Fig. 1: Study objectives and paradigm description.

Study objectives are numbered from 1 to 3. Objective 1 was to identify potential markers of higher impatience for reward in bvFTD patients (compared to controls). For this purpose, we firstly tested the effect of bvFTD on two outcomes of intertemporal choice tasks for money and food rewards: the discount rate and sensitivity to larger later reward amounts. The visual presentation of the two ITC tasks used to assess delay discounting in the study shows an example of trial with monetary rewards on the left and with food rewards (chocolate) on the right. Objective 2 was to further test discount rates and sensitivities to larger later reward as markers of higher impatience for reward in bvFTD by showing their links with impulsivity-related symptoms among patients: (1) inhibition deficits (measured by Hayling test error score); (2) lower executive functions (assessed by the Frontal Assessment Battery) and 3) eating behaviour changes such as binge eating and preference for sweet foods (measured by the Eating Behaviour Inventory). Objective 3 was to investigate the brain regions in which atrophy may cause higher impatience for reward in bvFTD patients (compared to controls). We used a whole-brain mediation approach applied to participants’ grey matter density maps (T1-weighted images pre-processed for VBM) to identify regions mediating the increase in discount rate and the decrease in sensitivity to larger later rewards in bvFTD (compared to controls). The coin and chocolate illustrations are from a public database (https://publicdomainvectors.org/) and are under a CC0 Public Domain Dedication license.