Memory retrieval of smoking-related images induce greater insula activation as revealed by an fMRI-based delayed matching to sample task

Acute Stress Enhances Memory and Preference for Smoking-Related Associations in Smokers

INTRODUCTION

Nicotine dependence follows a chronic course that is characterized by repeated relapse, often driven by acute stress and rewarding memories of smoking retrieved from related contexts. These two triggers can also interact, with stress influencing retrieval of contextual memories. However, the roles of these processes in nicotine dependence remain unknown.

AIMS AND METHODS

We investigated how acute stress biases memory for smoking-associated contexts among smokers (N = 65) using a novel laboratory paradigm. On day 1, participants formed associations between visual stimuli of items (either neutral or related to smoking) and places (background scenes). On day 2 (24 hours later), participants were exposed to an acute laboratory-based stressor (socially evaluated cold pressor test; N = 32) or a matched control condition (N = 33) prior to being tested on their memory recognition and preferences for each item and place. We distinguished the accuracy of memory into specific (ie, precisely correct) or gist (ie, lure items with similar content) categories.

RESULTS

Results demonstrated that the stressor significantly induced physiological and subjective perceived stress responses, and that stressed smokers exhibited a memory bias in favor of smoking-related items. In addition, the stressed group displayed greater preference for both smoking-related items and places that had been paired with the smoking-related items. We also found suggestive evidence that stronger smoking-related memory biases were associated with more severe nicotine dependence (ie, years of smoking).

CONCLUSIONS

These results highlight the role of stress in biasing smokers toward remembering contexts associated with smoking, and amplifying their preference for these contexts.

IMPLICATIONS

The current study elucidates the role of acute stress in promoting memory biases favoring smoking-related associations among smokers. The results suggest that the retrieval of smoking-biased associative memory could be a crucial factor in stress-related nicotine seeking. This may lead to a potential intervention targeting the extinction of smoking-related context memories as a preventive strategy for stress-induced relapse.

Value-based cognition and drug dependency

Value-based decision-making is thought to play an important role in drug dependency. Achieving elevated levels of euphoria or ameliorating dysphoria/pain may motivate goal-directed drug consumption in both drug-naïve and long-time users. In other words, drugs become viewed as the preferred means of attaining a desired internal state. The bias towards choosing drugs may affect one's cognition. Observed biases in learning, attention and memory systems within the brain gradually focus one's cognitive functions towards drugs and related cues to the exclusion of other stimuli. In this narrative review, the effects of drug use on learning, attention and memory are discussed with a particular focus on changes across brain-wide functional networks and the subsequent impact on behaviour. These cognitive changes are then incorporated into the cycle of addiction, an established model outlining the transition from casual drug use to chronic dependency. If drug use results in the elevated salience of drugs and their cues, the studies highlighted in this review strongly suggest that this salience biases cognitive systems towards the motivated pursuit of addictive drugs. This bias is observed throughout the cycle of addiction, possibly contributing to the persistent hold that addictive drugs have over the dependent. Taken together, the excessive valuation of drugs as the preferred means of achieving a desired internal state affects more than just decision-making, but also learning, attentional and mnemonic systems. This eventually narrows the focus of one's thoughts towards the pursuit and consumption of addictive drugs.

Identifying neural signatures of tobacco retail outlet exposure: Preliminary validation of a "community neuroscience" paradigm

An extensive epidemiological literature indicates that increased exposure to tobacco retail outlets (TROs) places never smokers at greater risk for smoking uptake and current smokers at greater risk for increased consumption and smoking relapse. Yet research into the mechanisms underlying this effect has been limited. This preliminary study represents the first effort to examine the neurobiological consequences of exposure to personally relevant TROs among both smokers (n = 17) and nonsmokers (n = 17). Individuals carried a global positioning system (GPS) tracker for 2 weeks. Traces were used to identify TROs and control outlets that fell inside and outside their ideographically defined activity space. Participants underwent functional MRI (fMRI) scanning during which they were presented with images of these storefronts, along with similar store images from a different county and rated their familiarity with these stores. The main effect of activity space was additive with a Smoking status × Store type interaction, resulting in smokers exhibiting greater neural activation to TROs falling inside activity space within the parahippocampus, precuneus, medial prefrontal cortex, and dorsal anterior insula. A similar pattern was observed for familiarity ratings. Together, these preliminary findings suggest that the otherwise distinct neural systems involved in self-orientation/self-relevance and smoking motivation may act in concert and underlie TRO influence on smoking behavior. This study also offers a novel methodological framework for evaluating the influence of community features on neural activity that can be readily adapted to study other health behaviors.

Identifying Individuals With Mild Cognitive Impairment Using Working Memory-Induced Intra-Subject Variability of Resting-State EEGs

Individuals with mild cognitive impairment (MCI) are at high risk of developing into dementia (e. g., Alzheimer's disease, AD). A reliable and effective approach for early detection of MCI has become a critical challenge. Although compared with other costly or risky lab tests, electroencephalogram (EEG) seems to be an ideal alternative measure for early detection of MCI, searching for valid EEG features for classification between healthy controls (HCs) and individuals with MCI remains to be largely unexplored. Here, we design a novel feature extraction framework and propose that the spectral-power-based task-induced intra-subject variability extracted by this framework can be an encouraging candidate EEG feature for the early detection of MCI. In this framework, we extracted the task-induced intra-subject spectral power variability of resting-state EEGs (as measured by a between-run similarity) before and after participants performing cognitively exhausted working memory tasks as the candidate feature. The results from 74 participants (23 individuals with AD, 24 individuals with MCI, 27 HC) showed that the between-run similarity over the frontal and central scalp regions in the HC group is higher than that in the AD or MCI group. Furthermore, using a feature selection scheme and a support vector machine (SVM) classifier, the between-run similarity showed encouraging leave-one-participant-out cross-validation (LOPO-CV) classification performance for the classification between the MCI and HC (80.39%) groups and between the AD vs. HC groups (78%), and its classification performance is superior to other widely-used features such as spectral powers, coherence, and the complexity estimated by Katz's method extracted from single-run resting-state EEGs (a common approach in previous studies). The results based on LOPO-CV, therefore, suggest that the spectral-power-based task-induced intra-subject EEG variability extracted by the proposed feature extraction framework has the potential to serve as a neurophysiological feature for the early detection of MCI in individuals.

Influence of the natural hormonal milieu on brain and behavior in women who smoke cigarettes: Rationale and methodology

Women experience more severe health consequences from smoking, have greater difficulty quitting, and respond less favorably to nicotine replacement therapy than men. The influence of fluctuating ovarian hormones, specifically estradiol (E) and progesterone (P), on brain and behavioral responses during exposure to smoking reminders (i.e., cues) may be a contributing factor. Results from our laboratory suggest that women in the late follicular phase of their menstrual cycle (MC) have enhanced smoking cue (SC) vulnerabilities and reduced functional connectivity in neurocircuitry underlying cognitive control, potentially placing them at greater risk for continued smoking and relapse. The primary aim of this study is to examine and link hormonal status with brain and behavioral responses to SCs over the course of three monthly MCs in naturally cycling women who are chronic cigarette smokers. This longitudinal, counterbalanced study collects brain and behavioral responses to SCs at three time points during a woman's MC. Participants complete psychological and physical examinations, biochemical hormonal verification visits, and at least three laboratory/neuroimaging scan visits. The scan visits include a 10-min SC task during blood oxygen level-dependent (BOLD) data acquisition and are timed to occur during the early follicular phase (low E and P), late follicular phase (high E, unopposed by P), and mid-luteal phase (high P, high E). The primary outcomes include brain responses to SCs (compared to non-SCs), subjective craving, E and P hormone levels, and behavioral responses to SCs. This study addresses a critical gap in our knowledge: namely, the impact of the natural hormonal milieu on brain and behavioral responses to SCs, a powerful relapse trigger. Additionally, this study will provide a roadmap for human sex differences researchers who are obliged to consider the often confounding cyclic hormonal fluctuations of women.

Baclofen-induced Changes in the Resting Brain Modulate Smoking Cue Reactivity: A Double-blind Placebo-controlled Functional Magnetic Resonance Imaging Study in Cigarette Smokers

Objective

Smoking cue-(SC) elicited craving can lead to relapse in SC-vulnerable individuals. Thus, identifying treatments that target SC-elicited craving is a top research priority. Reduced drug cue neural activity is associated with recovery and is marked by a profile of greater tonic (resting) activation in executive control regions, and increased connectivity between executive and salience regions. Evidence suggests the GABA-B agonist baclofen can reduce drug cue-elicited neural activity, potentially through its actions on the resting brain. Based on the literature, we hypothesize that baclofen’s effects in the resting brain can predict its effects during SC exposure.

Methods

In this longitudinal, double blind, placebo-controlled neuropharmacological study 43 non-abstinent, sated treatment-seeking cigarette smokers (63% male) participated in an fMRI resting-state scan and a SC-reactivity task prior to (T1) and 3 weeks following randomization (T2; baclofen: 80 mg/day; n = 21). Subjective craving reports were acquired before and after SC exposure to explicitly examine SC-induced craving.

Results

Whole-brain full-factorial analysis revealed a group-by-time interaction with greater resting brain activation of the right dorsolateral prefrontal cortex (dlPFC) at T2 in the baclofen group (BAC) (p_FWEcorr = 0.02), which was associated with reduced neural responses to SCs in key cue-reactive brain regions; the anterior ventral insula and ventromedial prefrontal cortex (p_FWEcorr < 0.01). BAC, but not the placebo group reported decreased SC-elicited craving (p = 0.02).

Conclusion

Results suggest that baclofen mitigates the reward response to SCs through an increase in tonic activation of the dlPFC, an executive control region. Through these mechanisms, baclofen may offer SC-vulnerable smokers protection from SC-induced relapse.

Caudate reactivity to smoking cues is associated with increased responding to monetary reward in nicotine-dependent individuals

Quitting smoking is challenging in part because environmental smoking cues can trigger the desire to smoke. Neurobiological responses to smoking cues are often observed in reward-related brain regions such as the caudate and nucleus accumbens (NAc). While reward plays a well-established role in the formation of cue reactivity, whether general reward responsiveness contributes to individual differences in cue-reactivity among chronic smokers is unclear; establishing such link could provide insight into the mechanisms maintaining cue reactivity. The current study explored this relationship by assessing smoking cue reactivity during functional magnetic imaging followed by an out-of-scanner probabilistic reward task (PRT) in 24 nicotine-dependent smokers (14 women). In addition, owing to sex differences in cue reactivity and reward function, this same relationship was examined as a function of sex. Following recent smoking, greater reward responsiveness on the PRT was associated with enhanced left caudate reactivity to smoking cues. No relationship was found in any other striatal subregion. The positive relationship between reward responsiveness and caudate smoking cue reactivity was significant only in male smokers, fitting with the idea that males and females respond to the reinforcing elements of smoking cues differently. These findings are clinically relevant as they show that, following recent smoking, nicotine-dependent individuals who are more cue reactive are also more likely to be responsive to non-drug rewards, which may be useful for making individualized treatment decisions that involve behavioral reward contingencies.

Verbal suggestions of nicotine content modulate ventral tegmental neural activity during the presentation of a nicotine-free odor in cigarette smokers

Expectancies of nicotine content have been shown to impact smokers' subjective responses and smoking behaviors. However, little is known about the neural substrates modulated by verbally induced expectancies in smokers. In this study we used functional magnetic resonance imaging (fMRI) to investigate how verbally induced expectations, regarding the presence or absence of nicotine, modulated smokers' neural response to a nicotine-free odor. While laying in the scanner, all participants (N = 24) were given a nicotine-free odor, but whereas one group was correctly informed about the absence of nicotine (control group n = 12), the other group was led to believe that the presented odor contained nicotine (expectancy group n = 12). Smokers in the expectancy group had significantly increased blood-oxygen-level-dependent (BOLD) responses during the presentation of the nicotine-free odor in the left ventral tegmental area (VTA), and in the right insula, as compared to smokers in the control group (Regions of interest analysis with pFWE-corrected p ≤ 0.05). At a more liberal uncorrected statistical level (p-unc ≤ 0.001), increased bilateral reactivity in the dorsolateral prefrontal cortex (dlPFC) was also observed in the expectancy group as compared with the control group. Our findings suggest that nicotine-expectancies induced through verbal instructions can modulate nicotine relevant brain regions, without nicotine administration, and provide further neural support for the key role that cognitive expectancies play in the cause and treatment of nicotine dependence.

Quitting starts in the brain: a randomized controlled trial of app-based mindfulness shows decreases in neural responses to smoking cues that predict reductions in smoking

Current treatments for smoking yield suboptimal outcomes, partly because of an inability to reduce cue-induced smoking. Mindfulness training (MT) has shown preliminary efficacy for smoking cessation, yet its neurobiological target remains unknown. Our prior work with nonsmokers indicates that MT reduces posterior cingulate cortex (PCC) activity. In individuals who smoke, the PCC, consistently a main hub of the "default mode network," activates in response to smoking cues. In this randomized controlled trial, we tested the effects of app-delivered MT on PCC reactivity to smoking cues and whether individual differences in MT-mediated PCC changes predicted smoking outcomes. Smoking cue-induced PCC reactivity was measured using functional magnetic resonance imaging at baseline and 1 month after receiving smartphone app-based MT (n = 33) vs. an active control (National Cancer Institute's QuitGuide, n = 34). Whether individual differences in treatment-related changes in PCC activity predicted smoking behavior was assessed. The MT group demonstrated a significant correlation between a reduction in PCC reactivity to smoking cues and a decline in cigarette consumption (r = 0.39, p = 0.02). No association was found in the control group (r = 0.08, p = 0.65). No effects of group alone were found in PCC or cigarette reduction. Post hoc analysis revealed this association is sex specific (women, r = 0.49, p = 0.03; men: r = -0.08, p = 0.79). This initial report indicates that MT specifically reduces smoking cue-induced PCC activity in a subject-specific manner, and the reduction in PCC activity predicts a concurrent decline in smoking. These findings link the hypothesized behavioral effects of MT for smoking to neural mechanisms particularly in women. This lays the groundwork for identifying individuals who may benefit from targeted digital therapeutic treatments such as smartphone-based MT, yielding improved clinical outcomes.

The Insula: A Brain Stimulation Target for the Treatment of Addiction

Substance use disorders (SUDs) are a growing public health concern with only a limited number of approved treatments. However, even approved treatments are subject to limited efficacy with high long-term relapse rates. Current treatment approaches are typically a combination of pharmacotherapies and behavioral counselling. Growing evidence and technological advances suggest the potential of brain stimulation techniques for the treatment of SUDs. There are three main brain stimulation techniques that are outlined in this review: transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS). The insula, a region of the cerebral cortex, is known to be involved in critical aspects underlying SUDs, such as interoception, decision making, anxiety, pain perception, cognition, mood, threat recognition, and conscious urges. This review focuses on both the preclinical and clinical evidence demonstrating the role of the insula in addiction, thereby demonstrating its promise as a target for brain stimulation. Future research should evaluate the optimal parameters for brain stimulation of the insula, through the use of relevant biomarkers and clinical outcomes for SUDs.

The insula in nicotine use disorder: Functional neuroimaging and implications for neuromodulation

Insula dysfunction contributes to nicotine use disorders. Yet, much remains unknown about how insular functions promote nicotine use. We review current models of brain networks in smoking and propose an extension to those models that emphasizes the role of the insula in craving. During acute withdrawal, the insula provides the sensation of craving to the cerebrum and is thought to negotiate craving sensations with cognitive control to guide behavior - either to smoke or abstain. Recent studies have shown that insula processing is saturable, such that different insular functions compete for limited resources. We propose that this saturability explains how craving during withdrawal can overload insular processing to the exclusion of other functions, such as saliency and network homeostasis. A novel signal flow model illustrates how limited insular capacity leads to breakdown of normal function. Finally, we discuss suitability of insula as a neuromodulation target to promote cessation. Given the limited efficacy of standard-of-care treatments for nicotine use disorder, insular neuromodulation offers an innovative, potentially therapeutic target for improving smoking cessation.

Different modulation effects of Tai Chi Chuan and Baduanjin on resting-state functional connectivity of the default mode network in older adults

The default mode network (DMN) plays an important role in age-related cognitive decline. This study aims to explore the modulation effect of two mind-body interventions (Tai Chi Chuan and Baduanjin) on DMN in elderly individuals. Participants between 50 and 70 years old were recruited and randomized into a Tai Chi Chuan, Baduanjin or control group. The Wechsler Memory Scale-Chinese Revision and resting-state fMRI scans were administered at baseline and following 12 weeks of exercise. Seed-based resting-state functional connectivity (rsFC) was calculated. We found that (i) compared to the Baduanjin group, Tai Chi Chuan was significantly associated with increased rsFC between the medial prefrontal cortex (mPFC) and right putamen/caudate and (ii) compared to the control group, Tai Chi Chuan increased posterior cingulate cortex rsFC with the right putamen/caudate, while Baduanjin decreased rsFC between the mPFC and orbital prefrontal gyrus/putamen. Baseline mPFC rsFC with orbital prefrontal gyrus was negatively correlated with visual reproduction subscore. These results suggest that both Tai Chi Chuan and Baduanjin can modulate the DMN, but through different pathways. Elucidating the mechanisms underlying different mind-body interventions may shed light on the development of new methods to prevent age-related diseases as well as other disorders associated with disrupted DMN.

Neural Responses to Smoking Cues in Schizophrenia

The high prevalence of nicotine dependence contributes to excess mortality in schizophrenia. Cue reactivity, or the encounter of drug-related cues or contexts, triggers craving, drug-seeking, and relapse. Prior functional magnetic resonance imaging (fMRI) research indicates that individuals with schizophrenia have blunted neural responses to rewarding stimuli in association with more severe negative symptoms. The objectives of this study are to determine if smokers with schizophrenia have altered neural reactivity to smoking cues compared with non-psychiatrically ill smokers and to evaluate the influence of negative symptoms on cue reactivity. Twenty smokers with schizophrenia and 19 control smokers underwent fMRI while viewing smoking-related and neutral cues. The primary analysis was group comparison of Smoking-Neutral contrast using whole-brain analysis (Pcorrected < .05). Smokers with schizophrenia had significantly greater baseline carbon monoxide levels and longer duration of smoking, suggesting more nicotine use. While both groups had greater brain reactivity to smoking vs neutral cues, smokers with schizophrenia had significantly decreased cue reactivity (Smoking-Neutral) compared to controls in bilateral frontal midline regions. There were significant negative correlations between negative symptoms and frontal midline reactivity. Despite greater nicotine use, smokers with schizophrenia exhibited decreased smoking cue-induced neural reactivity in frontal midline regions, suggesting that increased smoking and low cessation rates in schizophrenia are not primarily driven by responses to smoking-related cues. The finding of negative correlations between cue reactivity and negative symptoms is consistent with previous research demonstrating decreased neural responses to rewarding cues, particularly in patients with negative symptoms.

Brain substrates of early (4h) cigarette abstinence: Identification of treatment targets

INTRODUCTION

Research indicates that overnight nicotine abstinence disrupts neural activity in the mesocorticolimbic reward network; however, less is known about the time course of abstinence-induced brain changes. To examine the potential neural effects of early abstinence, we used arterial spin labeling perfusion fMRI, to measure regional cerebral blood flow (rCBF) changes in the resting brain induced by 4h of nicotine abstinence.

METHODS

In a repeated measures design, 5min of resting perfusion fMRI data were acquired in awake nicotine-dependent individuals (eyes open) during 'smoking as usual' (SMK) and following 4h of monitored nicotine abstinence (ABS) conditions (N=20). Conditions were compared using a paired t test in SPM8. Craving was assessed prior to each condition.

RESULTS

Compared to SMK, ABS significantly increased craving and reduced rCBF in select regions, including the hippocampus and ventral striatum (cluster corr, α=0.01, 943 contiguous voxels). The magnitude of the abstinence-induced change in rCBF correlated with the magnitude of the change in craving across conditions in select regions, including the medial and lateral orbitofrontal cortices and the anterior ventral insula (r values ranging from 0.59-0.74).

CONCLUSIONS

Results show that as few as 4h of abstinence can reduce resting rCBF in multiple nodes of the brain's mesocorticolimbic network, disrupting neural processing. Identifying early withdrawal treatment targets has far-reaching implications, which include thwarting relapse proclivities. Results parallel those of the extant human literature and are in agreement with an extensive preclinical literature showing compromised mesolimbic dopaminergic function and impairments in reward function during nicotine withdrawal.

Resting-State Functional Connectivity of the Basal Nucleus of Meynert in Cigarette Smokers: Dependence Level and Gender Differences

Introduction

Numerous studies have characterized impaired cerebral functioning in nicotine-addicted individuals. Whereas nicotine interacts with multiple neurotransmitters in cortical and subcortical circuits, it directly targets the cholinergic system, sourced primarily from the basal nucleus of Meynert (BNM). However, no studies have examined how this cholinergic system is influenced by cigarette smoking. Here, we addressed this gap of research.

Methods

Using a dataset from the Functional Connectome Projects, we investigated this issue by contrasting seed-based BNM connectivity of 40 current smokers and 170 age- and gender-matched nonsmokers. We followed our data analytic routines in recent work and examined differences between smokers and nonsmokers in men and women combined as well as separately.

Results

Compared to nonsmokers, female but not male smokers demonstrated greater positive BNM connectivity to the supplementary motor area, bilateral anterior insula, and right superior temporal/supramarginal gyri as well as greater negative connectivity to the posterior cingulate cortex and precuneus. Further, BNM connectivity to the supplementary motor area is negatively correlated to the Fagerström Test for Nicotine Dependence score in male but not female smokers.

Conclusions

Along with a previous report of upregulated nicotinic acetylcholine receptor in male but not female smokers, these new findings highlight functional changes of the cholinergic systems in cigarette smokers. The results suggest sex-specific differences in cholinergic dysregulation and a need for multiple imaging modalities to capture the neural markers of nicotine addiction.

Implications

Nicotine influences cognition via cholinergic projections of the basal forebrain to the cerebral cortex. This study examined changes in resting-state whole-brain functional connectivity of the BNM in cigarette smokers. The new findings elucidate for the first time sex differences in BNM-cerebral connectivity in cigarette smoking.

Investigating the neural correlates of smoking: Feasibility and results of combining electronic cigarettes with fMRI

Cigarette addiction is driven partly by the physiological effects of nicotine, but also by the distinctive sensory and behavioural aspects of smoking, and understanding the neural effects of such processes is vital. There are many practical difficulties associated with subjects smoking in the modern neuroscientific laboratory environment, however electronic cigarettes obviate many of these issues, and provide a close simulation of smoking tobacco cigarettes. We have examined the neural effects of 'smoking' electronic cigarettes with concurrent functional Magnetic Resonance Imaging (fMRI). The results demonstrate the feasibility of using these devices in the MRI environment, and show brain activation in a network of cortical (motor cortex, insula, cingulate, amygdala) and sub-cortical (putamen, thalamus, globus pallidus, cerebellum) regions. Concomitant relative deactivations were seen in the ventral striatum and orbitofrontal cortex. These results reveal the brain processes involved in (simulated) smoking for the first time, and validate a novel approach to the study of smoking, and addiction more generally.

Multi-site exploration of sex differences in brain reactivity to smoking cues: Consensus across sites and methodologies

BACKGROUND

Biological sex influences cigarette smoking behavior. More men than women smoke, but women have a harder time quitting. Sex differences in smoking cue (SC) reactivity may underlie such behavioral differences. However, the influence of sex on brain reactivity to SCs has yielded inconsistent findings suggesting the need for continued study. Here, we investigated the effect of sex on SC reactivity across two sites using different imaging modalities and SC stimulus types.

METHODS

Pseudo-continuous arterial spin-labeled (pCASL) perfusion functional magnetic resonance imaging (fMRI) was used to assess brain responses to SC versus non-SC videos in 40 smokers (23 females) at the University of Pennsylvania. BOLD fMRI was used to assess brain responses to SC versus non-SC still images in 32 smokers (18 females) at McLean Hospital. Brain reactivity to SCs was compared between men and women and was correlated with SC-induced craving.

RESULTS

In both cohorts, males showed higher SC versus non-SC reactivity compared to females in reward-related brain regions (i.e., ventral striatum/ventral pallidum, ventral medial prefrontal cortex). Brain activation during SC versus non-SC exposure correlated positively with SC-induced subjective craving in males, but not females.

CONCLUSIONS

The current work provides much needed replication and validation of sex differences in SC-reactivity. These findings also add to a body of literature showing that men have greater reward-related brain activation to drug cues across drug classes. Such sex differences confirm the need to consider sex not only when evaluating SC-reactivity but when examining nicotine dependence etiology and treatment.

Effect of Selective Inhibition of Reactivated Nicotine-Associated Memories With Propranolol on Nicotine Craving

IMPORTANCE

A relapse into nicotine addiction during abstinence often occurs after the reactivation of nicotine reward memories, either by acute exposure to nicotine (a smoking episode) or by smoking-associated conditioned stimuli (CS). Preclinical studies suggest that drug reward memories can undergo memory reconsolidation after being reactivated, during which they can be weakened or erased by pharmacological or behavioral manipulations. However, translational clinical studies using CS-induced memory retrieval-reconsolidation procedures to decrease drug craving reported inconsistent results.

OBJECTIVE

To develop and test an unconditioned stimulus (UCS)-induced retrieval-reconsolidation procedure to decrease nicotine craving among people who smoke.

DESIGN, SETTING, AND PARTICIPANTS

A translational rat study and human study in an academic outpatient medical center among 96 male smokers (aged 18- 45 years) to determine the association of propranolol administration within the time window of memory reconsolidation (after retrieval of the nicotine-associated memories by nicotine UCS exposure) with relapse to nicotine-conditioned place preference (CPP) and operant nicotine seeking in rats, and measures of preference to nicotine-associated CS and nicotine craving among people who smoke.

INTERVENTION

The study rats were injected noncontingently with the UCS (nicotine 0.15 mg/kg, subcutaneous) in their home cage, and the human study participants administered a dose of propranolol (40 mg, per os; Zhongnuo Pharma).

MAIN OUTCOMES AND MEASURES

Nicotine CPP and operant nicotine seeking in rats, and preference and craving ratings for newly learned and preexisting real-life nicotine-associated CS among people who smoke.

RESULTS

Sixty-nine male smokers completed the experiment and were included for statistical analysis: 24 in the group that received placebo plus 1 hour plus UCS, 23 who received propranolol plus 1 hour plus UCS, and 22 who received UCS plus 6 hours plus propranolol. In rat relapse models, propranolol injections administered immediately after nicotine UCS-induced memory retrieval inhibited subsequent nicotine CPP and operant nicotine seeking after short (CPP, d = 1.72, 95% CI, 0.63-2.77; operant seeking, d = 1.61, 95% CI, 0.59-2.60) or prolonged abstinence (CPP, d = 1.46, 95% CI, 0.42-2.47; operant seeking: d = 1.69, 95% CI, 0.66-2.69), as well as nicotine priming-induced reinstatement of nicotine CPP (d = 1.28, 95% CI, 0.27-2.26) and operant nicotine seeking (d = 1.61, 95% CI, 0.59-2.60) after extinction. Among the smokers, oral propranolol administered prior to nicotine UCS-induced memory retrieval decreased subsequent nicotine preference induced by newly learned nicotine CS (CS1, Cohen d = 0.61, 95% CI, 0.02-1.19 and CS2, d = 0.69, 95% CI, 0.10-1.28, respectively), preexisting nicotine CS (d = 0.57, 95% CI, -0.02 to 1.15), and nicotine priming (CS1, d = 0.82, 95% CI, 0.22-1.41 and CS2, d = 0.78, 95% CI, 0.18-1.37, respectively; preexisting nicotine CS, d = 0.92, 95% CI, 0.31-1.52), as well as nicotine craving induced by the preexisting nicotine CS (d = 0.64, 95% CI, 0.05-1.22), and nicotine priming (d = 1.15, 95% CI, 0.52-1.76).

CONCLUSIONS AND RELEVANCE

In rat-to-human translational study, a novel UCS-induced memory retrieval-reconsolidation interference procedure inhibited nicotine craving induced by exposure to diverse nicotine-associated CS and nicotine itself. This procedure should be studied further in clinical trials.

Dorsal anterior cingulate glutamate is associated with engagement of the default mode network during exposure to smoking cues

BACKGROUND

When exposed to smoking cues, nicotine dependent individuals activate brain regions overlapping with the default mode network (DMN), a network of regions involved in internally-focused cognition. The salience network (SN), which includes the dorsal anterior cingulate cortex (dACC), is thought to interact with the DMN and aids in directing attention toward salient internal or external stimuli. One possibility is that neurochemical variation in SN regions such as the dACC impact DMN reactivity to personally relevant stimuli such as smoking cues. This is consistent with emerging evidence suggesting an association between midline cortical glutamate (Glu) and activity in brain regions overlapping with the DMN.

METHODS

In 18 nicotine-dependent individuals, we assessed the relationship between DMN activation to smoking relative to neutral cues using functional magnetic resonance imaging and dACC Glu as measured by magnetic resonance spectroscopy. This association also was tested in a replication sample of 14 nicotine-dependent participants.

RESULTS

Not only was the DMN significantly less suppressed during smoking cue exposure, but also there was a positive association between DMN reactivity to smoking relative to neutral cues and dACC Glu (r=0.56, p<0.02). This finding was confirmed in the independent replication cohort (r=0.64, p<0.02).

CONCLUSIONS

The current findings confirm that the DMN is less suppressed when smokers view smoking relative to neutral cues, suggesting that smoking cues engage self-relevant processing. Furthermore, these results indicate that dACC Glu is associated with enhanced DMN engagement when nicotine-dependent individuals are exposed to self-relevant smoking cues.

Advances in nicotine research in Addiction Biology

The aim of Addiction Biology is to advance our understanding of the action of drugs of abuse and addictive processes via the publication of high-impact clinical and pre-clinical findings resulting from behavioral, molecular, genetic, biochemical, neurobiological and pharmacological research. As of 2013, Addiction Biology is ranked number 1 in the category of Substance Abuse journals (SCI). Occasionally, Addiction Biology likes to highlight via review important findings focused on a particular topic and recently published in the journal. The current review summarizes a number of key publications from Addiction Biology that have contributed to the current knowledge of nicotine research, comprising a wide spectrum of approaches, both clinical and pre-clinical, at the cellular, molecular, systems and behavioral levels. A number of findings from human studies have identified, using imaging techniques, alterations in common brain circuits, as well as morphological and network activity changes, associated with tobacco use. Furthermore, both clinical and pre-clinical studies have characterized a number of mechanistic targets critical to understanding the effects of nicotine and tobacco addiction. Together, these findings will undoubtedly drive future studies examining the dramatic impact of tobacco use and the development of treatments to counter nicotine dependence.

Insula-Dorsal Anterior Cingulate Cortex Coupling is Associated with Enhanced Brain Reactivity to Smoking Cues

The insula plays a critical role in maintaining nicotine dependence and reactivity to smoking cues. More broadly, the insula and the dorsal anterior cingulate cortex (dACC) are key nodes of the salience network (SN), which integrates internal and extrapersonal information to guide behavior. Thus, insula-dACC interactions may be integral in processing salient information such as smoking cues that facilitate continued nicotine use. We evaluated functional magnetic resonance imaging (fMRI) data from nicotine-dependent participants during rest, and again when they viewed smoking-related images. Greater insula-dACC coupling at rest was significantly correlated with enhanced smoking cue-reactivity in brain areas associated with attention and motor preparation, including the visual cortex, right ventral lateral prefrontal cortex, and the dorsal striatum. In an independent cohort, we found that insula-dACC connectivity was stable over 1-h delay and was not influenced by changes in subjective craving or expired carbon monoxide, suggesting that connectivity strength between these regions may be a trait associated with heightened cue-reactivity. Finally, we also showed that insula reactivity to smoking cues correlates with a rise in cue-reactivity throughout the entire SN, indicating that the insula's role in smoking cue-reactivity is not functionally independent, and may actually represent the engagement of the entire SN. Collectively, these data provide a more network-level understanding of the insula's role in nicotine dependence and shows a relationship between inherent brain organization and smoking cue-reactivity.

Measuring cigarette smoking-induced cortical dopamine release: A [¹¹C]FLB-457 PET study

Striatal dopamine (DA) is thought to have a fundamental role in the reinforcing effects of tobacco smoking and nicotine. Microdialysis studies indicate that nicotine also increases DA in extrastriatal brain areas, but much less is known about its role in addiction. High-affinity D2/3 receptor radiotracers permit the measurement of cortical DA in humans using positron emission tomography (PET). [(11)C]FLB-457 PET scans were conducted in 10 nicotine-dependent daily smokers after overnight abstinence and reinstatement of smoking. Voxel-wise [(11)C]-FLB-457-binding potential (BPND) in the frontal lobe, insula, and limbic regions was estimated in the two conditions. Paired t-tests showed BPND values were reduced following smoking (an indirect index of DA release). The overall peak t was located in the cingulate gyrus, which was part of a larger medial cluster (BPND change -12.1±9.4%) and this survived false discovery rate correction for multiple comparisons. Clusters were also identified in the left anterior cingulate cortex/medial frontal gyrus, bilateral prefrontal cortex (PFC), bilateral amygdala, and the left insula. This is the first demonstration of tobacco smoking-induced cortical DA release in humans; it may be the result of both pharmacological (nicotine) and non-pharmacological factors (tobacco cues). Abstinence increased craving but had minimal cognitive effects, thus limiting correlation analyses. However, given that the cingulate cortex, PFC, insula, and amygdala are thought to have important roles in tobacco craving, cognition, and relapse, these associations warrant investigation in a larger sample. [(11)C]FLB-457 PET imaging may represent a useful tool to investigate individual differences in tobacco addiction severity and treatment response.

Influence of menstrual cycle phase on neural and craving responses to appetitive smoking cues in naturally cycling females

INTRODUCTION

Functional magnetic resonance imaging (fMRI) has been used extensively in an attempt to understand brain vulnerabilities that mediate maladaptive responses to drug cues. Using perfusion fMRI, we have consistently shown reward-related activation (medial orbitofrontal cortex/ventral striatum) to smoking cues (SCs). Because preclinical and clinical studies generally show that progesterone may reduce reward and craving, we hypothesized that females in the follicular phase of the cycle (FPs; when progesterone levels are low) would have greater reward-related neural responses to SCs compared with females in the luteal phase (LPs).

METHODS

Sated cigarette-dependent premenopausal naturally cycling females underwent pseudo-continuous arterial spin-labeled perfusion fMRI during exposure to 10-min audio visual clips of appetitive SCs and non-SCs. Brain responses to SCs relative to non-SCs were examined among females grouped according to menstrual cycle (MC) phase at the time of scanning (22 FPs, 15 LPs). Craving scores were acquired pre- and post-SC exposure.

RESULTS

FPs showed increased neural responses to SCs compared with non-SCs in the medial orbitofrontal cortex (p ≤ .05 corrected), whereas LPs did not. FPs reported SC-elicited craving (p ≤ .005), whereas LPs did not. Within FPs, SC-induced craving correlated with increased neural responses in the anterior insula (r = 0.73, p < .0001).

CONCLUSIONS

FPs may be more vulnerable to relapse during appetitive SC exposure than LPs. Because the influence of MC phase on drug cue neural activity has not been examined, these results contribute to our knowledge of the neurobiological underpinnings of responses to drug cues, and they highlight the importance of monitoring menstrual cycle phase in all areas of addiction research.

Striatal morphology is associated with tobacco cigarette craving

The striatum has a clear role in addictive disorders and is involved in drug-related craving. Recently, enhanced striatal volume was associated with greater lifetime nicotine exposure, suggesting a bridge between striatal function and structural phenotypes. To assess this link between striatal structure and function, we evaluated the relationship between striatal morphology and this brain region's well-established role in craving. In tobacco smokers, we assessed striatal volume, surface area, and shape using a new segmentation methodology coupled with local shape indices. Striatal morphology was then related with two measures of craving: state-based craving, assessed by the brief questionnaire of smoking urges (QSU), and craving induced by smoking-related images. A positive association was found between left striatal volume and surface area with both measures of craving. A more specific relationship was found between both craving measures and the dorsal, but not in ventral striatum. Evaluating dorsal striatal subregions showed a single relationship between the caudate and QSU. Although cue-induced craving and the QSU were both associated with enlarged striatal volume and surface area, these measures were differentially associated with global or more local striatal volumes. We also report a connection between greater right striatal shape deformations and cue-induced craving. Shape deformations associated with cue-induced craving were specific to striatal subregions involved in habitual responding to rewarding stimuli, which is relevant given the habitual nature of cue-induced craving. The current findings confirm a relationship between striatal function and morphology and suggest that variation in striatal morphology may be a biomarker for craving severity.