Cortico-striatal connectivity relates to the malleability of intertemporal decisions

895 

Abstract Submission 

Yueting Su¹, Xinyu Liang¹, Deniz Vatansever¹

¹Fudan University, Shanghai, Shanghai

Yueting Su  
Fudan University
Shanghai, Shanghai

Xinyu Liang  
Fudan University
Shanghai, Shanghai

Deniz Vatansever  
Fudan University
Shanghai, Shanghai

Human decisions often involve the evaluation of outcomes at multiple timescales. Individual variation in such intertemporal decisions is suggested to rely on a cortico-striatal circuitry, which is predictive of both impulsivity and mental health symptoms [1]. However, emerging evidence also indicate a level of malleability of intertemporal choices via behavioural nudges [2], which may be reflected by interindividual differences in the macro-scale connectivity architecture of the human brain. Here, introducing pre-selected "default choice" options in an intertemporal choice paradigm, we first identify striatal regions engaged in intertemporal decisions and computationally model participants' propensity to be influenced by behavioural nudges. In a subsequent connectivity analysis at rest, we provide brain-behaviour links between individual's decision bias, connectivity profiles and ADHD symptoms.

Using an HCP-style data acquisition protocol [3], a group of 41 healthy participants (mean = 24.25 years, SD = 2.49, F/M ratio = 29/12) were scanned at 3T MRI, both at rest (AP/PA) and while performing two runs of a Nudged-Intertemporal Choice (NIT) paradigm (Fig. 1a). In the NIT task, participants were asked to make intertemporal monetary decisions between an immediate and a delayed reward option across 96 trials that included both easy and hard options. Importantly, a proportion of choices were nudged using a pre-selected "default choice" option. To assess the influence of default nudges on each individual's decision starting point (i.e. bias "z" parameter), task response data was modelled with a hierarchical Bayesian parameter estimation of the drift diffusion model [4]. Imaging data was minimally preprocessed using Qunex containerized versions of the HCP preprocessing pipelines [5]. The task fMRI data was then statistically modelled using FSL FEAT routines to contrast Intertemporal Choice versus Control conditions, corrected for individual discount rates. Significant regions of interest from the NIT task fMRI results were used as seeds to quantify whole-brain functional connectivity via Pearson correlation. Adult ADHD Self-Report Scale (ASRS) [6] symptom scores, NIT task decision bias scores and connectivity estimates were used to assess brain-behaviour relationships. Statistical significance was estimated using non-parametric permutation testing via PALM (FDRp < .05).

Behaviourally, computational modelling of NIT task responses indicated a significant effect of default nudges on the decision starting point, specifically within hard trials (p < .05) (Fig. 1b). At the neural level, the contrast of ITC > Control, revealed greater activity centered on a set of brain regions commonly associated with monetary decisions including the bilateral ventral striatum, medial prefrontal, orbitofrontal, and anterior cingulate cortices (Fig. 2a). Activated regions in the bilateral ventral striatum (VS) were selected as seed regions of interest in a subsequent resting state functional connectivity analysis, to reveal the neural circuitry associated with intertemporal decisions. The analysis showed strong VS connectivity with regions within the default mode and frontoparietal control networks (Fig. 2b). Notably, connectivity of VS to the right medial prefrontal cortex (mPFC), a region within the default mode network, positively correlated with decision bias (r = 0.59, p < .001) and was negatively linked to ASRS Inattentive sub-scores (r = .36, p = .02) (Fig. 2c).

Collectively, our results indicate that default nudges constitute an effective behavioral strategy to alter individual's intertemporal decisions. In this context, a ventral striatal – medial prefrontal cortex circuitry is highlighted to play a vital role, providing mechanistic insight on the behavioral nudging of intertemporal decisions and revealing a potential neural target for future interventions in the treatment of impulsivity disorders.

Reward and Punishment ²

Decision Making ¹

Cognition

FUNCTIONAL MRI

Other - Intertemporal Choice; Behavioural Nudges