TY - JOUR T1 - No Effect of 2mA Anodal tDCS Over the M1 on Performance and Practice Effect on Grooved Pegboard Test and Trail Making Test B JF - eneuro JO - eneuro DO - 10.1523/ENEURO.0072-14.2015 SP - ENEURO.0072-14.2015 AU - Asbjørn J. Fagerlund AU - Janita L. Freili AU - Therese L. Danielsen AU - Per M. Aslaksen Y1 - 2015/08/19 UR - http://www.eneuro.org/content/early/2015/08/19/ENEURO.0072-14.2015.abstract N2 - Previous studies suggest that transcranial direct current stimulation (tDCS) can facilitate motor performance and learning. In this double-blind experiment, 60 healthy human subjects (29 females) were randomized into 3 groups (active tDCS, sham tDCS, no-treatment control group) in order to investigate the effect of a 20-minute session of 2mA tDCS over the M1 contralateral to the dominant hand on practice effect and performance on the Grooved Pegboard Test (GPT) and Trail Making Test (TMT). Performance was operationalized as time to complete the tests before, during and after stimulation. Practice effect was termed as the difference in time to complete the tests from pre-test to post-test. Data on BMI, head circumference, sleep status, inter-electrode impedance, and caffeine and nicotine use were sampled to control for the influence of individual differences on the effect of tDCS. Adverse affects were registered using a standardized form. The results indicated no effect of tDCS on performance and practice effects on GPT and TMT. For all groups, BMI was a predictor for practice effect on TMT. In the active tDCS group, high caffeine intake and low impedance predicted practice effect on the GPT for the dominant hand. The present results suggest that impedance levels in tDCS studies should be routinely reported in future studies, as it might not only provide valuable information on the efficacy of the blinding conditions and participant discomfort, but also correlate with individual differences that are relevant to the outcome of the stimulation.Significance Statement: Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that can modulate neuronal activation thresholds. The capability to enhance or diminish cortical excitability has previously been consistently demonstrated in experiments, with no serious adverse effects. The effect of tDCS on behavioral outcomes, especially on healthy subjects, appears less consistent. We tested whether stimulation over the motor cortex affected performance and practice effect on two commonly employed neuropsychological test that requires fine motor skills, finger dexterity and psychomotor speed. The results indicated no effect of the stimulation on these outcomes. Uniquely for subjects that received active tDCS, caffeine intake and electrode impedance predicted increased practice effect. The authors suggests that impedance levels should be routinely reported in tDCS studies. ER -