Investigating the neural sources of decision urgency in typically developing adolescents

Details

Supervisors

Duque, Julie

Faculty

Faculté de pharmacie et des sciences biomédicales

Degree label

Master [120] en sciences biomédicales, à finalité approfondie

Abstract

enDecision-making is a fundamental aspect of our behavior. Typically, a decision occurs when the accumulation of information in favor of one choice reaches a neural threshold. However, a recent line of research suggests that an urgency signal, which increases over time, also contributes to decision-making. Traditionally viewed as a unitary signal, urgency may be modulated by multiple factors. In this master’s thesis, we investigated two key factors that may influence urgency: inhibitory control, hypothesized to reduce urgency (via the hyperdirect pathway connecting the pre-supplementary motor area to the subthalamic nucleus), and motivation by reward, expected to increase it (via the dopaminergic pathways of the basal ganglia). To examine these factors, adolescents are a particularly relevant population to study due to their immature inhibitory control and increased sensitivity to reward. These behavioral traits are thought to result from the ongoing maturation of white matter pathways and evolving functional connectivity between brain regions during adolescence. Based on this, we hypothesized that adolescents would show an increased urgency due to their reduced inhibitory control and heightened reward sensitivity, driven by the structural and functional developmental activity of the hyperdirect and dopaminergic basal ganglia pathways. To test this hypothesis, we recruited 82 participants: 41 adolescents and 41 adults. All participants performed a visuomotor task allowing us to study urgency dynamics, the Tokens Task, which was modified to manipulate inhibitory control and motivation by reward. Participants also underwent Magnetic Resonance Imaging (MRI) to assess white matter microstructure and resting-state functional connectivity within the hyperdirect pathway and the dopaminergic pathways. Behavioral measures derived from the task, such as urgency, will then be correlated with these structural and functional measures. Our results show that motivation by reward increases urgency, similarly in adolescents and adults. Structural maturation of the dopaminergic pathways was not associated with this urgency modulation. In contrast, adolescents and adults showed different urgency modulation in response to inhibitory control and interestingly, these differences were related to the maturation of the hyperdirect pathway. These findings support the hypothesis that adolescents show a greater urgency partly due to immature inhibitory control.