Delay and probability discounting: a longitudinal study of neural, cognitive, and emotional processes contributing to adolescent development.

Abstract

Adolescence is a time of rapid change in neurobehavioral characteristics, including emotional functioning, cognitive performance, and brain structure and function. The development of decision-making was examined in a group of adolescents (age 9-23) followed longitudinally over a two-year period. Delay and probability discounting tasks were used to assess decision-making. Change in discounting was examined in relation to baseline intelligence, working memory performance, personality factors, and internalizing and externalizing behaviors. In addition, contributions of brain structural features to the development of discounting behavior were analyzed. These included cortical thickness, white matter volume, subcortical volume, and diffusion tensor imaging (DTI) measures including fractional anisotropy and mean diffusivity. Delay discounting, but not probability discounting, showed significant maturation within individuals. Greater than expected maturation in delay discounting was seen in individuals with lower internalizing and externalizing psychopathology and higher positive emotionality. Brain structural factors predisposing toward greater than expected maturation included lower right frontal cortical thickness, larger cinguate and cuneate white matter volumes, larger hippocampal volumes, thicker parahippocampal gyrus cortical thickness, lower fractional anisotropy in the right temporal-parietal-occipital junction, and lower fractional anisotropy in the right amygdala/ pallidum/ hippocampus. Behavioral factors predisposing toward greater than expected change in probability discounting included female sex (for younger participants) and working memory performance (for males). Brain structural factors predisposing toward greater than expected change included cingulate white matter volume and higher mean diffusivity in the left parieto-occipital area. Findings are discussed in terms of implications for development of decision-making processes during adolescence.