White matter integrity predicts delay discounting behavior in 9- to 23-year-olds: a diffusion tensor imaging study

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Developmental Neuroscience

Background:

• Delay discounting, the devaluation of rewards with increasing delay, is crucial for understanding decision-making.
• The prefrontal cortex, undergoing significant development in adolescence and young adulthood, is implicated in this behavior.
• Individual differences in delay discounting suggest underlying neural variations.

Purpose of the Study:

• To investigate the relationship between white matter microstructure and individual differences in delay discounting.
• To explore how fractional anisotropy (FA) and mean diffusivity (MD) in white matter relate to discounting rates.
• To examine developmental and age-independent effects on this relationship.

Main Methods:

• A delay discounting task was administered to 79 healthy participants aged 9-23.
• Diffusion tensor imaging (DTI) was used to assess white matter integrity (FA and MD).
• Voxel-based regressions analyzed associations between discounting behavior and DTI metrics across whole-brain white matter.

Main Results:

• Less impulsive delay discounting was associated with higher FA and lower MD in specific white matter regions.
• These regions included tracts in the bilateral frontal and temporal lobes, such as the inferior longitudinal fasciculus and anterior thalamic radiation.
• FA generally increased and MD decreased with age, and some associations persisted after controlling for age.

Conclusions:

• White matter organization, particularly in frontal and temporal tracts, is associated with individual differences in delay discounting.
• These findings highlight both developmental and potentially age-independent influences of white matter microstructure on decision-making.
• The study provides neurobiological insights into the mechanisms underlying impulsive behavior.