Figure 7.

Prefrontal cortex correlations with heroin use severity measures in iHUDs. A, B, Fewer days since last use was associated with lower SMA activity (A), and higher severity of dependence was associated with lower aPFC activity (B) during successful compared with failed stops (the hallmark inhibitory control contrast) in iHUDs. Significant results were detected within a small volume corrected PFC mask, using a cluster-defining threshold of Z > 3.1, corrected for familywise error for five heroin use severity measures (p < 0.05/5 = 0.01). In A two participants' days since last use were 3 SDs above the mean. Excluding these outlier data points did not substantially affect the results (R² = 0.34, p < 0.001). One participant's SMA activity was identified as an outlier, and excluding this data point reduced this correlation to a trend level when accounting for five heroin use severity measures (R² = 0.16, p = 0.012, α = 0.01). Nevertheless, a robust regression including the outliers supported the significant effect when assuming a normal t distribution (t = 4.908, β = 1.147, SE = 0.23, p < 0.001). The SMA outlier data point is denoted in gray, with the regression line reflecting all data points. Coordinates are in the MNI-152 space.