An acute psychosocial stress enhances the neural response to smoking cues.

Stress plays an important role in drug addiction. It can trigger relapse in abstinent addicts, and both in the everyday world and in the laboratory, a stressor can induce drug craving. Drug cues, such as the sight of drug, can also trigger subjective craving and relapse, and this effect may be amplified by stress. Underpinning this interaction may be the fact that stress and reward-predicting drug cues act on overlapping brain regions. We exposed 15 smokers undergoing functional magnetic resonance imaging to a psychosocial stressor, the Montreal Imaging Stress Task, followed by drug cues consisting of video clips of smokers. In a separate session similar video clips were shown after a non-stress control task. We observed significantly decreased neural activity during stress in the hippocampus, amygdala, bed nucleus of the stria terminalis, hypothalamus and nucleus accumbens. Following stress there was an increased neural response to drug cues in the medial prefrontal cortex, posterior cingulate cortex, dorsomedial thalamus, medial temporal lobe, caudate nucleus, and primary and association visual areas. These regions are thought to be involved in visual attention and in assigning incentive value to cues. Stress-induced limbic deactivation predicted subsequent neural cue-reactivity. We suggest that stress increases the incentive salience of drug cues.

Effects of expectancy and abstinence on the neural response to smoking cues in cigarette smokers: an fMRI study.

Cues associated with drug taking can trigger relapse, drug seeking, and craving in addicted individuals. Behavioral studies suggest that drug availability and withdrawal can affect the individual response to drug cues. Moreover, the importance of subjective craving in cue-induced relapse has been questioned and an alternative model put forward according to which drug cues trigger habitual drug-seeking behaviors independently of craving. We used functional magnetic resonance imaging to compare the brain response to smoking and control videotapes in 20 healthy smokers, while varying their expectancy to smoke and abstinence levels. The neural response to cigarette cues was strongly modulated by expectancy and, to a lesser extent, abstinence. In people expecting to smoke immediately after the scan, smoking cues activated brain areas implicated in arousal, attention, and cognitive control. However, when subjects knew they would not be allowed to smoke for 4 h, there was almost no brain activation in response to smoking cues, despite equivalent reported levels of craving. In the dorsolateral prefrontal cortex, the neural response was a function of both craving and expectancy. Thalamo-cingulate connectivity, thought to be an index of arousal, was greater during expectancy than nonexpectancy. Our findings confirm the importance of expectancy in the neural response to drug cues, and lend support to the theory that these cues act on brain areas involved in arousal and attention.