A validated survey measure of the Level of PD allows a smoker’s progress along this continuous developmental sequence to be determined in >99% of cases. (DiFranza et al. 2011) The fact that the three forms of WIC develop in the same sequence in all smokers suggests

that the neural changes responsible for the latent state of PD might also develop in the same sequence in all smokers. This suggests that homeostatic neural Inhibitors,research,lifescience,medical adaptations that underlie PD might be identified by correlating the Level of PD with alterations in neural structure. Indeed, analyses of the diffusion tensor imaging (DTI) data from part of this study (reported elsewhere) identified an inverse correlation (r = −0.68) between the Level of PD and fractional anisotropy (FA, a measure of white matter organization) in the left anterior cingulum bundle

(ACb). (Huang et al. 2013) FA in this area also correlated with scores on the Hooked on Nicotine Checklist (HONC), another measure of nicotine addiction. DTI indicated that progression along the Levels of PD corresponds Inhibitors,research,lifescience,medical with increased density of white matter tracts between the ACb and the precuneus Inhibitors,research,lifescience,medical (r = 0.75, P < 0.05), but decreased density of white matter tracts between the ACb and the white matter approaching the frontal cortex (r = −0.86, P < 0.001). (Huang et al. 2013) As these analyses suggested a role for the ACb in the development of PD, and whereas WIC is the dynamic manifestation of PD, we sought to examine the role of the anterior cingulate cortex (ACC) in WIC. The intensity of WIC experienced Inhibitors,research,lifescience,medical by an individual at any given moment can range from none, up to the maximum intensity associated with their Level of PD. As WIC is a dynamic state, it is suitable for study with resting-state functional connectivity (rsFC). (Biswal et al. 1995; Fox and Raichle 2007) In this experiment, we manipulated the intensity of WIC in order to study the effect on rsFC using the ACC as a seed for rsFC analysis. The sensitization–homeostasis theory attributes the addictive potential of nicotine

to SKI 606 inhibitory properties. Inhibitors,research,lifescience,medical (DiFranza and Wellman 2005; DiFranza et al. 2012a) According to the theory, neuroplastic changes develop to compensate for this inhibition, and during withdrawal, these homeostatic adaptations Rolziracetam autonomously stimulate neural networks that generate WIC. The theory predicts that (1) there is a neural system involved in craving and that activity in this system correlates positively with the intensity of WIC; (2) activity in this system will be greater when smokers are in withdrawal than when they are satiated; and (3) since homeostatic changes stimulate this system during withdrawal, system activity in smokers during withdrawal will be greater than that of nonsmoking controls. By including nonsmoking controls, we were able to test and confirm these theory-driven predictions.