Author response for "The Time Course of Ineffective Sham Blinding During Low-Intensity (1mA) Transcranial Direct Current Stimulation"

Greinacher, Robert; Buhôt, Larissa; Möller, Lisa; Learmonth, Gemma

doi:10.1111/ejn.14497/v2/response1

Cited by 2 publications

(33 citation statements)

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“…Our results in Greinacher et al, (2019) partially conflict with those observed in Ambrus et al, (2012), where multiple (although fewer, at only 7) online probes were presented during stimulation. Participants were asked to report the location and strength of scalp sensations every 1.75min during 10min of 1mA anodal and cathodal tDCS, plus a 30s sham condition.…”

Section: Introductioncontrasting

confidence: 99%

“…Specifically, participants were expected to report that the stimulation was switched on for a longer duration in the active condition compared to our observations during 1mA. Although in Greinacher et al, (2019) we found no tDCS-induced changes in reaction time during 1mA stimulation, we hypothesised that a higher, 2mA current may lead to improvements in this outcome measure.…”

Section: Introductioncontrasting

confidence: 54%

“…In this study we aimed to extend our results in Greinacher et al, (2019) by repeating the experiment at a higher-intensity current of 2mA rather than 1mA. We predicted that participants would find it easier to identify the presence and absence of stimulation during both active and sham tDCS when 2mA is delivered, due to stronger sensations on the scalp.…”

Section: Introductionmentioning

confidence: 89%

“…However, a growing number of studies have reported a failure of sham blinding during both high-(2mA) (O'Connell et al, 2012;Wallace et al, 2016) and lower-intensity (1-1.5mA) tDCS (Goldman et al, 2011;Kessler et al, 2012;Benwell et al, 2015;Greinacher et al, 2019;Turi et al, 2019). One potential source of these mixed results could stem from the method that is used to assess the success of sham blinding across studies.…”

Section: Introductionmentioning

confidence: 99%

“…We recently showed in Greinacher et al, (2019) that sham blinding was compromised during 1mA tDCS using a novel method of assessment. Participants undertook a simple, forced-choice reaction time task during 10min of 1mA active tDCS and a 20s 1mA sham protocol, based on Minarik et al, (2016).…”

Section: Introductionmentioning

confidence: 99%

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Is the “end-of-study guess” a valid measure of sham blinding during transcranial direct current stimulation?

Turner

Jackson

Learmonth

2020

Preprint

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Studies using transcranial direct current stimulation (tDCS) typically incorporate a fade-in, short-stimulation, fade-out sham (placebo) protocol, which is assumed to be indistinct from a 10-30min active protocol on the scalp. However, many studies report that participants can dissociate active stimulation from sham, even during low-intensity 1mA currents. We recently identified differences in the perception of an active (10min of 1mA) and a sham (20s of 1mA) protocol that lasted for 5 mins after the cessation of sham. In the present study we assessed whether delivery of a higher-intensity 2mA current would exacerbate these differences. Two protocols were delivered to 32 adults in a double-blinded, within-subjects design (active: 10min of 2mA, and sham: 20s of 2mA), with the anode over the left primary motor cortex and the cathode on the right forehead. Participants were asked "Is the stimulation on?" and "How sure are you?" at 30s intervals during and after stimulation. The differences between active and sham were more consistent and sustained during 2mA than during 1mA. We then quantified how well participants were able to track the presence and absence of stimulation (i.e. their sensitivity) during the experiment using cross-correlations. Current strength was a good classifier of sensitivity during active tDCS, but exhibited only moderate specificity during sham. The accuracy of the end-of-study guess was no better than chance at predicting sensitivity. Our results indicate that the traditional end-of-study guess poorly reflects the sensitivity of participants to stimulation, and may not be a valid method of assessing sham blinding.

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Section: Introductioncontrasting

confidence: 99%

Section: Introductioncontrasting

confidence: 54%

Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Is the “end-of-study guess” a valid measure of sham blinding during transcranial direct current stimulation?

Turner

Jackson

Learmonth

2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

Is the “end‐of‐study guess” a valid measure of sham blinding during transcranial direct current stimulation?

Turner

Jackson

Learmonth

2020

Eur J of Neuroscience

Self Cite

View full text Add to dashboard Cite

Studies using transcranial direct current stimulation (tDCS) typically incorporate a fade‐in, short‐stimulation, fade‐out sham (placebo) protocol, which is assumed to be indistinct from a 10–30 min active protocol on the scalp. However, many studies report that participants can dissociate active stimulation from sham, even during low‐intensity 1 mA currents. We recently identified differences in the perception of an active (10 min of 1 mA) and a sham (20 s of 1 mA) protocol that lasted for 5 min after the cessation of sham. In the present study we assessed whether delivery of a higher‐intensity 2 mA current would exacerbate these differences. Two protocols were delivered to 32 adults in a double‐blinded, within‐subjects design (active: 10 min of 2 mA, and sham: 20 s of 2 mA), with the anode over the left primary motor cortex and the cathode on the right forehead. Participants were asked “Is the stimulation on?” and “How sure are you?” at 30 s intervals during and after stimulation. The differences between active and sham were more consistent and sustained during 2 mA than during 1 mA. We then quantified how well participants were able to track the presence and absence of stimulation (i.e. their sensitivity) during the experiment using cross‐correlations. Current strength was a good classifier of sensitivity during active tDCS, but exhibited only moderate specificity during sham. The accuracy of the end‐of‐study guess was no better than chance at predicting sensitivity. Our results indicate that the traditional end‐of‐study guess poorly reflects the sensitivity of participants to stimulation, and may not be a valid method of assessing sham blinding.

show abstract

Author response for "The Time Course of Ineffective Sham Blinding During Low-Intensity (1mA) Transcranial Direct Current Stimulation"

Cited by 2 publications

References 0 publications

Is the “end-of-study guess” a valid measure of sham blinding during transcranial direct current stimulation?

Is the “end-of-study guess” a valid measure of sham blinding during transcranial direct current stimulation?

Is the “end‐of‐study guess” a valid measure of sham blinding during transcranial direct current stimulation?

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