Modulation of perceived gratitude using Transcranial Direct Current Stimulation on the Medial Prefrontal Cortex

• Grant number: 23/04088-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: March 01, 2024
• End date: July 31, 2025
• Field of knowledge: Humanities - Psychology - Experimental Psychology
• Principal Investigator: Paulo Sérgio Boggio
• Grantee: Beatriz Bezerra de Souza
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Presbiteriana Mackenzie (UPM). Instituto Presbiteriano Mackenzie. São Paulo , SP, Brazil

Abstract

Gratitude is a complex emotion and a major psychological trait that relates to an individual's ability to feel thankful on a daily basis. Literature has shown that this emotion plays a significant role in subjective well-being levels, as well as in the construction of interpersonal relationships and moral decision-making, which makes it a positive, social, and moral emotion. In the last decade, the neural correlates of gratitude have been investigated using neuroimaging techniques, and the results of these studies have reported an increase in activity in the medial prefrontal cortex (mPFC) and its adjacent regions while participants engage in gratitude expression. However, these correlational studies leave an important gap in the literature on the neurobiological circuits of gratitude. In this scenario, techniques such as Transcranial Direct Current Stimulation (tDCS) appear, as they allow for the investigation of the neurobiology of gratitude in studies implying causality. Therefore, the proposed project outlines an experiment in which tDCS is used to neuromodulate the electrical activity of the medial prefrontal cortex while participants are subjected to an emotional vignette evaluation task. A low-intensity current (1.5 mA) will be applied to the mPFC for 20 minutes during the task. Following the International 10-20 System of Electroencephalography, the anode will be positioned between the eyebrows, and the cathode will be positioned at "Fz", using a 2cm by 2cm sponge (4cm²) and another 3cm by 4cm sponge (12 cm²), respectively, both soaked in saline solution. The study has a within-subject design, meaning that all participants will receive both active and placebo stimulation within a one-week interval. For the proposed task, participants will indicate which emotion, among sadness, joy, gratitude, and guilt, is more present while they read different vignettes with emotional content, as well as indicating the valence and intensity of each emotion.