Intertemporal choice behavior is constrained by brain structure in healthy participants and pathological gamblers

Abstract

The steepness of the delay discounting function shows considerable interindividual differences. Moreover, faster devaluation of future rewards has been consistently observed in pathological gamblers (PGs). Here, we asked whether variability in delay discounting is at least partially driven by differences in the anatomy of gray and white matter. For 40 healthy young subjects (study 1) as well as 15 PG and 15 age-matched healthy controls (HCs, study 2), the individual discounting parameter k was obtained. Based on 3D T1-weighted high-resolution magnetic resonance scans and diffusion tensor imaging, we performed voxel-based morphometry and tract-based spatial statistics, respectively, to examine the relation of gray matter volume (GMV) and white matter properties (as indicated by fractional anisotropy, FA) to k. Healthy groups from both studies showed a negative correlation between k and FA for the superior longitudinal fascicle and inferior longitudinal fascicle, whereas a positive correlation was found in the PG group for the inferior longitudinal fascicle and left inferior fronto-occipital fascicle. The latter also was significantly different between HC and PG in the group statistics (albeit on the right side), thus suggesting that this is a significant structure for the development of pathological gambling. GMV of the right frontal orbital cortex, left insular cortex and right lateral occipital cortex showed a positive correlation to k HC (studies 1 and 2) and PG, whereas a negative correlation was found for the left frontal pole in all three groups. Group comparison of GMV (study 2) revealed a decrease in PG for several cortical and subcortical areas.

Neuroanatomical foundations of delayed reward discounting decision making

“…Studies using with smaller sample sizes have reported relationships between DRD and GMV in different regions, such as prefrontal cortex, insular cortex, and striatum (Bjork et al, 2009; Mohammadi et al, 2015; Tschernegg et al, 2015; Wang et al, 2016). Here, the bilateral orbitofrontal cortex and left insula were associated with mAUC after FDR correction and others of these regions were represented among significant associations in the parcellation analysis (e.g., superior frontal gyrus, frontal pole), but did not survive multiple comparison correction.…”

“…This latter association was reported also in a subsequent study investigating only subcortical regions of the brain (Tschernegg et al, 2015). However, two other studies both found associations with the lateral prefrontal cortex, but not the medial prefrontal cortex (Bjork et al, 2009; Mohammadi et al, 2015). The largest study to date found DRD to be associated with GMV in the frontal pole, dorsolateral prefrontal cortex, medial orbitofrontal cortex, parahippocampal gyrus, striatum, temporal pole, precuneus, and precentral gyrus (Wang et al, 2016).…”

Right inferior frontal cortex activity correlates with tolcapone responsivity in problem and pathological gamblers

“…whether it implements an inhibitory “stop signal” itself or whether it is part of a larger network that provides a more general monitoring function (Hampshire and Sharp, 2015) – its activity has nonetheless previously been linked to addictive disorders. Loss of gray matter in closely adjacent regions has been found in PPG patients relative to control subjects (Mohammadi et al, 2015), and patients with a history of methamphetamine addiction similarly show selective atrophy within this brain area (Tabibnia et al, 2011). Moreover, in a large study of adolescents, activity within the RIFC during a stop signal task strongly differentiated those subjects who had used alcohol, nicotine, and at least one illicit substance from those who had not (Whelan et al, 2012).…”

Intertemporal Decision Making After Brain Injury: Amount-Dependent Steeper Discounting after Frontal Cortex Damage

“…The anterior insular cortex (AI) has been reported to be causally related to impulsive-compulsive decision making in rats (Belin-Rauscent et al, 2016). This is supported by results from human studies and the involvement of insula areas in decision making (Mohammadi et al, 2016). Specifically, damage to the AI, an important part of the cortical salience network (Menon & Uddin, 2010), may result in a pattern of behavior lacking discrimination between rewards of smaller and larger importance and consequently, not taking action aimed at obtaining a more valuable reward.…”

“…Furthermore, parts of the ventromedial prefrontal cortex, posterior cingulate cortex, and bilateral parietal cortex may be activated proportionally to the subjective value of the delayed reward (Massar, Libendinsky, Weiyan, Huettel, & Chee, 2015). In other studies, the negative correlation between the rate of discounting and gray matter volume in the insula area in the left hemisphere and the orbitofrontal cortex in the right hemisphere, and positive correlation between the gray matter of the frontal pole in the left hemisphere was observed (Mohammadi et al, 2016). This leads to the conclusion that the greater the volume in the insula area of the left hemisphere and the orbitofrontal cortex of the right hemisphere, the more steeply discounted the rewards.…”