Correlation analyses.

<p>A) Correlation between delay discounting (% delayed choices short – long delays) (x-axis) and % BOLD signal change for immediate choice options in the ventral striatum (y-axis). Younger adults are shown in black, older adults are shown in grey. B) Correlation between delay discounting (x-axis) and reaction time for choice options involving delayed reward (y-axis). Younger adults are shown in black, older adults are shown in grey.</p

Regions of interest (ROI) analysis of BOLD activity in the nucleus accumbens.

<p>A) Time courses for immediate (dashed) and delayed (solid) choice options in the nucleus accumbens (Nacc, as defined using Talairach atlas). Younger adults (top) are shown in black, older adults (bottom) are shown in grey. B) For younger adults (top) BOLD signal change for immediate choice options in the nucleus accumbens correlates positively with discounting. In contrast, BOLD signal change for delayed choice options correlates negatively with discounting. For older adults (bottom) no significant correlations are obtained.</p

Age differences in striatal activity.

<p>A) Left: Significant main effect of age group for choice options involving immediate reward in the ventromedial caudate (t-statistics, significant at p<.05, corrected for multiple comparisons). Right: Time course of BOLD signal change (on the y-axis) for younger (black) and older adults (grey). The x-axis shows time post stimulus onset in seconds. The coordinates refer to Talairach space. B) Left: Significant main effect of age group in the dorsal striatum for all choice options (t-statistics, significant at p<.05, corrected for multiple comparisons). Right: Time course of BOLD signal change (on the y-axis) for younger (black) and older adults (grey). The x-axis shows the repetition time (TR) in seconds. The x-axis shows time post stimulus onset in seconds. The coordinates refer to Talairach space.</p

Activity in β-areas and δ- areas across age groups.

<p>Left: Significant activations (t-statistics) for choice pairs involving immediate options (β-areas) averaged across age groups. Talairach coordinates: MFG: -8, 57, 19; vmPFC: 0, 39, -4; PCC: 2, −52, 31. Right: Significant activations for all choice pairs (δ- areas). Activations are significant at p<.05, corrected for multiple comparisons. Talairach coordinates: dlPFC: −42, 36, 22; IFG: −45, 7, 32; Ins: −35, 22, 3; SMA; −1, 15, 48; IPL: 30, −48, 40.</p

The trial components’ timing.

<p>Each trial lasted 18 s. The <i>n</i>-back stimulus was presented at 250 ms and subjects were asked to respond immediately. At 6, 8, or 10 s following stimulus onset, subjects received 0.5 ml boluses of either juice or quinine solution in their mouths. On the half the trials (50 percent probability represented by grey line), a flickering checkerboard was shown for 500 ms at 6, 8 or 10 s following stimulus onset, but never when juice or quinine was delivered. The timing of the solution administration and checkerboard were determined by a permutation table (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130880#pone.0130880.s007" target="_blank">S1 Table</a>), each of the six outcomes of which are displayed here.</p

Reward processing regions had a load-related reduction of BOLD response to juice and quinine, but visual stimulation was not modulated.

<p>Regions A-C show where there was significant load-related BOLD reduction, and corresponded to the regions listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130880#pone.0130880.t001" target="_blank">Table 1</a>. Region A is in the left striatum. Region B is in the right striatum. Region C is the dorsal anterior cingulate region. Neurological convention.</p

Regions showing load-related reduction of BOLD responses to hedonic stimuli (juice and quinine combined).

<p>* Center of mass</p><p>^† 95% confidence interval Bonferroni-corrected for number of ROIs</p><p>Regions showing load-related reduction of BOLD responses to hedonic stimuli (juice and quinine combined).</p

Load did not affect the checkerboard BOLD response.

<p>This shows BOLD responses to the flickering checkerboard stimulus within a predefined AFNI anatomical mask for BA 17. This region exhibited no significant <i>n</i>-back modulation. Estimated hemodynamic responses are statistically independently of the ROI selection (a predefined anatomical mask). Error bars show s.e.m.</p