There is equivocal support for the hypothesis that preference for later larger (LL) over sooner smaller (SS) monetary alternatives (e.g., $50 in four months over $30 today) is associated with functioning of the insula and the prefrontal cortex (especially the lateral PFC). In the present study, we re-examined overall neural correlates of choice using a procedure to minimize potential confounds between choice (which is necessarily not under experimental control) and valuation. In addition, we assessed whether choice-related brain activity is moderated by 1) overall level of delay discounting and 2) the degree of stochasticity in individuals' intertemporal choices. Twenty-one participants completed an individualized intertemporal choice task while brain activity was measured using functional Magnetic Resonance Imaging (fMRI). Across participants, LL choice was associated with activity in left dorsolateral prefrontal cortex (dlPFC), left insula/inferior frontal gyrus (IFG), frontal pole and the anterior cingulate cortex (ACC). Stochasticity positively moderated the LL>SS activity within the left insula and left IFG. Degree of discounting also interacted with choice related activity, but only outside the LL vs. SS main effect map (in the posterior cingulate cortex, and precentral/postcentral gyrus and left dlPFC). Main effect results are consistent with the notion that lateral prefrontal activity during intertemporal decisions bias selection in the direction of LL. Correlation findings indicate that choice related activity in the left insula and IFG is moderated by the stochasticity of intertemporal choices, and may reflect reduced "executive function" demands among highly consistent participants.
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