Genes of interest (that is, meeting a P-value threshold of less than 1 × 10−4) were compared with microarray data from nine brain regions (prefrontal cortex, cerebral cortex, thalamus, visual cortex, hippocampus, amygdala, caudate nucleus, putamen and cerebellum) from post-mortem tissue from two males and two females, which included an alcoholic and a control of each sex, to determine whether they were expressed in the brain.32 These nine regions were chosen to provide broad coverage across the brain. The expression values for our genes of interest did not substantially vary across these regions, and we therefore report the maximum of the average expression value. A gene was presumed to be expressed in the brain if the maximum expression level across the nine regions was higher than 16.0, because this is above the background signal for the arrays.
