Figure 2.
Group differences in reward processing in the right VS.
A) Effect of absolute reward magnitude processing. Adults compared to adolescents demonstrated a more linear increase in anticipatory reward activation as a function of absolute reward magnitude at the point of peak activation (6 seconds post-stimulus onset; p = .02). B) Relative reward activity in VS to $1 reward. Based on paired t-tests for each age group, results showed that adults (p = .007) but not adolescents (p = .34) demonstrated significant differences in VS activity at 6 seconds post-stimulus onset to the $1 reward depending on the relative context.
Figure 1.
Behavioral performance on the modified MID Task.
As described in greater detail in the text, adults and adolescents were faster and more accurate on high reward trials.
Figure 3.
Group differences in reward processing in the left VS.
A) Effect of absolute reward magnitude processing. There was a trend for adults compared to adolescents to demonstrate a more linear increase in anticipatory reward activation as a function of absolute reward magnitude at the point of peak activation (6 seconds post-stimulus onset; p = .07). B) Relative reward activity in VS to $1 reward. Based on paired t-tests for each age group, results showed that adults showed greater activity at 6 seconds post-stimulus onset in the $1 amid $.20 alternatives condition (p = .01). The same effect was not significant for adolescents (p = .65).
Figure 4.
Group differences in reward processing in the mesial PFC.
Only hit trials were included for mesial PFC time courses. A) Effect of absolute reward magnitude processing in mesial PFC. There was a main effect at 8 s as a function of absolute reward value (p = .01). However, there were no significant interaction effects between absolute reward value and age group at any time point (ps>.05). B) Relative reward activity to the $1 reward in mesial PFC. A paired t-test indicated that adults did show a difference in the degree to which mesial PFC activity decreased as a function of relative reward value at Time 0 (p = .01). However, none of the interaction effects between relative reward value and age group were significant at any time point (ps>.05).
Table 1.
Correlations between net difference in reward activity in the VS and Impulsivity.
Figure 5.
Anticipated absolute reward magnitude activity in adolescents and adults for the whole brain analyses.
Results are shown on a coronal slices for the VS (y = 8). Although the direct comparison between the two groups was not significant, the within group analyses show that the adults demonstrated strong, bilateral activation in the VS and other adjacent regions whereas the effect was much weaker in the adolescents. P-value threshold set to .005 as in other whole brain analyses.
Table 2.
Regions demonstrating significant activity for absolute anticipation.
Table 3.
Regions demonstrating significant activity for relative anticipation.
Table 4.
Regions demonstrating significant activity to amount of gain vs. failure to gain.