Facial EMG as an index of affective response to nicotine

Watching happy faces potentiates incentive salience but not hedonic reactions to palatable food cues in overweight/obese adults

'Wanting' and 'liking' are mediated by distinct brain reward systems but their dissociation in human appetite and overeating remains debated. Further, the influence of socioemotional cues on food reward is little explored. We examined these issues in overweight/obese (OW/OB) and normal-weight (NW) participants who watched food images varying in palatability in the same time as videoclips of avatars looking at the food images while displaying facial expressions (happy, disgust or neutral) with their gaze directed only toward the food or consecutively toward the food and participants. We measured heart rate (HR) deceleration as an index of attentional/incentive salience, facial EMG activity as an index of hedonic or disgust reactions, and self-report of wanting and liking. OW/OB participants exhibited a larger HR deceleration to palatable food pictures than NW participants suggesting that they attributed greater incentive salience to food cues. However, in contrast to NW participants, they did not display increased hedonic facial reactions to the liked food cues. Subjective ratings of wanting and liking did not differentiate the two groups. Further, OW/OB participants had more pronounced HR deceleration than NW participants to palatable food cues when they watched avatars' happy faces gazing at the food. In line with the "incentive-sensitization" hypothesis, our data suggest that incentive salience attribution and not hedonic reactivity is increased in OW/OB individuals and that happy faces, as social reward cues, potentiate implicit wanting in OW/OB people.

Association of the OPRM1 Variant rs1799971 (A118G) with Non-Specific Liability to Substance Dependence in a Collaborative de novo Meta-Analysis of European-Ancestry Cohorts

The mu1 opioid receptor gene, OPRM1, has long been a high-priority candidate for human genetic studies of addiction. Because of its potential functional significance, the non-synonymous variant rs1799971 (A118G, Asn40Asp) in OPRM1 has been extensively studied, yet its role in addiction has remained unclear, with conflicting association findings. To resolve the question of what effect, if any, rs1799971 has on substance dependence risk, we conducted collaborative meta-analyses of 25 datasets with over 28,000 European-ancestry subjects. We investigated non-specific risk for "general" substance dependence, comparing cases dependent on any substance to controls who were non-dependent on all assessed substances. We also examined five specific substance dependence diagnoses: DSM-IV alcohol, opioid, cannabis, and cocaine dependence, and nicotine dependence defined by the proxy of heavy/light smoking (cigarettes-per-day >20 vs. ≤ 10). The G allele showed a modest protective effect on general substance dependence (OR = 0.90, 95% C.I. [0.83-0.97], p value = 0.0095, N = 16,908). We observed similar effects for each individual substance, although these were not statistically significant, likely because of reduced sample sizes. We conclude that rs1799971 contributes to mechanisms of addiction liability that are shared across different addictive substances. This project highlights the benefits of examining addictive behaviors collectively and the power of collaborative data sharing and meta-analyses.

Effects of amphetamine on reactivity to emotional stimuli

RATIONALE

Most studies of the reinforcing effects of stimulants have focused on the drugs' capacity to induce positive mood (i.e., euphoria). However, recent findings suggest drugs may also alter emotional reactivity to external stimuli, and that this may occur independently of direct effects on mood.

OBJECTIVES

We aimed to examine effects of D: -amphetamine, a prototypic stimulant, on self-reported and psychophysiological reactivity to emotional stimuli as well as overall subjective mood. We predicted that amphetamine would enhance reactivity to pleasant stimuli, particularly, stimuli with social content and that these effects would be independent of the drug's direct effects on mood.

METHODS

Over three sessions, 36 healthy normal adults received placebo, D: -amphetamine 10 and 20 mg under counterbalanced double-blind conditions. At each session, emotional reactivity to standardized positive, neutral, and negative pictures with and without social content was measured in self-reports and facial muscles sensitive to emotional state. Drug effects on cardiovascular variables and subjective mood were also measured.

RESULTS

Amphetamine produced euphoria, feelings of drug effect, and increased blood pressure. Most notably, amphetamine enhanced self-reported positive reactions to all pictures and psychophysiological reactions to positive pictures. These effects were not significantly related to drug-induced mood changes. Contrary to our hypothesis, effects of amphetamine on emotional reactivity were not moderated by social content.

CONCLUSIONS

This study demonstrates a previously unexamined and potentially reinforcing effect of stimulant drugs in humans, distinct from more typically measured euphorigenic effects, and suggests new areas of research in stimulant abuse risk and adaptations occurring during drug dependence.

Negative reinforcement smoking outcome expectancies are associated with affective response to acute nicotine administration and abstinence

BACKGROUND

Negative affect is an important predictor of smoking behavior, and many smokers believe that smoking reduces negative affect. However, it is unclear whether such beliefs, known as negative reinforcement smoking outcome expectancies (NRSOE), are associated with changes in negative affect in response to nicotine deprivation and administration.

METHODS

Smokers (N=114) participated in 4 sessions that balanced overnight smoking deprivation (12-h deprived vs. ad lib) and nasal spray administration (nicotine vs. placebo). Corrugator supercilii (COR) EMG, skin conductance (SCR), and in-session ratings were collected while the participants viewed affective, cigarette-related, and neutral slides. Retrospective questionnaire data were collected prior to slide viewing. NRSOE were determined using the Smoking Consequences Questionnaire - Adult Nicotine Affect Reduction scale (SCQ-NAR).

RESULTS

High scores on the SCQ-NAR were associated with smaller COR EMG to unpleasant slides following nicotine nasal spray administration compared to placebo spray, regardless of overnight deprivation. Smokers who had high scores on the SCQ-NAR had smaller SCR, following nicotine nasal spray administration compared to placebo spray, but only after overnight deprivation. The in-session ratings and retrospective questionnaire measures indicated that smokers who had high scores on the SCQ-NAR experienced greater negative affect and craving, and less positive affect, than smokers with low scores on the SCQ-NAR, regardless of nicotine exposure.

CONCLUSIONS

Our questionnaire results suggest that while smokers who have high NRSOE self-report greater overall levels of negative affect and craving, while the psychophysiological data suggest that such smokers may experience negative affect reduction when blindly administered a dose of nicotine.

Emotional reactivity to emotional and smoking cues during smoking abstinence: potentiated startle and P300 suppression

Negative affect is thought to be an important factor in the maintenance of cigarette smoking, and thus it is important to further develop objective measures of smoking-related emotional responses. Nonsmokers, non abstinent smokers, and abstinent smokers participated in a cue reactivity task where eyeblink startle amplitude and startle probe P300 (P3) suppression were measured during the presentation of emotional pictures.During unpleasant pictures, the amplitude of both measures was smaller in non abstinent smokers than in nonsmokers or abstinent smokers. P3 suppression, but not startle amplitude, was larger in abstinent smokers than in nonsmokers. Abstinence-induced increases in cigarette craving were associated with P3 suppression during tobacco-related pictures. Results suggest that tobacco abstinence increases emotional reactivity to unpleasant stimuli, which is consistent with negative reinforcement models of tobacco addiction.

A multimodal approach to assessing the impact of nicotine dependence, nicotine abstinence, and craving on negative affect in smokers

We used multimodal measurement to evaluate whether (a) nicotine dependence is associated with baseline and postquit negative affect and craving, (b) smoking relapse is associated with greater negative affect and craving than abstinence, and (c) craving is associated with negative affect. Treatment-seeking smokers were randomly assigned to either a brief behaviorally based smoking-cessation treatment condition or to a delayed treatment control condition. Participants in the treatment condition attended four assessment sessions, 4-5 days prequit (baseline), 1-2 days postquit, 3-5 days postquit, and 10-14 days postquit, while controls attended four sessions spaced over the same intervals. Retrospective questionnaires were collected at the beginning of each session, and corrugator EMG and in-session ratings were collected during viewing of affective and cigarette-related slides. The multimodal measures indicated that more dependent smokers experienced greater negative affect and craving at baseline and postquit, regardless of abstinence status. The self-report measures indicated that both relapsed and abstinent smokers reported greater negative affect and craving than control smokers. Craving was associated with negative affect across measurement modalities. These results highlight the benefits of using multimodal measures to study the impact of nicotine dependence and withdrawal on negative affect and craving.

Attentional bias is associated with incentive-related physiological and subjective measures

Drug cue reactivity is theoretically and clinically important. The modified Stroop task has been widely used to assess attention capture by drug cues (attentional bias). Attentional bias to drug cues is assumed to reflect the incentive value of those cues, but this has not been directly tested. The authors examined whether the smoking Stroop effect was associated with facial electromyography (EMG) assessed in real time. Heart-rate (HR) and skin conductance (SC) responses were also assessed. Smokers (n = 79) attended up to four experimental sessions. Presession Abstinence state and within-session Smoking were manipulated across sessions. Over all assessments, participants exhibited a robust smoking Stroop effect. Using Generalized Estimating Equations (GEE) analyses, the smoking Stroop effect was positively associated with zygomaticus major activity but not with corrugator supercilii activity, HR, or SC. The smoking Stroop effect was also positively associated with self-reported positive outcome expectancies from smoking and with craving. In sum, attentional bias was more strongly associated with appetitive responses (zygomaticus major activity, positive outcome expectancies) than with withdrawal responses (e.g., corrugator supercilii activity) or measures of physiological arousal (e.g., HR, SC).