Table 2.
Group and individual differences in drug modulations of SM-related activity
| Location (x, y, z) | Peak Z (n) | Region | Brodmann area | Follow-up contrasts significant for group differences | Follow-up contrasts significant in young group | Follow-up contrasts significant in old group |
| −30, −39, −9 | 4.39 (26) | Left posterior parahippocampal gyrus/hippocampus | BA 37/19/— | O > Y lin | — | Overall, Pos lin |
| 33, 6, 27 | 4.31 (31) | Right precentral/inferior frontal gyrus | BA 6/44 | O > Y lin, B vs. P | (Neg lin at 0.005) | Overall, B vs. P |
| 12, 9, 15 | 4.21 (33) | Right caudate body | — | O > Y lin, B vs. P | (Neg lin at 0.005) | Overall, Pos lin, B vs. P |
| −15, 15, 9 | 4.11 (71) | Left caudate body | — | O > Y lin, B vs. P | — | Overall, Pos lin, B vs. P |
| 15, 21, −3 | 3.75 (17) | Right caudate head | — | O > Y lin | (Neg lin at 0.005) | Overall, Pos lin |
| −33, 24, −6 | 3.70 (13) | Left inferior frontal gyrus (anterior) | BA 47 | O > Y lin, B vs. P | — | Overall, Pos lin |
| −42, 3, 27 | 3.60 (19) | Left inferior frontal gyrus | BA 9 | O > Y lin, B vs. P | — | B vs. P |
| −33, 42, 12 | 3.29 (5) | Right anterior middle frontal gyrus | BA 10 | B vs. P | (B vs. P at 0.01) | (B vs. P at 0.01) |
Note: Regions showing an interaction of age group × drug × Pr are shown (contiguous clusters of ≥5 voxels at P < 0.001, uncorrected, see Methods). N refers to the number of significant voxels in each cluster; Z refers the Z statistic value for each peak or subpeak; and x, y, and z refer to distances in millimeter from the origin in MNI space (see Materials and Methods). The results of follow-up contrasts are also shown. These tested interactions of drug × Pr in the 2 groups together for each drug versus Placebo separately, that is, Sulpiride versus Placebo, and Bromocriptine versus Placebo (S vs. P and B vs. P). Further tests assessed positive and negative linear forms of this contrast in the groups separately, and group differences in these effects: Pos lin and Neg lin indicate weightings of the Pr covariate with [−1 0 1] and [1 0 −1] respectively across the Sulpiride, Placebo, and Bromocriptine conditions, and O > Y indicates a linear effect that is more positive in the old than in the young (see text in Results section and Materials and Methods). For the follow-up tests, findings from comparisons using more lenient thresholds are shown in brackets to indicate trends.