Effects of Transcranial Direct Current Stimulation Over the Left VLPFC on Cognitive Reappraisal

Overview

This study aims to investigate the role of the left ventrolateral prefrontal cortex (VLPFC) on cognitive reappraisal, using the reinterpretation strategy. For this purpose, we will produce direct disturbance to the activity of this area through anodal and cathodal transcranial direct current stimulation during a reinterpretation task. A double-blind randomized sham-controlled trial will be conducted. 60 healthy volunteers will be allocated into three groups. Each group will receive one type of stimulation (anodal, cathodal or sham) while accomplishing a cognitive task on reinterpretation using images from the International Affective Pictures System (IAPS). The task consists in applying a given emotional regulation condition (downregulate, upregulate or maintain emotions) to a series of images and ranking the intensity of the emotional arousal felt after doing this procedure to each picture. The effects of tDCS on the subjective evaluation of emotional arousal after reinterpretation in each group will be compared.

60 healthy graduation and post-graduation at the Federal University of Pernambuco (UFPE) students will take part of the study. After providing written informed consent, the volunteers will respond to four online questionnaires, received by email: a sociodemographic questionnaire investigating eligibility conditions; the brazilian version of the Self-Reporting Questionnaire (SRQ-20) to screen for common psychiatric disorders; the brazilian self-report version of the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST) 3.0, to screen for drug-related disorders; and the brazilian version of the Emotion Regulation Questionnaire (ERQ) to evaluate individual profile of habitual use of emotion regulation strategies. They will be oriented to contact to researchers if they have any doubts. After filling the questionnaires, the volunteers will be contacted to be informed about eligibility. Individuals with previous history of epilepsy/ convulsions, brain tumors, neurosurgery, or with brain metallic implants or pacemakers, as well as in current use of psychotropic medication will be excluded from the study. The volunteers that score less than 5 point in SRQ-20 or more than 10 points for alcohol or more than 3 points for other substances in self-report ASSIST 3.0 will also be excluded from the sample. The selected volunteers will receive a training on the cognitive task. Firstly, they will receive a brief explanation and examples on cognitive reappraisal, the reinterpretation strategies and the instructions. Against the instruction MAINTAIN, they should simply look at the pictures and maintain their emotional experience, according to their initial interpretation of the presented situation. When facing the instruction DOWNREGULATE, they should look to the picture and imagine that the situation is better or will become better than initially perceived and when instructed to UPREGULATE, they should look to the picture and imagine that the situation is worse or will become worse than initially perceived. They will be presented on the computer screen to a series of 21 negative images preceded of a screen containing one of instructions (7 images for each instruction) and 7 neutral images preceded of a screen with the instruction maintain. The images will be presented randomly and they will be asked to generate strategies to each situation. They will be guided to provide adequate strategies to the received instructions and will receive a standardized example for each picture. After this phase, they will be presented to the same series of images in the same format as the experimental cognitive task. They will see 4 screens for each picture, following uninterruptedly. The fist will contain the strategy for 2 seconds, the second will present the picture for 8 seconds, the third will contain a visual scale from 1-7 to rank the intensity of the emotional arousal felt after applying the strategy to the picture (1=very weak; 7=very strong). They will be asked to press the correspondent number on a numerical keyboard into 5 seconds. The final screen will have the instruction RELAX for 3 seconds and they should wait and relax until the subsequent task initiate. The experiment will be conducted 3-5 days later. Before the experiment, the participant will respond to 2 questionnaires: the first will investigate behaviors that could influence the results of the experiment (sleep, psychostimulant substance intake) and the second will evaluate the current momentaneous status of the volunteer (humor, attention, fatigue). After a brief training of the cognitive task with 6 pictures, we will proceed to the electrodes montage. tDCS (1 mA) will be applied through a pair of saline-soaked surface sponge electrodes connected to a battery-driven constant current stimulator and positioned according to the 10-20 EEG system over the left VLPFC. A 4,5x4cm "active" electrode will be placed over the crossing point between T3-Fz and F7- Cz and a 12x5cm "return" electrode will be positioned over Fp2. The big return electrode will be used to attenuate the effects of stimulation over that region. The stimulation will start 4 minutes before the beginning of the cognitive task. The participants of the real stimulation groups will receive stimulation for 20 minutes, with 10 seconds ramp-up and down periods. In the sham group, the participants will receive the stimulation for 30 seconds. Measures of central tendency and dispersion (mean and standard deviation) for continuous variables and measures of frequency for the categorical variables will be used in the sample characterization. T-test for independent samples or qui-square will be used to verify comparability between groups for continuous and categorical variables, respectively. Shapiro-Wilk test will be used to evaluate normality. Repeated measures analyses of variance (ANOVAs) will be used to test for main effects and interaction with the within subjects factors regulation condition (downregulate, upregulate, negative maintain, neutral maintain) and the between-subjects factors (anodal, cathodal, sham stimulation) in case of normality. Paired t-test will be used for compare intra-group differences. T-test for independent samples will be conducted to compare inter-group differences. The sphericity will be verified with the Mauchly's test. Greenhouse-Geisser correction will be used when necessary. If normality is not verified, Friedman's test with post-hoc Wilcoxon test will be conducted to detect intra-group differences and post-hoc Mann-Whitney test will be conducted for inter-group differences. Two-tailed tests will be performed at 95% confidence interval for all analyses. Statistical analyses will be carried out using SPSS (Statistical Package for Social Sciences) 20.0 version for Windows (SPSS Inc, Chicago IL, USA).