Effects of nicotine and depressive traits on affective priming of lateralized emotional word identification

Depressive symptoms and responses to cigarette pack warning labels among Mexican smokers

OBJECTIVE

We examine whether having depressive symptoms (DS) is associated with different responses to cigarette package health warning labels (HWLs) before and after the implementation of pictorial HWLs in Mexico.

METHOD

We analyze data from adult smokers from Wave 4 and Wave 5 (n = 1,340) of the International Tobacco Control Policy Evaluation Project in Mexico. Seven Center for Epidemiological Studies Depression Scale (CES-D) items assessed DS, with scores ≥7 indicating elevated DS. Outcomes included: attention to HWLs, cognitive responses to HWLs, tobacco constituents awareness, putting off smoking due to HWLs, avoidance of HWLs, and awareness of telephone support for cessation (i.e., quitlines). Mixed effects models were used to assess main and interactive effects of DS and time (i.e., survey wave) on each outcome.

RESULTS

All HWL responses increased over time, except putting off smoking. Statistically significant interactions were found between DS and time for models of tobacco constituents awareness (b = -0.36, SE = 0.15, p = .022), putting off smoking (OR = 0.41, 95% CI [0.25, 0.66]), avoidance of HWLs (OR = 1.84, 95% CI [1.03, 3.29]), and quitline awareness (OR = 0.35, 95% CI [0.21, 0.56]). Compared to smokers with low DS, smokers with elevated DS reported stronger HWL responses at baseline; however, HWL responses increased over time among smokers with low DS, whereas HWL responses showed little or no change among smokers with elevated DS.

DISCUSSION

Population-level increases in HWL responses after pictorial HWLs were introduced in Mexico appeared mostly limited to smokers with low DS. In general, however, smokers with elevated DS reported equivalent or stronger HWL responses than smokers with low DS.

Left medial orbitofrontal cortex volume correlates with skydive-elicited euphoric experience

The medial orbitofrontal cortex has been linked to the experience of positive affect. Greater medial orbitofrontal cortex volume is associated with greater expression of positive affect and reduced medial orbital frontal cortex volume is associated with blunted positive affect. However, little is known about the experience of euphoria, or extreme joy, and how this state may relate to variability in medial orbitofrontal cortex structure. To test the hypothesis that variability in euphoric experience correlates with the volume of the medial orbitofrontal cortex, we measured individuals' (N = 31) level of self-reported euphoria in response to a highly anticipated first time skydive and measured orbitofrontal cortical volumes with structural magnetic resonance imaging. Skydiving elicited a large increase in self-reported euphoria. Participants' euphoric experience was predicted by the volume of their left medial orbitofrontal cortex such that, the greater the volume, the greater the euphoria. Further analyses indicated that the left medial orbitofrontal cortex and amygdalo-hippocampal complex independently explain variability in euphoric experience and that medial orbitofrontal cortex volume, in conjunction with other structures within the mOFC-centered corticolimbic circuit, can be used to predict individuals' euphoric experience.

Association between nicotine withdrawal and reward responsiveness in humans and rats

IMPORTANCE

Reward-related disturbances after withdrawal from nicotine are hypothesized to contribute to relapse to tobacco smoking but mechanisms underlying and linking such processes remain largely unknown.

OBJECTIVE

To determine whether withdrawal from nicotine affects reward responsiveness (ie, the propensity to modulate behavior as a function of prior reinforcement experience) across species using translational behavioral assessments in humans and rats.

DESIGN, SETTING, PARTICIPANTS

Experimental studies used analogous reward responsiveness tasks in both humans and rats to examine whether reward responsiveness varied in (1) an ad libitum smoking condition compared with a 24-hour acute nicotine abstinence condition in 31 human smokers with (n = 17) or without (n = 14) a history of depression; (2) rats 24 hours after withdrawal from chronic nicotine (n = 19) or saline (n = 20); and (3) rats following acute nicotine exposure after withdrawal from either chronic nicotine or saline administration.

MAIN OUTCOMES AND MEASURES

Performance on a reward responsiveness task under nicotine and nonnicotine conditions.

RESULTS

In both human smokers and nicotine-treated rats, reward responsiveness was significantly reduced after 24-hour withdrawal from nicotine (P < .05). In humans, withdrawal-induced deficits in reward responsiveness were greater in those with a history of depression. In rats previously exposed to chronic nicotine, acute nicotine reexposure long after withdrawal potentiated reward responsiveness (P < .05).

CONCLUSIONS AND RELEVANCE

These findings across species converge in suggesting that organisms have diminished ability to modulate behavior as a function of reward during withdrawal of nicotine. This blunting may contribute to relapse to tobacco smoking, particularly in depression-vulnerable individuals, to reinstate responsiveness to natural rewards and to experience potentiated nicotine-induced reward responsiveness. Moreover, demonstration of behavioral homology across humans and rodents provides a strong translational framework for the investigation and development of clinical treatments targeting reward responsiveness deficits during early withdrawal of nicotine.

Nicotine differentially modulates antisaccade eye-gaze away from emotional stimuli in nonsmokers stratified by pre-task baseline performance

RATIONALE AND OBJECTIVE

Studies indicate that nicotine enhances some aspects of attention and executive functioning and attenuates the attentional salience of emotionally negative distractors. The purpose of this study was to assess whether nicotine can enhance executive control over prepotent responses in emotional contexts in nonsmokers and whether such enhancement is greater in individuals with low baseline performance (BP).

METHODS

The antisaccade task (AST) measures the inhibition of the tendency to glance in the direction of the onset of a visual stimulus and thus is an index of control over prepotent responses. Ten male and 14 female nonsmokers wore nicotine and placebo patches on counterbalanced days that included emotional picture primes and targets.

RESULTS

There were significant beneficial effects of nicotine on antisaccade reaction time (RT). These beneficial effects occurred in individuals with poor and average BP, but not in high baseline performers. In slow baseline RT individuals, nicotine reduced RTs associated with negative targets in the left visual field (VF) and reduced RTs associated with positive and neutral targets in the right VF. In contrast, in the average baseline group, nicotine reduced RTs for positive targets in both VFs and neutral targets in the left VF.

CONCLUSIONS

The results suggest that nicotine may produce its effects by enhancing executive functions and that the differential effects as a function of VF, target emotion, and group may also reflect lateralized differences in the effects of nicotine on brain reactivity to emotional stimuli.

Effects of nicotine on electroencephalography and affect in adolescent females with major depressive disorder: a pilot study

BACKGROUND

Given that smoking is typically initiated during adolescence, and that this period in brain development seems to be uniquely sensitive to nicotine, depressed youth may be most susceptible to the neuromodulatory and mood-altering effects of nicotine. Electroencephalographic (EEG) studies suggest that individuals with major depressive disorder (MDD) exhibit left frontal lobe hypoactivation (indexed by increased EEG alpha), a region implicated in positive affect regulation, as well as right parietal hypoactivation. Smoking/nicotine abstinence has been associated with increased left frontal and right parietal alpha activity (reduced activation), which has been correlated with increased depression ratings; nicotine administration seems to normalize this depression-associated asymmetry.

OBJECTIVES

This pilot study investigated whether acute nicotine administration in adolescent female smokers with MDD would alter resting EEG activity and affect.

METHODS

Subjective mood ratings and EEG recordings were acquired before and 2 hours after administering a transdermal placebo or nicotine (21 mg) patch to 8 adolescent female smokers with MDD.

RESULTS

Nicotine induced a modest increase in alpha1 amplitude in the right hemisphere and simultaneously decreased left-favoring alpha1 amplitude asymmetry. It also attenuated left alpha1 and alpha2 amplitude in the central region. Consistent with nicotine's stimulatory action, nicotine decreased theta amplitude in the right parietal region. No accompanying mood alterations were found, although smoking withdrawal and craving as well as physical symptom scores were reduced with nicotine.

CONCLUSIONS

The results of this pilot study, the first to examine the electrocortical effects of nicotine in depressed adolescents, indicate that nicotine modulates EEG asymmetry measures, laying the stage for further research regarding the role of nicotine on affective neurocircuitry in this population.

The influence of tobacco consumption on the relationship between schizotypy and hemispheric asymmetry

Tobacco use is positively associated with severity of symptoms along the schizophrenia spectrum. Accordingly it could be argued that neuropsychological performance, formerly thought to be modulated by schizotypy, is actually modulated by drug use or an interaction of drug use and schizotypy. We tested whether habitual cigarette smokers as compared to non-smokers would show a neuropsychological profile similar to that observed along the schizophrenia spectrum and, if so, whether smoking status or nicotine dependence would be more significant modulators of behavior than schizotypy. Because hemispheric dominance has been found to be attenuated along the schizophrenia spectrum, 40 right-handed male students (20 non-smokers) performed lateralized left- (lexical decisions) and right- (facial decision task) hemisphere dominant tasks. All individuals completed self-report measures of schizotypy and nicotine dependence. Schizotypy predicted laterality in addition to smoking status: While positive schizotypy (Unusual Experiences) was unrelated to hemispheric performance, Cognitive Disorganization predicted reduced left hemisphere dominant language functions. These latter findings suggest that Cognitive Disorganization should be regarded separately as a potentially important mediator of thought disorganization and language processing. Additionally, increasing nicotine dependence among smokers predicted a right hemisphere shift of function in both tasks that supports the role of the right hemisphere in compulsive/impulsive behavior.

Nicotine primes attention to competing affective stimuli in the context of salient alternatives

Despite the importance of the subject, the effects of nicotine on the interplay between affect and attentional bias are not clear. This interplay was assessed with a novel design of the Primed Attentional Competition Task (PACT). It included a 200-ms duration emotional priming picture (negative, positive, or neutral) followed by a dual-target picture of two emotional faces side-by-side. A second task included an emotional priming picture followed by a single emotional target picture in a classic affective priming (CAP) task, assessing reaction time to identify the valence. Smokers completed the tasks in a double-blind repeated measures design wearing a nicotine patch on one day and a placebo patch on the other day. Consistent with hypotheses, nicotine enhanced the effectiveness of positive primes to bias first gaze-fixations (FGFs) toward neutral pictures relative to negative pictures and attenuated the effectiveness of negative primes on FGFs toward negative pictures, but did not bias performance in the CAP task where competing target stimuli were not present. These effects of nicotine on affective priming and attentional bias toward competing reinforcers may contribute to smoking motivation.

Effects of nicotine on novelty detection and memory recognition performance: double-blind, placebo-controlled studies of smokers and nonsmokers

RATIONALE

Dependent smokers exhibit deficits in attentional and memory processes when smoking abstinent as compared to when satiated. While nicotine replacement therapy improves attention during abstinence, it is unclear whether this is due to the alleviation of withdrawal-related deficits or inherent beneficial effects of nicotine.

OBJECTIVES

The primary aim of these studies was to test whether nicotine exerts a beneficial effect on novelty detection and whether such effects occur in nonsmokers as well as habitual smokers.

MATERIALS AND METHODS

In two parallel, double-blind, placebo-controlled studies, 24 smokers (study 1) and 24 nonsmokers (study 2) were tested in two counterbalanced sessions: once while wearing a nicotine patch (smokers = 14 mg; nonsmokers = 7 mg) and once while wearing a placebo patch. On each day, participants performed three content-specific oddball tasks (perceptual, semantic, and emotional) that required them to press a button whenever they saw a novel target (20% of stimuli) embedded in a stream of common nontarget stimuli (80% of stimuli). Recognition memory for targets was subsequently tested. Reports of mood, smoking withdrawal, patch side effects, and blind success were collected in each session.

RESULTS

Among smokers, compared to placebo, nicotine decreased target reaction time during all oddball tasks. Among nonsmokers, nicotine increased target detection accuracy and subsequent memory recognition. Nicotine's enhancement on each respective measure was not task-content specific in either sample.

CONCLUSIONS

These data suggest that acute nicotine administration may exert direct beneficial effects on novelty detection and subsequent memory recognition in both smokers and nonsmokers. Moreover, these effects are not content-specific.