Spreading Effect of tDCS in Individuals with Attention-Deficit/Hyperactivity Disorder as Shown by Functional Cortical Networks: A Randomized, Double-Blind, Sham-Controlled Trial

Abstract

BackgroundTranscranial direct current stimulation (tDCS) is known to modulate spontaneous neural network excitability. The cognitive improvement observed in previous trials raises the potential of this technique as a possible therapeutic tool for use in attention-deficit/hyperactivity disorder (ADHD) population. However, to explore the potential of this technique as a treatment approach, the functional parameters of brain connectivity and the extent of its effects need to be more fully investigated.ObjectiveThe aim of this study was to investigate a functional cortical network (FCN) model based on electroencephalographic activity for studying the dynamic patterns of brain connectivity modulated by tDCS and the distribution of its effects in individuals with ADHD.MethodsSixty ADHD patients participated in a parallel, randomized, double-blind, sham-controlled trial. Individuals underwent a single session of sham or anodal tDCS at 1 mA of current intensity over the left dorsolateral prefrontal cortex for 20 min. The acute effects of stimulation on brain connectivity were assessed using the FCN model based on electroencephalography activity.ResultsComparing the weighted node degree within groups prior to and following the intervention, a statistically significant difference was found in the electrodes located on the target and correlated areas in the active group (p < 0.05), while no statistically significant results were found in the sham group (p ≥ 0.05; paired-sample Wilcoxon signed-rank test).ConclusionAnodal tDCS increased functional brain connectivity in individuals with ADHD compared to data recorded in the baseline resting state. In addition, although some studies have suggested that the effects of tDCS are selective, the present findings show that its modulatory activity spreads. Further studies need to be performed to investigate the dynamic patterns and physiological mechanisms underlying the modulatory effects of tDCS.Trial Registration NCT01968512.

Transcranial Direct Current Stimulation Facilitates Associative Learning and Alters Functional Connectivity in the Primate Brain

“…This protocol generates the same somatosensory percepts as the active condition but passes far less charge into the brain. Since blinded human subjects are typically unable to report whether they received active or sham stimulation [18,32], this tDCS versus sham comparison is currently the gold standard for human neurostimulation research [33]. Figure 1A shows representative signals from electrodes in PFC (left) and ITC (right).…”

“…Instead, some studies have suggested that tDCS might alter neural excitability [12,13], brain oscillations [14,15], or functional connectivity [2,16]. The few studies that have recorded neuronal data along with tDCS used small animals and invasive stimulation paradigms that cannot be applied to humans (e.g., stimulating through screws driven deep into the skull) [17][18][19][20]. Thus, fundamental questions about the nature and efficacy of tDCS remain.…”

Applications of transcranial direct current stimulation in children and pediatrics

“…Furthermore, interhemispheric disconnectivity of the frontal lobes has been described (Robbie et al, 2016). tDCS could be a tool to modulate these EEG derivatives of cortical arousal and connectivity via alteration of respective cortical oscillatory activity and thereby improve performance (Cosmo et al, 2015). For cognitive deficits, impaired behavioral inhibition in children with ADHD (10-14 years) was monitored via a go/ no-go reaction time task the day after application of slow oscillating (0.75 Hz of frequency) anodal tDCS bilaterally over F3-F4 (reference electrodes placed over the ipsilateral mastoids) during non-REM sleep (Munz et al, 2015).…”

Transcranial Direct Current Stimulation for Treatment of ADHD: A Review of the Mechanisms of Action

“…Different preclinical and clinical studies have investigated the therapeutic efficacy of tDCS in improving the symptoms of ADHD [19,20,23,24] . Different sites of stimulation have been studied with different stimulation parameters including intensity, duration, and a number of sessions.…”

“…During recent years, different brain stimulation and modulation techniques have been developed for different neuropsychiatric disorders [13][14][15]. Among the brain modulation techniques, transcranial direct current stimulation (tDCS) has shown interesting potentials as an alternative or adjunctive treatment for different psychiatric disorders including ADHD [12,[16][17][18][19][20][21][22][23]. TDCS is a noninvasive, lowcost, easy to use technique where a week direct current is delivered to the scalp through a pair of electrode, through which the flowing current changes the cortical excitability of the neurons and ultimately alters behavior [24].…”