De facto masking and other measures to prevent contamination

Article · November 2012with5 Reads
DOI: 10.1016/j.jclinepi.2012.04.016 · Source: PubMed
    • However, O'Connell and colleagues' (2012) study, where participants were told that they would be given both stimulation conditions , suggests that blinding effectiveness is linked to participants' expectations about the tDCS experience, particularly when sham and active stimulation are given. O'Connell and colleagues (2012) recommended the use of de facto masking [42] in tDCS research, where participants are told that they will receive the active treatment condition throughout participation. Participants would therefore be more likely to anticipate some cutaneous sensations during stimulation, as appeared to be the case in the present study.
    [Show abstract] [Hide abstract] ABSTRACT: Background: tDCS studies typically find that: lowest levels of comfort occur at stimulation-onset; young adult participants experience less comfort than older participants; and participants' blinding seems effective at low current strengths. At 2 mA conflicting results have been reported, questioning the effectiveness of blinding in sham-controlled paradigms using higher current strengths. Investigator blinding is rarely reported. Objective: Using a protocol with 30 min of 2 mA stimulation we sought to: (a) investigate the level of perceived comfort in young and older adults, ranging in age from 19 to 29 years and 63 to 76 years, respectively; (b) test investigator and participant blinding; (c) assess comfort over a longer stimulation duration; (d) add to the literature on protocols using 2 mA current strength. Methods: A two-session experiment was conducted where sham and active stimulation were administered to the frontal cortex at the F8/FP1 sites in a within-subjects manner. Levels of perceived comfort were measured, using a visual analogue scale, at the start and end of stimulation in young and older adults. Post-stimulation, participants and investigators judged whether or not active stimulation was used. Results: Comfort scores were lower at stimulation onset in both age groups. Older adults reported: (i) more comfort than young participants overall; (ii) comparable levels of comfort in sham and active stimulation; (iii) significantly more comfort than the young participants during active stimulation. Stimulation mode was correctly identified above chance in the second of the two sessions; 65% of all participants correctly identified the stimulation mode, resulting in a statistical trend. Similarly, the experimenter correctly identified stimulation mode significantly above chance, with 62% of all investigator judgements correct across 120 judgements. Conclusions: Using 2 mA current strength over 30 minutes, tDCS stimulation comfort is lower at stimulation onset in young and older adults and, overall, lower for young participants. Investigators and participants may be able to identify active stimulation at above chance levels, although accuracy never exceeded 65% for either participants or the experimenter. Further research into blinding efficacy is recommended.
    Full-text · Article · Feb 2016
    • To examine this issue, we conducted a de facto (double-blinded) intervention [25] with two parallel groups (a brain training group and an active control group). The de facto intervention [25] was a kind of double-blinded intervention which participants and testers were kept blind to the experimental hypothesis. The participants were asked to perform each type of video game training (Brain Age or Tetris) over 4 weeks with at least 5 training days in each week.
    [Show abstract] [Hide abstract] ABSTRACT: Do brain training games work? The beneficial effects of brain training games are expected to transfer to other cognitive functions. Yet in all honesty, beneficial transfer effects of the commercial brain training games in young adults have little scientific basis. Here we investigated the impact of the brain training game (Brain Age) on a wide range of cognitive functions in young adults. We conducted a double-blind (de facto masking) randomized controlled trial using a popular brain training game (Brain Age) and a popular puzzle game (Tetris). Thirty-two volunteers were recruited through an advertisement in the local newspaper and randomly assigned to either of two game groups (Brain Age, Tetris). Participants in both the Brain Age and the Tetris groups played their game for about 15 minutes per day, at least 5 days per week, for 4 weeks. Measures of the cognitive functions were conducted before and after training. Measures of the cognitive functions fell into eight categories (fluid intelligence, executive function, working memory, short-term memory, attention, processing speed, visual ability, and reading ability). Our results showed that commercial brain training game improves executive functions, working memory, and processing speed in young adults. Moreover, the popular puzzle game can engender improvement attention and visuo-spatial ability compared to playing the brain training game. The present study showed the scientific evidence which the brain training game had the beneficial effects on cognitive functions (executive functions, working memory and processing speed) in the healthy young adults. Our results do not indicate that everyone should play brain training games. However, the commercial brain training game might be a simple and convenient means to improve some cognitive functions. We believe that our findings are highly relevant to applications in educational and clinical fields. UMIN Clinical Trial Registry 000005618.
    Full-text · Article · Feb 2013
    • Using intensities of 1 mA in future research may represent a more methodologically sound option, although it is plausible that reducing the intensity may reduce potential efficacy. Future studies of tDCS may benefit from other methods to optimise blinding, for example de facto masking [27], in which the treatment is not blinded but both treatments are presented as the active one. De facto masking might be more problematic if a non-stimulation sham is used that carries less credibility with participants but would seem very possible if the ''sham'' condition is active tDCS over a distinct brain area that is not hypothesized to elicit specific treatment effects.That we found inadequate blinding using a therapy widely held as blindable [8] raises the possibility that clinical trials of other therapies are vulnerable to similar problems.
    [Show abstract] [Hide abstract] ABSTRACT: Many double-blind clinical trials of transcranial direct current stimulation (tDCS) use stimulus intensities of 2 mA despite the fact that blinding has not been formally validated under these conditions. The aim of this study was to test the assumption that sham 2 mA tDCS achieves effective blinding. A randomised double blind crossover trial. 100 tDCS-naïve healthy volunteers were incorrectly advised that they there were taking part in a trial of tDCS on word memory. Participants attended for two separate sessions. In each session, they completed a word memory task, then received active or sham tDCS (order randomised) at 2 mA stimulation intensity for 20 minutes and then repeated the word memory task. They then judged whether they believed they had received active stimulation and rated their confidence in that judgement. The blinded assessor noted when red marks were observed at the electrode sites post-stimulation. tDCS at 2 mA was not effectively blinded. That is, participants correctly judged the stimulation condition greater than would be expected to by chance at both the first session (kappa level of agreement (κ) 0.28, 95% confidence interval (CI) 0.09 to 0.47 p = 0.005) and the second session (κ = 0.77, 95%CI 0.64 to 0.90), p = <0.001) indicating inadequate participant blinding. Redness at the reference electrode site was noticeable following active stimulation more than sham stimulation (session one, κ = 0.512, 95%CI 0.363 to 0.66, p<0.001; session two, κ = 0.677, 95%CI 0.534 to 0.82) indicating inadequate assessor blinding. Our results suggest that blinding in studies using tDCS at intensities of 2 mA is inadequate. Positive results from such studies should be interpreted with caution.
    Full-text · Article · Oct 2012
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  • Article · Mar 2013
  • [Show abstract] [Hide abstract] ABSTRACT: Bello, Moustgaard, and Hrobjartsson pointed out, correctly, that unmasking can lead to a host of problems, including cointervention bias, attrition bias, response bias, and observer bias. In fact unmasking can also lead to yet another bias, specifically selection bias. This is a crucial link, because the ability of perfect masking to preclude the possibility of selection bias means that the objective test for selection bias also doubles as an objective test for the success of masking.
    Article · Jun 2015