As discussed, visual cortex activity is modulated by both attention and reward. From the perspective of addiction, it is well established that substance dependent individuals have elevated attentional bias to drug-related cues (reviews see: Field and Cox, 2008; Robbins and Ehrman, 2004). One theory of attentional bias in addiction is that over time, as the individual repetitively uses the substance and finds it rewarding, incentive salience for the substance transfers to the substance-related cue. The cue then elicits a conditioned motivational state (Robinson and Berridge, 1993) which promotes attentional bias towards the drug cue (Goldstein and Volkow, 2002; Robinson and Berridge, 1993), and subsequent craving (Waters et al., 2012). The attentional bias to cues is remarkably frequent and stable across drug classes. This has led to enthusiasm about attentional bias being a potential biomarker for addiction, an indicator of vulnerability, or even a treatment target.
