ABSTRACT
INTRODUCTION: The neural underpinnings underlying individual differences in nicotine-enhanced reward sensitivity and smoking progression are poorly understood. Thus, we investigated whether brain resting-state functional connectivity (rsFC) during smoking abstinence predicts nicotine-enhanced reward sensitivity and smoking progression in young light smokers. We hypothesized that high rsFC between brain areas with high densities of nicotinic receptors (insula, anterior cingulate cortex [ACC], hippocampus, thalamus) and areas involved in reward-seeking (nucleus accumbens [NAcc], prefrontal cortex [PFC]) would predict nicotine-enhanced reward sensitivity and smoking progression. METHODS: Young light smokers (N=64, age 18-24, M = 1.89 cigarettes/day) participated in the study. These individuals smoked between 5 to 35 cigarettes per week and lifetime use never exceeded 35 cigarettes per week. Their rsFC was assessed using functional magnetic resonance imaging after 14-hour nicotine-deprivation. Subjects also completed a probabilistic reward task after smoking a placebo on one day and a regular cigarette on another day. RESULTS: The probabilistic-reward-task assessed greater nicotine-enhanced reward sensitivity was associated with greater rsFC between the right anterior PFC and right NAcc, but with reduced rsFC between the ACC and left inferior prefrontal gyrus and the insula and ACC. Decreased rsFC within the salience network (ACC and insula) predicted increased smoking progression across 18 months and greater nicotine-enhanced reward sensitivity. CONCLUSIONS: These findings provide the first evidence that differences in rsFCs in young light smokers are associated with nicotine-enhanced reward sensitivity and smoking progression. IMPLICATIONS: Weaker rsFC within the salience network predicted greater nicotine-enhanced reward sensitivity and smoking progression. These findings suggest that salience network rsFC and drug-enhanced reward sensitivity may be useful tools and potential endophenotypes for reward sensitivity and drug-dependence research.
ABSTRACT
OBJECTIVE: To assess: (1) the acute effects of smoked marijuana (MJ) on negative attentional bias (NAB), (2) moderation of these effects by positive versus neutral alternatives, and (3) the associations of tetrahydrocannabinol (THC)-induced changes in NAB with changes in affect. METHODS: Fourteen MJ users (1-4 uses/wk) smoked a THC cigarette on 1 day and a placebo cigarette on the other counterbalanced day. After smoking, participants freely gazed back and forth at a series of two side-by-side pictures pairs presented for 3000 ms (one negative, while the other was either positive or neutral) while eye gaze was tracked. RESULTS: The effects of THC relative to placebo varied across time such that THC increased NAB during the early temporal component of threatening picture viewing, 333-858 ms after dual-picture onset, regardless of alternative picture valance. However, contrary to the attentional bias-causes affect hypothesis, during the early viewing phase THC-enhanced positive affect (PA) correlated positively with THC-induced NAB. In contrast, during the late phase (891-3000 ms) THC-enhanced PA did not correlate significantly with NAB, though THC-induced negative affect (NA) change did correlate positively with THC-induced change in NAB in the positive alternative condition. CONCLUSIONS: We replicated findings of others showing that THC can enhance NAB during the early stages of threatening picture viewing. We extended previous results by demonstrating the THC-induced NAB is associated with increased PA during initial threat viewing, but with increased NA during later processing if positive alternatives are present.
