Effect Of High-definition tDCS Research Articles

Testing the effect of high-definition transcranial direct current stimulation of the insular cortex to modulate decision-making and executive control.

Previous neuroimaging evidence highlighted the role of the insular and dorsal anterior cingulate cortex (dACC) in conflict monitoring and decision-making, thus supporting the translational implications of targeting these regions in neuro-stimulation treatments for clinical purposes. Recent advancements of targeting and modeling procedures for high-definition tDCS (HD-tDCS) provided methodological support for the stimulation of otherwise challenging targets, and a previous study confirmed that cathodal HD-tDCS of the dACC modulates executive control and decision-making metrics in healthy individuals. On the other hand, evidence on the effect of stimulating the insula is still needed. We used a modeling/targeting procedure to investigate the effect of stimulating the posterior insula on Flanker and gambling tasks assessing, respectively, executive control and both loss and risk aversion in decision-making. HD-tDCS was applied through 6 small electrodes delivering anodal, cathodal or sham stimulation for 20 min in a within-subject offline design with three separate sessions. Bayesian statistical analyses on Flanker conflict effect, as well as loss and risk aversion, provided moderate evidence for the null model (i.e., absence of HD-tDCS modulation). These findings suggest that further research on the effect of HD-tDCS on different regions is required to define reliable targets for clinical applications. While modeling and targeting procedures for neuromodulation in clinical research could lead to innovative protocols for stand-alone treatment, or possibly in combination with cognitive training, assessing the effectiveness of insula stimulation might require sensitive metrics other than those investigated here.

Sensorimotor performance after high-definition transcranial direct current stimulation over the primary somatosensory or motor cortices in men versus women

The primary somatosensory (S1) cortex is a central structure in motor performance. However, transcranial direct current stimulation (tDCS) research aimed at improving motor performance usually targets the primary motor cortex (M1). Recently, sex was found to mediate tDCS response. Thus, we investigated whether tDCS with an anodal electrode placed over S1 improves motor performance and sensation perception in men versus women. Forty-five participants randomly received 15-min high-definition tDCS (HD-tDCS) at 1 mA to S1, M1, or sham stimulation. Reaching performance was tested before and immediately following stimulation. Two-point orientation discrimination (TPOD) of fingers and proprioception of a reaching movement were also tested. Although motor performance did not differ between groups, reaching reaction time improved in the M1 group men. Reaching movement time and endpoint error improved in women and men, respectively. Correct trials percentage for TPOD task was higher in the S1 compared to the M1 group in the posttest and improved only in the S1 group. Reaching movement time for the proprioception task improved, overall, and endpoint error did not change. Despite the reciprocal connections between S1 and M1, effects of active tDCS over S1 and M1 may specifically influence sensation perception and motor performance, respectively. Also, sex may mediate effects of HD-tDCS on motor performance.

The effect of transcranial direct current stimulation on the interplay between executive control, behavioral variability and mind wandering: A registered report

Mind wandering (MW) is a mental phenomenon humans experience daily. Yet, we lack a complete understanding of the neural basis of this pervasive mental state. Over the past decade there has been an increase in publications using transcranial direct current stimulation (tDCS) to modulate the propensity to mind wander, but findings are diverse, and a satisfactory conclusion is missing. Recently, Boayue et al. (2020) reported successful reduction of mind wandering using high-definition tDCS (HD-tDCS) over the dorsolateral prefrontal cortex, providing preliminary evidence for the efficacy of HD-tDCS in interfering with mind wandering. The current study is a high-powered, pre-registered direct replication attempt of the effect found by Boayue et al. (2020). In addition, we investigated whether the effects of HD-tDCS on mind wandering would be prolonged and assessed the underlying processes of mind wandering using electroencephalography (EEG) and pupillometry during a finger-tapping random sequence generation task that requires the use of executive resources. We failed to find any evidence of the original effect of reduced MW during and after stimulation. When combining our data with the data from Boayue et al. (2020), the original effect of reduced MW caused by HD-tDCS disappeared. In addition, we observed increased occipital alpha power as task duration increased and increased midfrontal theta power preceding response patterns signaling high executive function use. Finally, tonic and phasic pupil size decreased as task duration increased yet, phasic responses were increased, while tonic responses were reduced preceding reports of MW. Additionally phasic pupil size also showed a tendency to be increased during periods of high executive function use. Importantly, none of the EEG or pupil measures were modulated by HD-tDCS. We conclude that HD-tDCS over the dorsolateral prefrontal cortex does not affect MW propensity and its neural signatures. Furthermore, we recommend that previously reported effects of tDCS on mind wandering and other cognitive functions should only be accepted after a successful pre-registered replication.

Abstract #142: Effects of High Definition tDCS on Problem Solving Networks

Introduction: Idea generation stands at the heart of problem solving. People generate ideas by either having a sudden insight (implicit processing known as an "Aha! moment") or via a step-by-step analysis (explicit deliberation). Behavioral and neuroimaging studies demonstrated that these two ways of solving problems rely on distinct neural networks. Within the insight network, the right anterior temporal lobe has a critical role in the generation of novel associations and original ideas, whereas the left prefrontal cortex has a dominant role in explicit analytical deliberation. While progress has been made toward identifying the associated neural correlates of the idea generation phase during problem solving, its study thus far remains merely correlational. In the reported study, we adopt a causal approach by applying High Definition Transcranial Direct Current Stimulation (HD tDCS) to the brain sites crucial for problem solving, with the final aim of facilitating problem solving by modulating the two networks (insight and analysis).

Abstract #119: Polarity-dependent effects on postural control after High-definition Transcranial Direct Current Stimulation over the temporo-parietal junction

Introduction: Postural imbalance is a disorder involving complex integration of sensory, motor and cognitive systems, together with musculoskeletal components. A potential tool for the improving postural imbalance is transcranial direct current stimulation (tDCS). Targeting the temporo-parietal junction (TPJ), a critical hub for multisensory integration and processing, we recently showed that bipolar-balanced conventional tDCS can manipulate postural control and verticality perception. There is also evidence that high-definition tDCS (HD-tDCS) can achieve greater cortical stimulation focality and after-effects on motor cortical excitability than conventional tDCS. However, there is limited literature about the effects of HD-tDCS on postural control. Therefore, we aimed to investigate polarity- and intensity-dependent after-effects of HD-tDCS3x1 over the right TPJ on weight-bearing asymmetry (WBA) and head tilt in healthy adults.

The effect of high definition tDCS on cognitive control: A behavioral and fMRI study

The effect of high definition tDCS on cognitive control: A behavioral and fMRI study

P 235. Focal EEG effects of High Definition tDCS (HD-tDCS) detected by EEG photic driving

HD-tDCS using a 4 × 1-ring configuration has been proposed as an alternative to conventional tDCS, capable to restrict effective current to an area within the ring perimeter. Previously we observed that HD-tDCS stimulation achieves changes in TMS-evoked motor responses comparable to conventional tDCS. In order to investigate focality predicted by computational models, here we used EEG to detect neuronal changes both inside and outside stimulated region. On 15 normal subjects (5 males, 21–57 years), an EEG cap with special electrode holders arranged according to the 4 × 1-ring configuration was placed with the central electrode holder over central area of the left hemisphere (C3). The peripheral holders were spaced 5 cm radially around the central holder at the corners of a square. Monopolar EEG (linked earlobes reference, eyes closed) was recorded inside stimulation area in the central 4 × 1 (anode-An-C3), post-central (medial cathode-Ct-C3p), pre-central (between the anode and two anterior cathodes-Int-C3a) positions, outside the stimulation area in the left occipital lead (O1) and at the homologous right hemisphere points (C4a, C4, C4p and O2). EEG recordings were performed during intermittent photic stimulation (IPS) of fixed frequencies 3, 5, 10 and 21 Hz with 30s intervals between stimulation runs as well as during 3 min resting states before (1st) and after (2nd background) IPS sessions. After the initial EEG recording of 9.5–10 min duration, stimulation was delivered through a battery-driven constant current stimulator connected to a HD-tDCS adaptor device (Soterix Medical Inc., New York, NY). The current was delivered with a ramp-up time of 10s, held at 2 mA for 20 min, and then ramped down over 10 s. EEG was recorded 2–3 min after HD-tDCS. EEG amplitude spectra before and after HD-tDCS were compared for the background states in the 6 standard frequency bands and for the IPS states at all the EEG frequencies corresponding to those of IPS and its harmonics up to 30 Hz. A generalized increase in amplitude spectra after HD-tDCS was observed for the IPS of 3 Hz at the EEG frequencies of 3, 6, 9 and 24 Hz (fundamental frequency and 2nd, 3rd and 8th harmonics), this effect being significantly lower in the stimulation area of the left hemisphere (An-C3, Ct-C3p and Int-C3a) as compared to the homologous leads of the right hemisphere, with lower increase in the An-C3 as compared to the Ct-C3p at 6 and 24 Hz. No interhemispheric asymmetry was observed between occipital regions (O1 and O2). Similar increase was also observed for the 2nd background state in relation to the same state before HD-tDCS) in An-C3, Int-C3a, C4, and C4a in the theta band, in all the right hemisphere leads and in An-C3 and Ct-C3p in the alpha band with significant right-side prevalence, and in C4, C4a, and C4p in the beta-1 band. The earlier 1st background state after HD-tDCS did not show significant changes. These results are in accordance with HD-tDCS producing focal changes in brain function.