Self-report of drug use
Self report data are given in . The MA group had used the drug, on average, for > 8 years; consumed about 2-4 g/week, and had used MA on most of the 30 days before entering the study.
Self-report of depressive symptoms
Control subjects reported low ratings of depressive symptoms at the initial measurement (eight BDI scores of 0, two scores of 1, and two scores of 3). Participants in the MA group gave higher self-ratings than control subjects at 5-9 days of abstinence (mean [SD] 5.8 [6.4], (t = 2.73, p = .01). Four weeks later, one control subject reported a 1-unit increase in BDI score. No other scores changed. In contrast, half of the MA group showed a BDI change ≥ 4 units at retest (2 increases, 3 decreases). Although the MA group as a whole reported a 29.3% reduction in BDI score after 4 weeks (from 5.8 to 4.1 [6.1]), this reduction was not significant (t = 0.93, p = .38). At retest, there was no longer a significant difference between groups (t = 1.88, p = .08).
Vigilance task performance
Accuracy on the vigilance task decreased in both groups at retest (MA initial mean [SD] 96.0% [4.4], retest 94.1% [5.6]; control 98.1% [2.3], retest 96.1% [3.3]). Although the Session-by-Group interaction was not significant (F 1, 20 = .01, p = .93), the decrease attained significance in the control group (p = .02) but not in the MA group (p = .37). Since the mean decrease was similar (MA 1.9%; control 2.0%), this finding appeared to be due to larger variance of the change score in the MA group (SD = 6.0%) vs control group (2.5%); Levene’s Test for equality of variance (F = 3.85, p = .06).
Mean RT was 4 ms shorter at retest in the control group (Mean [SD] 664 ms  vs. 660 ms ) and 43 ms longer in the MA group (714 ms  vs. 757 ms ). These effects and the Session-by-Group interaction (F 1, 20 = 0.40, p = .53) were not significant. However, there was significantly greater variance in the RT change score for the MA group (43 ms ) than in the control group (4 ms ), as indicated by Levene’s Test for equality of variance (F = 5.68, p = .03).
The total sample showed a significant increase in global CMRglc from the first to the second measurement (F 1, 14 = 8.67, p = .01). The Session-by-Group interaction bordered on significance (F 1, 14 = 4.31, p = .06). Planned comparisons indicated that in the MA group, a 10.9% increase in CMRglc was significant (9.84 vs. 10.91, t 8 = 2.94, p = .02), whereas in the control group the 1.9% increase was not significant (10.19 vs. 10.38, t 6 = 1.71, p = .14).
Analyses of the interaction of group with session indicated larger increases at retest in the MA group or decreases in the control group based on volume-corrected spatial-extent p-values in both right and left parietal lobe ROIs (). These effects maintained statistical significance after Bonferroni correction. Peak voxel effects were significant in the parietal lobes, the lateral orbitofrontal cortex, supragenual cingulate cortex, insula, and thalamus, although voxel effects did not maintain statistical significance after Bonferroni correction. depicts this interaction over much of the cerebral grey matter, including prominent effects in parietal cortex.
Interaction of Group with Change in Absolute rCMRglc
Parietal cortex CMRglc increased between sessions in the MA abuse group, more than in the control group
Separate analysis of the change across session within each group confirmed that the effects depicted in were due solely to widespread increases in the MA group. They attained Bonferroni-corrected spatial-extent significance in bilateral parietal lobe, lateral orbitofrontal cortex, insula and supragenual cingulate gyrus (). Peak voxel effects attained Bonferroni-corrected significance in bilateral parietal lobe, right lateral orbitofrontal cortex and right insula. Whole brain statistical analysis revealed that no voxel in the MA group showed a decrease in CMRglc of p < .01, even prior to correction for multiple comparisons.
Regional relative radioactivity
The interaction of group with session produced evidence for greater increase in the MA group or decrease in the control group by the criterion of spatial-extent in the right parietal lobe (p = .033), and of peak height in the parietal lobes (left p = .029; right p = .023), right lateral orbitofrontal cortex (p = .017), and right insula (p = .028). A peak voxel in the left dorsal striatum had a greater decrease in the MA group, or increase in the Control group, (p = .017). No effects survived Bonferroni correction.
However, separate analysis of the MA group confirmed an increase in the bilateral parietal lobes (left and right spatial-extent p <.0005; both peak voxel z > 4.8, both p = .001), and right lateral orbitofrontal cortex (spatial-extent p <.003; peak voxel z = 4.21, p = .003). All parietal effects retained significance after Bonferroni correction, but the orbitofrontal cortex effects did not.
Relationship between changes in regional CMRglc or relative radioactivity and vigilance task performance
In the control group, there was no relationship between RT change and either regional CMRglc or relative radioactivity.
In the MA group, the amount of RT slowing was associated with increases in regional CMRglc by the criterion of spatial extent for clusters in the left (32 voxels, p = .047) and right parietal lobes (166 voxels, p = .004). The peak voxel effect in the right parietal lobe (14, −62, 48) was also significant (Z = 4.38, p = .024). Although the amount of RT slowing was not associated with increased relative radioactivity in any ROI, it was associated with a decrease in 7 of the 20 ROIs by the criterion of peak voxel-height (). Six of these ROIs were also significant for spatial extent, with the largest effects in ventromedial orbitofrontal cortex (). The spatial-extent effect in the right medial orbitofrontal cortex retained significance after Bonferroni correction.
MA Group: Association of Change in RT to Change in Relative Brain Activity
Between-session directional change in relative radioactivity of medial orbitofrontal cortex was inversely correlated with vigilance reaction time (RT) in the MA abuse group
Relationship between changes in regional CMRglc or relative radioactivity and depressive symptoms in MA Group
As BDI scores were negligible, with no meaningful change between assessments in the control group, these analyses were only conducted for the MA group. The extent of the increase in regional CMRglc in the left parietal lobe was directly associated with BDI score by the criteria of spatial extent (p = .045) and peak voxel height (x,y,z = −32, −40, 64; Z = 4.57, p = .005).
BDI score was correlated with change in relative radioactivity in at least one cerebral hemisphere for all ROIs with the exception of the thalamus (). BDI score was positively correlated with the change in relative radioactivity by criteria for both spatial extent and peak voxel effect in the right parietal lobe, right amygdala, and bilateral ventral striatum, and in the bilateral dorsal striatum by the criterion of peak voxel effect. The peak effect in the right ventral striatum retained significance after Bonferroni correction ().
Association of Change in BDI to Change in Relative Brain Activity
Between-session directional change in relative radioactivity of ventral striatum was directly correlated with self-reported depressive symptoms in the MA abuse group
BDI score was negatively correlated with the change in relative radioactivity (one measure increased when the other decreased) by criteria for both spatial extent and peak voxel effect in the right infragenual cingulate cortex, right supragenual cingulate cortex and right insula. The indirect associations were significant by the peak voxel criterion only in the left insula, right lateral orbitofrontal cortex, and bilateral dorsal striatum, and by the spatial extent criterion only in the right medial orbitofrontal cortex ().