Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly used to modulate neural activity in the living brain. In order to establish the neurophysiological, cognitive or clinical effects of tDCS,tDCS most studies compare the effects of active tDCS to those observed with a sham tDCS intervention. In most cases, sham tDCS consists in delivering an active stimulation for a few seconds to mimic the sensations observed with active tDCS and keep participants blind to the intervention. However, to date, sham-controlled tDCS studies yield inconsistent results, which might arise in part from sham inconsistencies. Indeed, a multiplicity of sham stimulation protocols is being used in the tDCS research field and might have different biological effects beyond the intended transient sensations. Here, we seek to enlighten the scientific community to this possible confounding factor in order to increase reproducibility of neurophysiological, cognitive and clinical tDCS studies.
Posts Tagged Reproducibility
[Abstract] Sham tDCS: A hidden source of variability? Reflections for further blinded, controlled trials
To evaluate construct validity and reproducibility of the Functional Gait Assessment (FGA) for measuring walking balance capacity in persons after stroke.
Fifty-two persons post-stroke (median (25% and 75% percentiles)) time post-stroke 6 (5–10) weeks) with independent walking ability (mean gait speed 1.1 ± .4 m/s).
Subjects completed a standardized FGA twice within one to eight days by the same investigator. Validity was evaluated by testing hypotheses on the association with two timed walking tests, Berg Balance Scale, and the mobility domain of the Stroke Impact Scale using correlation coefficients (r), and with Functional Ambulation Categories using the Kruskal–Wallis test. Reproducibility of FGA scores was assessed with intraclass correlation coefficient and standard error of measurement.
Subjects scored a median of 22 out of 30 points at the first FGA. Moderate to high significant correlations (r .61–.83) and significant differences in FGA median scores between the Functional Ambulation Categories were found. Eight hypotheses (80%) could be confirmed. Inter-rater, intra-rater, and test–retest reliability of the total scores were excellent. The standard error of measurement and minimal detectable change were 2 and 6 points, respectively. No relevant ceiling effect was observed.
[ARTICLE] Novel use of the Nintendo Wii board as a measure of reaction time: a study of reproducibility in older and younger adults – Full Text HTML
Reaction time (RT) has been associated with falls in older adults, but is not routinely tested in clinical practice. A simple, portable, inexpensive and reliable method for measuring RT is desirable for clinical settings. We therefore developed a custom software, which utilizes the portable and low-cost standard Nintendo Wii board (NWB) to record RT. The aims in the study were to (1) explore if the test could differentiate old and young adults, and (2) to study learning effects between test-sessions, and (3) to examine reproducibility.
A young (n = 25, age 20–35 years, mean BMI of 22.6) and an old (n = 25, age ≥65 years, mean BMI of 26.3) study-population were enrolled in this within- and between-day reproducibility study. A standard NWB was used along with the custom software to obtain RT from participants in milliseconds. A mixed effect model was initially used to explore systematic differences associated with age, and test-session. Reproducibility was then expressed by Intraclass Correlation Coefficients (ICC), Coefficient of Variance (CV), and Typical Error (TE).
The RT tests was able to differentiate the old group from the young group in both the upper extremity test (p < 0.001; −170.7 ms (95%CI −209.4;-132.0)) and the lower extremity test (p < 0.001; −224.3 ms (95%CI −274.6;-173.9)). Moreover, the mixed effect model showed no significant learning effect between sessions with exception of the lower extremity test between session one and three for the young group (−35,5 ms; 4.6 %; p = 0.02). A good within- and between-day reproducibility (ICC: 0.76-0.87; CV: 8.5-12.9; TE: 45.7-95.1 ms) was achieved for both the upper and lower extremity test with the fastest of three trials in both groups.
A low-cost and portable reaction test utilizing a standard Nintendo wii board showed good reproducibility, no or little systematic learning effects across test-sessions, and could differentiate between young and older adults in both upper and lower extremity tests.