Attention can increase the gain, reduce the noise, and reduce noise correlations in response to attended visual stimuli (Pratte et al., 2013; Keitel et al., 2013). Any of these attention-related effects could result in the increased probability of activation to drug cues noted in our meta-analysis. Thus, one way in which addiction might exert it effects upon sensory processing in BA 17 is by establishing an attentional bias toward images, either external or internally generated, that depict drug-related materials. Such an attentional bias could increase the likelihood of relapse by increasing drug craving (Field and Cox, 2008). Thus, an important future direction of this work will be to determine if an attentional bias toward drug-related cues can explain our finding of increased visual cortex activity in response to drug cues. This could be done, for example, by determining if BA 17 in non-users shows enhanced activation when subjects are specifically instructed to attend to drug-related cues. If so, it will then be important to assess whether or not this attentional bias is effectively permanent, or if it can be manipulated or diverted by, for example, a demanding attentional task.
