PMC

The hyperbolic function derived by fitting the mean indifference point of all subjects across each delay value (2s, 4s, 16s, 32s, and 64s). Indifference points represent the mid-point at which the subjects switched from choosing the delayed reward to the immediate reward.

ROI based analysis: bilateral caudate and anterior insula exhibited significantly greater activation (p < 0.05, corrected; V > 256 μL) during both immediate (A) and delayed (B) decisions (selecting an option) as compared to baseline.

ROI based analysis (p < 0.05, corrected; V > 256 μL): A) Ventroanterior striatum exhibited significantly greater activation when subjects chose the immediate option than when they chose the delayed option (contrast: delayed vs. immediate option). B) The ventroanterior striatum displayed significantly greater activation when collecting the delayed as opposed to the immediate reward (contrast: delayed vs. immediate collection).

Whole brain analysis (p < 0.05, corrected; V > 704μL): (A) the percent of immediate options chosen by the subject was positively correlated with activity in the right inferior frontal gyrus during selection of the immediate option. (B) a negative correlation was found between the percent of immediate options chosen by the subject and activity in the right posterior temporal gyrus and the inferior frontal gyrus during selection of the delayed option.

Subjects were repeatedly presented with a nearly immediate (right side) and a delayed reward option (left side) and instructed to choose one of the two by pressing a corresponding button on a response box. The immediate option consisted of a reward value of either $0.01, $0.06, $0.12, $0.18, or $0.24 available after a 2 second waiting period. The delayed option had a constant reward value of $0.24, but the waiting period varied between 4, 16, 32, and 64 seconds. A running total of the subjects earning was shown at all times in the upper center portion of the display screen.