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Fronto-striatal connectivity predicts patience
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anatomical MRI scans were reviewed and cleared by a radiologist from the radiology department of the Leiden University Medical Center (LUMC). No anomalous findings were reported. Participants received a financial reimbursement for their participation in a larger scale study (e.g., Braams et al. (2014a); Braams et al. (2014b); Peters et al. (2014a); Peters et al. (2014b); van Duijvenvoorde et al. (2016a)). The institutional review board of the LUMC approved the study and its procedures.
Intelligence quotient (IQ) was estimated with the subsets ‘similarities’ and ‘block design’ at T1 and the subsets ‘vocabulary’ and ‘picture completion’ at T2 of the Wechsler Intelligence Scale for Adults, third edition (WAIS-III) or the Wechsler Intelligence Scale for Children, third edition (WISC-III). Different subsets were used to prevent learning effects. The demographic characteristics of the sample are listed in Table 1. There was no significant correlation between estimated IQ and delay of gratification skills at T1 (r=.0195, p=.195) nor at T2 (r=.113, p=.119). Therefore, IQ was not included as covariate in the remaining analyses.
Table 1. Demographic characteristics of the sample (N=192, 48.4% male) at time point 1 and time point 2 [means (SD)]. IQ: intelligence quotient; AUC: area under the discounting curve (normalized); FS-tract: fronto-striatal tract; FA: fractional anisotropy; MD: mean diffusivity (in mm^2/s).
Age (years)
Age range Estimated IQ AUC (normalized) FS-tract FA FS-tract MD
Timepoint 1
14.32 (3.59)
8.01 - 24.55 110.78 (9.81) 0.42 (0.28)
0.329 (0.020) 0.00080 (0.00002)
Timepoint 2
16.28 (3.61)
9.92 - 26.62 108.23 (10.20) 0.47 (0.25)
0.333 (0.020) 0.00080 (0.00002)
Delay-Discounting Task
A computerized version of a hypothetical delay-discounting task described by Peper et al. (2013) was used, based on the paradigm explained by Richards et al. (1999). Subjects were asked to make a series of choices, between either a small, immediately available amount of money or €10 available after a delay (i.e., “What would you rather have: €2 right away or €10 in 30 days?”). Discounting was assessed at four delays (2, 30, 180 and 365 days later). Trials with different delays were presented in a mixed fashion. Furthermore, the task was adaptive: after the choice for the immediately available money, this amount was decreased on a next trial, whereas if the delayed money was preferred, the amount of immediately
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