Exploring the Role of the Prefrontal Cortex in Decision-Making

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.