tDCS, Moral Decision-Making, fMRI

Morality is the social rule about appropriateness of the behavior, containing concepts of justice, fairness, and rights. Previous studies suggested that the activation of right temporoparietal junction (rTPJ) should be involved in mental state reasoning in moral cognition. Implicit moral attitude, which reflects people's fundamental beliefs about right and wrong, could be assessed by implicit association test on moral scenarios (mIAT), as indicated by the D scores. According to our previous findings, we postulate that, during moral decision-making, the high D group would have less rTPJ involvement and the low D group would have more. Here we applied tDCS, a non-invasive neuromodulation technique, to modulate cortical excitability in rTPJ.

Based on our postulation, we divided participants into high D and low D group and hypothesized that tDCS over rTPJ would modulate the behavior depending on the group. The results revealed that, in aspect of mIAT, implicit moral attitude could be modulated differently depending on the group via tDCS over rTPJ. In addition, hemodynamic response within rTPJ showed a main effect of tDCS while carrying out the helping behavior. In conclusion, these findings indicated that tDCS over rTPJ could modulate the implicit moral attitude as well as the rTPJ activity during moral action.

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Key information

Conditions

Morality

Age range

20 year–30 year

Sex eligibility

All sexes

Study type

Observational

Who can participate

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

healthy volunteers, are all ethnic Chinese, right-handed, and aged between 20 to 30 years old

Exclusion criteria

any history of psychiatry or neurological disorders (e.g., dementia, seizures), head injury, and alcohol or substance abuse

Treatment and study plan

Transcranial Direct Current Stimulation

Device

In the present study, we applied DC Brain Stimulator Plus to stimulate right temporoparietal junction (rTPJ). The target electrode was placed over the location of rTPJ; on the other hand, the return electrode was placed over the left supraorbital area. That is, during anodal tDCS, the anode was placed over CP6, and the cathode was placed over left supraorbital area; conversely, during cathodal tDCS, the cathode was placed over CP6, and the anode was placed over left supraorbital area. For the active stimulation, which are anodal and cathodal tDCS, a constant current of 1 mA was delivered through 35 cm2 electrode for 20 minutes with fade-in and fade-out of 10 seconds, producing a current density of 0.029 mA/cm2. On the other hand, same fade-in, fade-out, and current density were applied for the sham stimulation, but the duration of current-delivering only last 35 seconds. Therefore, participants could feel the skin sensation but did not have the after-effects of tDCS.

Primary outcomes

Justice Sensitivity Inventory

Time frame: 10 minutes

Justice Sensitivity Inventory (JSI) is a self-report questionnaire which consists of four perspectives of justice sensitivity: victim, observer, beneficiary, and perpetrator (Schmitt, Baumert, Gollwitzer, & Maes, 2010; Schmitt, Gollwitzer, Maes, & Arbach, 2005). Each perspective contains ten descriptions, and participants would answer on a scale ranging from 1 (not at all) to 7 (exactly). Justice sensitivity reflects how people react to injustice and can be used to predict justice-related emotion and behavior (Baumert, Rothmund, Thomas, Gollwitzer, & Schmitt, 2013).
Morality Implicit Association Test

Time frame: 15 minutes

Implicit moral attitude was assessed by morality implicit association test (mIAT) in present study. The test was adapted from Implicit Association Test (IAT) developed by Greenwald and colleagues (1998). It measures the strength of the association 10 between target concepts and their associated attributes. In mIAT, target concepts were presented by morally good and morally bad clips, and attributes were presented by positive and negative words.
Moral Action Task

Time frame: 10 minutes

To verify the modulation of rTPJ activity via tDCS and to examine whether this modulation would alter people's moral behavior, participants would take the perspective of the active role while viewing moral scenarios in the MRI scanner.

Forty-five dynamic visual stimuli from previous research were validated and applied in the Moral Action Task. Each animation consists of three still images with the respective duration of 1000ms, 200ms, and 200ms. These animations contain three kinds of moral scenarios: (1) a person who is taking an action to physically harm one another (perpetrating behavior); (2) a person who is alleviating the physical pain which the other one is suffered (helping behavior); and (3) a person who is carrying out an action that irrelevant to the other one (neural behavior). Additionally, the protagonists in these scenarios were all acting without the presence of faces, and therefore the participants would have no emotional clues for these social interactions.

Secondary outcomes

Moral Evaluation: Rating of Moral Action Task

Time frame: 5 minutes

Outside the MRI scanner, participants carried out the Moral Action Task again. They were instructed to imagine themselves as the actor in the animation and pressed the button just like they really did the moral actions. Moreover, they were asked how much guilt or warm-glow after doing the action. The ratings were on a visual analog scale ranging from 1 to 7 points (Yoder & Decety, 2014).

Sponsors and collaborators

Lead sponsor

National Yang Ming Chiao Tung University Hospital

Other

Registry information

Official study title

The Role of Implicit Attitude in the tDCS Modulation on Moral Decision-Making

Important dates

Study start: 2016
Primary completion: 2019
Study completion: 2020
First posted: Dec 23, 2020
Registry last updated: Dec 23, 2020

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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