It is also possible that these substance users had a higher visual cortex response to these cues even before they initiated and escalated their use. That is, the occipital cortex activity to drug cues may not reflect an attentional bias that has developed over time, but rather a preexisting sensitivity to drug cues. In a society which both aggrandizes and demonizes images of drugs, it is possible that drug-related images are particularly salient even before being paired with the experience of using the drugs. That said, the few studies in this meta-analysis that showed images of drug cues (typically alcohol or smoking) to non-drug users however did not report significant activity in the occipital cortex among the non-drug users. Future longitudinal investigations of adolescents at risk for substance dependence (e.g., those with a positive family history of alcohol dependence or high sensation-seekers) may be able to test directly whether visual cortex activity to drug related images, and visual fixation, predicts drug initiation even before a traditional Stroop-related attentional bias develops. Although fMRI will likely never be a realistic screening tool
