclerosis (PwMS). Transcranial direct current stimulation (tDCS) may be an effective technique to enhance cortical excitability and increase neural drive to more-affected lower limbs. A sham-controlled, randomized, cross-over design was employed. Two women with MS underwent two 20 min sessions of either 3 mA tDCS or Sham before 20 min of treadmill walking at a self-selected speed. During walking, the participants were injected with the glucose analogue, [18F] fluorodeoxyglucose (FDG). Participants were then imaged to examine glucose metabolism and uptake asymmetries in the legs. Standardized uptake values (SUVs) were compared between the legs and asymmetry indices were calculated. Subject 2 was considered physically active (self-reported participating in at least 30 min of moderate-intensity physical activity on at least three days of the week for the last three months), while Subject 1 was physically inactive. In Subject 1, there was a decrease in SUVs at the left knee flexors, left upper leg, left and right plantar flexors, and left and right lower legs and SUVs in the knee extensors and dorsiflexors were considered symmetric after tDCS compared to Sham. Subject 2 showed an increase in SUVs at the left and right upper legs, right plantar flexors, and right lower leg with no muscle group changing asymmetry status. This study demonstrates that tDCS may increase neural drive to leg muscles and decrease glucose uptake during walking in PwMS with low physical activity levels.

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Blinding is compromised for transcranial direct current stimulation at 1 mA for 20 min in young healthy adults

Cited by 80 publications

References 34 publications

θ-γ Cross-Frequency Transcranial Alternating Current Stimulation over the Trough Impairs Cognitive Control

θ-γ Cross-Frequency Transcranial Alternating Current Stimulation over the Trough Impairs Cognitive Control

The Importance of Individual Beliefs in Assessing Treatment Efficacy: Insights from Neurostimulation Studies

Different Effects of Transcranial Direct Current Stimulation on Leg Muscle Glucose Uptake Asymmetry in Two Women with Multiple Sclerosis

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