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Background: Tobacco addiction is a chronic, relapsing mental disorder characterized by compulsive tobacco seeking and smoking. Current evidence shows that tobacco addiction exerts their initial reinforcing effects by activating reward circuits in the brain, but the causal connectivity among reward circuits is still unclear. Therefore, it is vital to understand how the reward network works to lead to the compulsive smoking behaviour.Method: We applied dynamic causal modelling (DCM) to resting-state functional magnetic resonance (rs-fMRI) to characterize changes in effective connectivity (EC) among eight major hubs from reward network between 76 long-term male smokers and 55 nonsmoking volunteers (matched with age, gender and education).Results: Relative to the healthy controls, long-term smokers had stronger ECs from the right anterior insula to left ventral striatum, posterior cingulate cortex (PCC) to ventral tegmental area (VTA), PCC to left anterior insula, left anterior insula to VTA, and ventromedial prefrontal cortex (vmPFC) to PCC and weaker ECs from the VTA to left ventral striatum, right anterior insula to right ventral striatum, and anterior cingulate cortex (ACC) to right anterior insula.Conclusions: Overall, our findings revealed disrupted neural causal interactions among parts of the reward network associated with tobacco addiction, expanding the growing evidence for the potential neurobiological mechanisms of tobacco addiction. We found abnormalities within the mesocorticolimbic system and a top-down regulation disorder in the dopamine-dependent process of response inhibition and salience attribution among long-term smokers, which may facilitate the development of effective therapies in tobacco addiction. [ABSTRACT FROM AUTHOR]

Understanding the neural substrates of depression is crucial for diagnosis and treatment. Here, we review recent studies of functional and effective connectivity in depression, in terms of functional integration in the brain. Findings from these studies, including our own, point to the involvement of at least four networks in patients with depression. Elevated connectivity of a ventral limbic affective network appears to be associated with excessive negative mood (dysphoria) in the patients; decreased connectivity of a frontal‐striatal reward network has been suggested to account for loss of interest, motivation, and pleasure (anhedonia); enhanced default mode network connectivity seems to be associated with depressive rumination; and diminished connectivity of a dorsal cognitive control network is thought to underlie cognitive deficits especially ineffective top‐down control of negative thoughts and emotions in depressed patients. Moreover, the restoration of connectivity of these networks—and corresponding symptom improvement—following antidepressant treatment (including medication, psychotherapy, and brain stimulation techniques) serves as evidence for the crucial role of these networks in the pathophysiology of depression. [ABSTRACT FROM AUTHOR]

Background and Objective: Several studies have shown that repetitive transcranial magnetic stimulation (rTMS), applied to the dorsolateral prefrontal cortex (DLPFC), can reduce cue-elicited craving in smokers. Currently, the mechanism of this effect is unknown. We used functional magnetic resonance imaging (fMRI) to explore the effect of a single treatment of rTMS on cortical and sub-cortical neural activity in non-treatment seeking nicotine-dependent participants.Methods: We conducted a randomized, counterbalanced, crossover trial in which participants attended two experimental visits separated by at least 1 week. On the first visit, participants received either active, or sham rTMS (10 Hz, 5 s-on, 10 s-off, 100% motor threshold, 3,000 pulses) over the left DLPFC, and on the second visit they received the opposite condition (active or sham). Cue craving fMRI scans were completed before and after each rTMS session.Results: A total of 11 non-treatment seeking nicotine-dependent cigarette smokers were enrolled in the study [six female, average age 39.7 ± 13.2, average cigarettes per day 17.3 ± 5.9]. Active rTMS decreased activity in the contralateral medial orbitofrontal cortex (mOFC) and ipsilateral nucleus accumbens (NAc) compared to sham rTMS.Conclusions: This preliminary data suggests that one session of rTMS applied to the DLPFC decreases brain activity in the NAc and mOFC in smokers.Scientific Significance: rTMS may exert its anti-craving effect by decreasing activity in the NAc and mOFC in smokers. Despite a small sample size, these findings warrant future rTMS/fMRI studies in addictions. (Am J Addict 2017;26:788-794). [ABSTRACT FROM AUTHOR]