Null tDCS Effects in a Sustained Attention Task: The Modulating Role of Learning

Abstract

The purpose of this study was to investigate sustained attention through modulation of the fronto-cerebral network with transcranial direct current stimulation (tDCS) in adults with attention-deficit/hyperactivity disorder (ADHD) and control participants. Thirty-seven participants (21 with ADHD) underwent three separate sessions (baseline, active tDCS, and sham) and performed the MOXO Continuous Performance Test (CPT). We applied double anodal stimulation of 1.8 mA tDCS for 20 min over the left and right dorsolateral prefrontal cortex (DLPFC), with the cathode over the cerebellum. Baseline session revealed significant differences between ADHD and control participants in the MOXO-CPT attention and hyperactivity scores, validating the MOXO as a diagnostic tool. However, there were no tDCS effects in most MOXO-CPT measures, except hyperactivity, due to a significant learning effect. We conclude that learning and repetition effects in cognitive tasks need to be considered when designing within-subjects tDCS experiments, as there are natural improvements between sessions that conceal potential stimulation effects.

Asymmetric Contributions of the Fronto-Parietal Network to Emotional Conflict in the Word–Face Interference Task

“…However, they are less unusual than one may think. In fact, they were observed by Jacoby and Lavidor [82] during a sustained attention task, by Hammer, Mohammadi, Schmicker, Saliger, and Münte [83], who observed decreased memory performance in a cathodal condition compared to sham tDCS but only after learning and by Zaehle et al [84], who suggested that performance enhancement due to task repetition might be hampered by cathodal stimulation over the lDLPFC. Our findings of reduced interference from angry distractor-faces indicate the other side of the coin: namely, that performance enhancement due to task repetition is potentiated by anodal stimulation of the lDLPFC/cathodal rPPC.…”

Noninvasive brain stimulation in children and adults with attention-deficit/hyperactivity disorder: a systematic review and meta-analysis

“…Finally, we used jackknife sensitivity analyses (i.e., repeating the same analysis and excluding a different study each time) to establish the replicability of findings. To improve homogeneity, we carried out additional sensitivity analyses that excluded studies with overlapping samples, [60][61][62][63] or studies with methods that deviated from the majority of studies, such as those including community participants with high ADHD symptoms on validated ADHD ratings scales but without a clinical ADHD diagnosis; 43,64 those including adult samples with ADHD; 42,65,66 those targeting the right inferior frontal cortex (IFC); 43,67 those reporting change scores (i.e., post minus pre differences) rather than post scores only; 66 those using multi-stimulation sessions; [60][61][62]65 those with effect sizes based on working memory or WCST tasks; 61,68 or those using parallel rather than crossover designs. 62,66,67 Lastly, given that effect-size estimates might be inflated in studies with a high risk of bias, we conducted meta-regression analyses to compare the effect sizes of studies with high versus low or unclear risk of bias for each risk of bias domain (i.e., selection bias, performance bias, detection bias, attrition bias and other biases).…”

“…Cosmo et al 66 None reported Jacoby et al 42 Not tested, but authors reported that stimulation was well tolerated and no side effects were reported Munz et al 60 Not tested, but no side effects were reported Nejati et al 68 Reports of mild itching or tingling under electrodes Paz et al 73 Allenby et al 65 Bloch et al 71 rTMS studies tDCS studies…”

“…39,40 A recent meta-analysis of 10 tDCS studies in ADHD (n = 201) found that predominantly anodal tDCS of the dlPFC led to a significant but small improvement in measures of inhibitory control (Hedges' g = 0.12, 95% confidence interval [CI] 0.01-0.24), and to a significant but moderate improvement in reaction times in n-back tasks in a smaller meta-analysis of 7 effect sizes derived from 3 studies (Hedges' g = 0.66, 95% CI 0.17-1.25). 41 However, effect size estimates may have been inflated, because 2 studies reporting mostly null effects were not included; 42,43 multiple dependent effects were clustered in the meta-analyses, unduly reducing variation between effect sizes and overestimating statistical significance; 44,45 and the analysis of inhibitory control measures included noninhibitory measures, such as inattention (e.g., omission errors), processing speed (e.g., reaction times to go trials) and reaction time variability, calling into question the specificity of the positive tDCS effects to the domain of inhibitory control.…”

Implications of Unconnected Micro, Molecular, and Molar Level Research in Psychology: The Case of Executive Functions, Self-Regulation, and External Regulation

“…This level of analysis, therefore, is optimal for explaining disorders based on neurological problems and brain injuries. There has been prolific evidence in recent years of the important role of the frontal cortex and the functional role of “executive functions” for predicting performance (Gathercole and Pickering, 2000a, b; Blair and Razza, 2007; Bull et al, 2008; Cleary and Chen, 2009; Agostino et al, 2010; Molfese et al, 2010; Monette et al, 2011; De los Ángeles, 2012; Diamond, 2012, 2013; Ramírez, 2014; Arán and López, 2016; Diamond and Ling, 2016; Cid-Sillero et al, 2018; Díez and Bausela, 2018; Follmer, 2018; Jacoby and Lavidor, 2018). An impairment in executive functioning has also been related to antisocial and delinquent behaviors (De Brito and Hodgind, 2009; Pera-Guardiola et al, 2016; Gil-Fenoy et al, 2018).…”