Figure 4: Cortical differences in grey matter volume for control subjects (n=72) versus prospective problematic drug users (PDU) (n=72).

(a) Increased grey matter density was observed for the PDU group in the right dorsolateral prefrontal cortex. (b) The location of increased grey matter density (green) lies adjacent to reduced activation in the Monetary Incentive Delay (MID) task for the prospective problematic drug users (red). Overlaid on a mean structural magnetic resonance scale, volumetric display threshold is P<0.005 (uncorrected, t-test). Highlighted areas indicate volumes of interest in the prefrontal cortex. Error bars=±s.e.m. *Significant at threshold of P<0.0083 uncorrected or P<0.05 corrected (n=144, t-test).