Another common limitation found in some FC studies is the lack of a clear separation between alcohol and nicotine consumption. Although it is known that the effects of alcohol and nicotine are moderately to strongly related (Istvan and Matarazzo, 1984), combined and separate influences of nicotine and alcohol use in resting state FC have not been thoroughly studied. In this work, we have carefully selected subjects that smoke nicotine and drink alcohol in a separate or combined manner. We hypothesize that different patterns of FC exist depending on drinking, smoking or combined drinking and smoking. Based on previous research we expect to see decreased connectivity associated with reward, executive control, default mode and visual brain areas in alcohol users (Camchong et al., 2012; Chanraud et al., 2011; Weiland et al., 2014). With respect to nicotine use, both increases and decreases in connectivity effects are anticipated for cingulated cortex, precuneus, and executive function areas (Pariyadath et al., 2014). Common neural pathways for drug dependence exist, but alcohol and nicotine have different mechanisms of action. While nicotine seems to be able to
