Dataset Information

Adaptive current tDCS up to 4?mA.

ABSTRACT:

Background

Higher tDCS current may putatively enhance efficacy, with tolerability the perceived limiting factor.

Objective

We designed and validated electrodes and an adaptive controller to provide tDCS up to 4?mA, while managing tolerability. The adaptive 4?mA controller included incremental ramp up, impedance-based current limits, and a Relax-mode where current is transiently decreased. Relax-mode was automatically activated by self-report VAS-pain score >5 and in some conditions by a Relax-button available to participants.

Methods

In a parallel-group participant-blind design with 50 healthy subjects, we used specialized electrodes to administer 3 daily session of tDCS for 11?min, with a lexical decision task as a distractor, in 5 study conditions: adaptive 4?mA, adaptive 4?mA with Relax-button, adaptive 4?mA with historical-Relax-button, 2?mA, and sham. A tablet-based stimulator with a participant interface regularly queried VAS pain score and also limited current based on impedance and tolerability. An Abort-button provided in all conditions stopped stimulation. In the adaptive 4?mA with Relax-button and adaptive 4?mA with historical-Relax-button conditions, participants could trigger a Relax-mode ad libitum, in the latter case with incrementally longer current reductions. Primary outcome was the average current delivered during each session, VAS pain score, and adverse event questionnaires. Current delivered was analyzed either excluding or including dropouts who activated Abort (scored as 0 current).

Results

There were two dropouts each in the adaptive 4?mA and sham conditions. Resistance based current attenuation was rarely activated, with few automatic VAS pain score triggered relax-modes. In conditions with Relax-button option, there were significant activations often irrespective of VAS pain score. Including dropouts, current across conditions were significantly different from each other with maximum current delivered during adaptive 4?mA with Relax-button. Excluding dropouts, maximum current was delivered with adaptive 4?mA. VAS pain score and adverse events for the sham was only significantly lower than the adaptive 4?mA with Relax-button and adaptive 4?mA with historical-Relax-button. There was no difference in VAS pain score or adverse events between 2?mA and adaptive 4?mA.

Conclusions

Provided specific electrodes and controllers, adaptive 4?mA tDCS is tolerated and effectively blinded, with acceptability likely higher in a clinical population and absence of regular querying. Indeed, presenting participants with overt controls increases rumination on sensation.

SUBMITTER: Khadka N

PROVIDER: S-EPMC6888879 | biostudies-literature | 2020 Jan - Feb

REPOSITORIES: biostudies-literature

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Publications

Adaptive current tDCS up to 4 mA.

Khadka Niranjan N Borges Helen H Paneri Bhaskar B Kaufman Trynia T Nassis Electra E Zannou Adantchede L AL Shin Yungjae Y Choi Hyeongseob H Kim Seonghoon S Lee Kiwon K Bikson Marom M

Brain stimulation 20190805 1

<h4>Background</h4>Higher tDCS current may putatively enhance efficacy, with tolerability the perceived limiting factor.<h4>Objective</h4>We designed and validated electrodes and an adaptive controller to provide tDCS up to 4 mA, while managing tolerability. The adaptive 4 mA controller included incremental ramp up, impedance-based current limits, and a Relax-mode where current is transiently decreased. Relax-mode was automatically activated by self-report VAS-pain score >5 and in some condition ...[more]

PMID: 31427272

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Project description:BackgroundtDCS studies typically find that: lowest levels of comfort occur at stimulation-onset; young adult participants experience less comfort than older participants; and participants' blinding seems effective at low current strengths. At 2 mA conflicting results have been reported, questioning the effectiveness of blinding in sham-controlled paradigms using higher current strengths. Investigator blinding is rarely reported.ObjectiveUsing a protocol with 30 min of 2 mA stimulation we sought to: (a) investigate the level of perceived comfort in young and older adults, ranging in age from 19 to 29 years and 63 to 76 years, respectively; (b) test investigator and participant blinding; (c) assess comfort over a longer stimulation duration; (d) add to the literature on protocols using 2 mA current strength.MethodsA two-session experiment was conducted where sham and active stimulation were administered to the frontal cortex at the F8/FP1 sites in a within-subjects manner. Levels of perceived comfort were measured, using a visual analogue scale, at the start and end of stimulation in young and older adults. Post-stimulation, participants and investigators judged whether or not active stimulation was used.ResultsComfort scores were lower at stimulation onset in both age groups. Older adults reported: (i) more comfort than young participants overall; (ii) comparable levels of comfort in sham and active stimulation; (iii) significantly more comfort than the young participants during active stimulation. Stimulation mode was correctly identified above chance in the second of the two sessions; 65% of all participants correctly identified the stimulation mode, resulting in a statistical trend. Similarly, the experimenter correctly identified stimulation mode significantly above chance, with 62% of all investigator judgements correct across 120 judgements.ConclusionsUsing 2 mA current strength over 30 minutes, tDCS stimulation comfort is lower at stimulation onset in young and older adults and, overall, lower for young participants. Investigators and participants may be able to identify active stimulation at above chance levels, although accuracy never exceeded 65% for either participants or the experimenter. Further research into blinding efficacy is recommended.

Project description:Although posttraumatic stress disorder (PTSD; DSM-V 309.82) and anxiety disorders (DSM-V 300.xx) are widely spread mental disorders, the effectiveness of their therapy is still unsatisfying. Non-invasive brain-stimulation techniques like transcranial direct current stimulation (tDCS) might be an option to improve extinction learning, which is a main functional factor of exposure-based therapy for anxiety disorders. To examine this hypothesis, we used a fear conditioning paradigm with female faces as conditioned stimuli (CS) and a 95-dB female scream as unconditioned stimulus (UCS). We aimed to perform a tDCS of the ventromedial prefrontal cortex (vmPFC), which is mainly involved in the control of extinction-processes. Therefore, we applied two 4 × 4 cm electrodes approximately at the EEG-positions F7 and F8 and used a direct current of 1.5 mA. The 20-min stimulation was started during a 10-min break between acquisition and extinction and went on overall extinction-trials. The healthy participants were randomly assigned in two double-blinded process into two sham stimulation and two verum stimulation groups with opposite current flow directions. To measure the fear reactions, we used skin conductance responses (SCR) and subjective ratings. We performed a generalized estimating equations model for the SCR to assess the impact of tDCS and current flow direction on extinction processes for all subjects that showed a successful conditioning (N = 84). The results indicate that tDCS accelerates early extinction processes with a significantly faster loss of CS+/CS- discrimination. The discrimination loss was driven by a significant decrease in reaction toward the CS+ as well as an increase in reaction toward the CS- in the tDCS verum groups, whereas the sham groups showed no significant reaction changes during this period. Therefore, we assume that tDCS of the vmPFC can be used to enhance early extinction processes successfully. But before it should be tested in a clinical context further investigation is needed to assess the reason for the reaction increase on CS-. If this negative side effect can be avoided, tDCS may be a tool to improve exposure-based anxiety therapies.

Dataset Information

Adaptive current tDCS up to 4?mA.

Background

Objective

Methods

Results

Conclusions

Publications

Adaptive current tDCS up to 4 mA.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Dataset Information

Adaptive current tDCS up to 4?mA.

Background

Objective

Methods

Results

Conclusions

Publications

Adaptive current tDCS up to 4 mA.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Adaptive current tDCS up to 4 mA.