Exploring the Role of the Prefrontal Cortex in Decision-Making

Overview

The goal of this study is to examine whether high-definition transcranial direct current stimulation (HD-tDCS) can influence decision-making for emotionally valenced content in younger and older adults, with or without major depression. The main questions are: In healthy adults, does brain stimulation modulate how people respond to emotionally valenced content during a decision-making task? What happens in the brain during modulation? Do these effects differ between younger and older adults? In adults with depression, does brain stimulation help shift attention towards positive content during the task? What happens in the brain? Are these effects moderated by age (younger vs. older adults)? The investigators will compare participants who receive real stimulation to those who receive sham (placebo) stimulation. Participants will: Receive high-definition transcranial direct current stimulation (HD-tDCS) of the dorsolateral prefrontal cortex (DLPFC) Perform a decision-making task involving emotionally valenced words Complete the task while undergoing a brain scan using ultra-high field 7 Tesla magnetic resonance imaging (MRI) to measure brain activity

This study investigates whether non-invasive brain stimulation influences decision-making in four groups: younger adults (20-40 years) and older adults (60-75 years), healthy or with mild to moderate major depression. Participants with personality disorders or psychosis will be excluded. The study builds on evidence that the dorsolateral prefrontal cortex (DLPFC) plays a key role in evaluating emotionally-valenced material and decision-making. The investigators will examine whether modulation of this region through high-definition transcranial direct current stimulation (HD-tDCS) affects responses to emotionally valenced information. Stimulation will be administered differently across groups based on theoretical models of hemispheric function in mood regulation. To explore the effect of stimulation at neurotransmitter level, the investigators will use ultra-high field 7 Tesla magnetic resonance spectroscopy (MRS) to measure Gamma-aminobutyric acid (GABA) / Glutamate concentrations in regions of interest at baseline and after stimulation. This allows to examine whether changes in inhibitory/excitatory neurotransmitters are linked to altered emotional processing and decision making. By combining brain stimulation, ultra-high field neuroimaging, and spectroscopy, this study examines how changes in brain network activity and neurotransmitter levels relate to decision-making in health and disease. The inclusion of both younger and older adults allows the investigators to explore age-related differences in these processes. This project aims to provide mechanistic insights into decision-making in health and disease and to support the development of targeted neuromodulation therapies that could modulate emotional processing.