Cue reactivity in cocaine-dependent subjects: effects of cue type and cue modality

The impacts of caffeine administration, expectancies, and related stimuli on coffee craving, withdrawal, and self-administration

BACKGROUND

Caffeine is the most commonly consumed psychoactive substance, yet its potential reinforcing properties have been understudied.

AIMS

This study examined the impact of caffeine administration and expectancy on coffee-related craving, withdrawal, and cue reactivity via a balanced-placebo design.

METHODS

Following 18-h caffeine abstinence, 65 daily coffee consumers (54% male) received either caffeine-containing (100 mg) or placebo gum, along with either accurate or inaccurate information regarding the gum's caffeine content. Participants were exposed to neutral and coffee-related stimuli using different sensory modalities (visual and combined auditory/olfactory). Craving, withdrawal, and heart rate were assessed at baseline and after each cue presentation. Following the cue-reactivity assessments, participants were provided with an opportunity to self-administer units of coffee.

RESULTS

Caffeine expectancy was associated with reduced subjective withdrawal 30 min following the gum administration but was not significantly impacted by actual caffeine administration. The presentation of coffee-related cues was found to increase self-reported craving and heart rate, regardless of the expectation that caffeine had been administered. Visual, but not auditory/olfactory, cue reactivity appeared blunted when participants received a prior dose of caffeine. Prior caffeine ingestion also reduced the probability of subsequent coffee self-administration.

CONCLUSION

To our knowledge, this is the first examination of the impact of caffeine administration and expectancy on cue-elicited coffee craving and coffee consumption. Although there was some evidence that caffeine expectancy and administration were found to impact subjective withdrawal and self-administration respectively, neither was found to exert strong consistent effects on cue reactivity.

The Effects of Immediate vs Gradual Reduction in Nicotine Content of Cigarettes on Smoking Behavior: An Ecological Momentary Assessment Study

BACKGROUND

In recent years, much research has examined the effects of various interventions and treatments for smoking cessation. The results suggest that interventions targeting changes of nicotine content can help smokers reduce tobacco use or quit smoking. A number of clinical studies show that smokers who received an immediate reduction in nicotine content to very low levels have significantly greater reductions in the number of cigarettes smoked and toxic substance exposure compared to those with gradual reductions. However, from the perspective of smoking craving, whether the immediate and gradual reduction in nicotine content reduce smoking by reducing cravings needs further investigation.

METHODS

74 eligible Participants were randomly allocated to one of the two experimental conditions: (1) immediate reduction to 0.1 mg of nicotine per cigarette (n = 40); (2) gradual reduction from 1.0 (0.8 g ~ 1.2 mg) to 0.1 mg of nicotine per cigarette (n = 34). All participants completed 1-week baseline period during which they smoked their usual cigarette, followed by 16-week of interventions. The primary outcomes included cigarette cravings and number of cigarettes smoked per day (CPD); secondary outcomes included the number of cigarette-free day and emotional states.

RESULTS

Among the 52 participants [51 (98.1%) men; mean (SD) age, 33.44 (6.71) years; mean (SD) CPD, 16.83 (9.94)] who completed the trial, significantly lower cravings for cigarettes were observed in the immediate (n = 25) vs. gradual nicotine reduction group (n = 27) in the morning (t = -2.072, p = 0.039) and after dinner (t = -2.056, p = 0.041). Compared with the baseline daily smoking, the number of cigarettes smoked per day was significantly reduced at the beginning of week 12 in the immediate nicotine reduction group (p = 0.001) and at week 16 in the gradual nicotine reduction group (p < 0.001). The number of participants with any cigarette-free day was not significantly different between the groups (p = 0.198). The number of cigarette-free days was significantly more in the immediate vs. gradual nicotine reduction group (p = 0.027).

CONCLUSIONS

The significantly lower cravings were observed in the immediate vs. gradual nicotine reduction group, and led to faster reduction in the number of CPD, and a significant increase in the number of cigarette-free days. These findings add to the evidence base for reduced nicotine content in cigarettes.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier: ChiCTR2100048216.

Assessing methamphetamine-related cue reactivity in people with methamphetamine use disorder relative to controls

Methamphetamine use disorder involves methamphetamine-related cues invoking intense craving leading to relapse. Such cue reactivity is thought to arise from Pavlovian conditioning that occurs during the drug-taking experience. Cue reactivity then should be selective to methamphetamine cues (and not other cues), and not observed in people who have never experienced methamphetamine. However, these premises have never been tested and reported using objective measures such as skin conductance response (SCR). The primary aim of this study was to test these premises using a cue reactivity paradigm we developed using control cues. The secondary aim was to explore the relationship between cue reactivity, drug use characteristics, and cognition. Thirty people with a current diagnosis of methamphetamine use disorder and 30 matched controls with no history of substance use disorder were recruited. We observed higher overall subjective reactivity (F = 62.810; p < 0.001) and cue-selective physiological reactivity (F = 5.160; p = 0.026) in people with methamphetamine use disorder but not in controls. Co-morbid sedative use was associated with higher subjective craving (r = 0.521; p = 0.003). People who use methamphetamine intravenously had higher cue-selective SCR than smokers (t = 3.750; p < 0.001). Low inhibitory control measured by the Stroop task was associated with increased craving across the cue paradigm (r = -0.494; p = 0.006). Overall, these results support that cue reactivity in people with methamphetamine use disorder is due to Pavlovian conditioning. Its association with drug use and cognition highlights cue reactivity paradigm's utility in understanding methamphetamine use disorder to develop new treatments targeting cue-induced craving.

Disrupted prefrontal regulation of striatum-related craving in Internet gaming disorder revealed by dynamic causal modeling: results from a cue-reactivity task

BACKGROUND

Studies of Internet gaming disorder (IGD) suggest an imbalanced relationship between cognitive control and reward processing in people with IGD. However, it remains unclear how these two systems interact with each other, and whether they could serve as neurobiological markers for IGD.

METHODS

Fifty IGD subjects and matched individuals with recreational game use (RGU) were selected and compared when they were performing a cue-craving task. Regions of interests [anterior cingulate cortex (ACC), lentiform nucleus] were selected based on the comparison between brain responses to gaming-related cues and neutral cues. Directional connectivities among these brain regions were determined using Bayesian estimation. We additionally examined the posterior cingulate cortex (PCC) in a separate analysis based on data implicating the PCC in craving in addiction.

RESULTS

During fixed-connectivity analyses, IGD subjects showed blunted ACC-to-lentiform and lentiform-to-ACC connectivity relative to RGU subjects, especially in the left hemisphere. When facing gaming cues, IGD subjects trended toward lower left-hemispheric modulatory effects in ACC-to-lentiform connectivity than RGU subjects. Self-reported cue-related craving prior to scanning correlated inversely with left-hemispheric modulatory effects in ACC-to-lentiform connectivity.

CONCLUSIONS

The results suggesting that prefrontal-to-lentiform connectivity is impaired in IGD provides a possible neurobiological mechanism for difficulties in controlling gaming-cue-elicited cravings. Reduced connectivity ACC-lentiform connectivity may be a useful neurobiological marker for IGD.

Taste manipulation during a food cue-reactivity task: Effects on cue-elicited food craving and subsequent food intake among individuals with overweight and obesity

Food cue-reactivity tasks are used to induce and evaluate food cravings. Extant research has implicated the role of tasting foods in heightening cue-elicited food craving. The present study was the first to evaluate a taste manipulation during a food cue-reactivity task to optimize cue-elicited craving and predict food intake. Participants with overweight/obesity (N = 35; M age = 33.46 years [SD = 13.27]; M BMI = 32.91 kg/m2 [SD = 5.34]) engaged in one laboratory session and were randomized to a 'No Taste' or 'Taste' condition. All participants reported baseline food craving and observed two types of high-calorie food cues during a cue-reactivity task: photographic and real foods. The Taste group tasted real food cues and the No Taste group did not. Cue-elicited craving was assessed after the presentation of each food cue. Calorie intake of palatable foods was subsequently measured during a bogus taste test. Results indicated that cue-elicited craving to high-calorie foods was greater for the No Taste relative to the Taste group and that calorie intake was greater for the Taste relative to the No Taste group; both effects were nonsignificant, but of medium-size. Cue-elicited craving was significantly greater following exposure to high-calorie real food cues compared to photographic food cues. Results provide initial evidence that presenting high-calorie real (vs. photographic) food cues and forgoing taste manipulation during a food cue-reactivity task may optimize cue-elicited craving, and that taste manipulation could increase subsequent food intake. Future research should be conducted to replicate findings in larger samples with greater power to detect significant effects.

The sensory features of a food cue influence its ability to act as an incentive stimulus and evoke dopamine release in the nucleus accumbens core

The sensory properties of a reward-paired cue (a conditioned stimulus; CS) may impact the motivational value attributed to the cue, and in turn influence the form of the conditioned response (CR) that develops. A cue with multiple sensory qualities, such as a moving lever-CS, may activate numerous neural pathways that process auditory and visual information, resulting in CRs that vary both within and between individuals. For example, CRs include approach to the lever-CS itself (rats that “sign-track”; ST), approach to the location of reward delivery (rats that “goal-track”; GT), or an “intermediate” combination of these behaviors. We found that the multimodal sensory features of the lever-CS were important to the development and expression of sign-tracking. When the lever-CS was covered, and thus could only be heard moving, STs not only continued to approach the lever location but also started to approach the food cup during the CS period. While still predictive of reward, the auditory component of the lever-CS was a much weaker conditioned reinforcer than the visible lever-CS. This plasticity in behavioral responding observed in STs closely resembled behaviors normally seen in rats classified as “intermediates.” Furthermore, the ability of both the lever-CS and the reward-delivery to evoke dopamine release in the nucleus accumbens was also altered by covering the lever—dopamine signaling in STs resembled neurotransmission observed in rats that normally only GT. These data suggest that while the visible lever-CS was attractive, wanted, and had incentive value for STs, when presented in isolation, the auditory component of the cue was simply predictive of reward, lacking incentive salience. Therefore, the specific sensory features of cues may differentially contribute to responding and ensure behavioral flexibility.

Cue-induced craving in patients with cocaine use disorder predicts cognitive control deficits toward cocaine cues

INTRODUCTION

Cue-induced craving is a clinically important aspect of cocaine addiction influencing ongoing use and sobriety. However, little is known about the relationship between cue-induced craving and cognitive control toward cocaine cues. While studies suggest that cocaine users have an attentional bias toward cocaine cues, the present study extends this research by testing if cocaine use disorder patients (CDPs) can control their eye movements toward cocaine cues and whether their response varied by cue-induced craving intensity.

METHODS

Thirty CDPs underwent a cue exposure procedure to dichotomize them into high and low craving groups followed by a modified antisaccade task in which subjects were asked to control their eye movements toward either a cocaine or neutral drug cue by looking away from the suddenly presented cue. The relationship between breakdowns in cognitive control (as measured by eye errors) and cue-induced craving (changes in self-reported craving following cocaine cue exposure) was investigated.

RESULTS

CDPs overall made significantly more errors toward cocaine cues compared to neutral cues, with higher cravers making significantly more errors than lower cravers even though they did not differ significantly in addiction severity, impulsivity, anxiety, or depression levels. Cue-induced craving was the only specific and significant predictor of subsequent errors toward cocaine cues.

CONCLUSION

Cue-induced craving directly and specifically relates to breakdowns of cognitive control toward cocaine cues in CDPs, with higher cravers being more susceptible. Hence, it may be useful identifying high cravers and target treatment toward curbing craving to decrease the likelihood of a subsequent breakdown in control.

Factors modulating neural reactivity to drug cues in addiction: a survey of human neuroimaging studies

Human neuroimaging studies suggest that neural cue reactivity is strongly associated with indices of drug use, including addiction severity and treatment success. However, little is known about factors that modulate cue reactivity. The goal of this review, in which we survey published fMRI and PET studies on drug cue reactivity in cocaine, alcohol, and tobacco cigarette users, is to highlight major factors that modulate brain reactivity to drug cues. First, we describe cue reactivity paradigms used in neuroimaging research and outline the brain circuits that underlie cue reactivity. We then discuss major factors that have been shown to modulate cue reactivity and review specific evidence as well as outstanding questions related to each factor. Building on previous model-building reviews on the topic, we then outline a simplified model that includes the key modulatory factors and a tentative ranking of their relative impact. We conclude with a discussion of outstanding challenges and future research directions, which can inform future neuroimaging studies as well as the design of treatment and prevention programs.

The effects of varied extinction procedures on contingent cue-induced reinstatement in Sprague-Dawley rats

RATIONALE

Cue exposure therapy, which attempts to limit relapse by reducing reactivity to cocaine-paired cues through repeated exposures, has had limited success.

OBJECTIVES

The current experiments examined cocaine cue-induced anxiogenesis and investigated whether a model of cue exposure therapy would reduce reinstatement of cocaine seeking in rats with a history of cocaine self-administration.

METHODS

Male rats experienced daily intravenous cocaine self-administration. Rats then experienced exposure to either the self-administration context or the context plus noncontingent presentations of cocaine-paired cues. Immediately following exposure, anxiety-like behavior was measured using elevated plus maze and defensive burying tests. In a second group of rats, self-administration was followed by 7 days of exposure to the context, context + noncontingent cue exposure, lever extinction, or cue + lever extinction. All animals then underwent two contingent cue-induced reinstatement tests separated by 7 days of lever extinction.

RESULTS

Exposure to noncontingent cocaine-paired cues in the self-administration context increased anxiety-like behavior on the defensive burying test. Animals that experienced lever + cue extinction displayed the least cocaine seeking on the first reinstatement test, and lever extinction reduced cocaine seeking below context exposure or context + noncontingent cue exposure. All animals had similar levels of cocaine seeking on the second reinstatement test.

CONCLUSION

Noncontingent cue exposure causes anxiety, and noncontingent cue and context exposure are less effective at reducing contingent cue-induced reinstatement than lever or lever + cue extinction. These data indicate that active extinction of the drug-taking response may be critical for reduction of relapse proclivity in former cocaine users.

Sensory modality of smoking cues modulates neural cue reactivity

RATIONALE

Behavioral experiments have demonstrated that the sensory modality of presentation modulates drug cue reactivity.

OBJECTIVES

The present study on nicotine addiction tested whether neural responses to smoking cues are modulated by the sensory modality of stimulus presentation.

METHODS

We measured brain activation using functional magnetic resonance imaging (fMRI) in 15 smokers and 15 nonsmokers while they viewed images of smoking paraphernalia and control objects and while they touched the same objects without seeing them.

RESULTS

Haptically presented, smoking-related stimuli induced more pronounced neural cue reactivity than visual cues in the left dorsal striatum in smokers compared to nonsmokers. The severity of nicotine dependence correlated positively with the preference for haptically explored smoking cues in the left inferior parietal lobule/somatosensory cortex, right fusiform gyrus/inferior temporal cortex/cerebellum, hippocampus/parahippocampal gyrus, posterior cingulate cortex, and supplementary motor area.

CONCLUSIONS

These observations are in line with the hypothesized role of the dorsal striatum for the expression of drug habits and the well-established concept of drug-related automatized schemata, since haptic perception is more closely linked to the corresponding object-specific action pattern than visual perception. Moreover, our findings demonstrate that with the growing severity of nicotine dependence, brain regions involved in object perception, memory, self-processing, and motor control exhibit an increasing preference for haptic over visual smoking cues. This difference was not found for control stimuli. Considering the sensory modality of the presented cues could serve to develop more reliable fMRI-specific biomarkers, more ecologically valid experimental designs, and more effective cue-exposure therapies of addiction.

A Feasibility Study of Virtual Reality-Based Coping Skills Training for Nicotine Dependence

OBJECTIVE

Virtual reality (VR)-based cue reactivity has been successfully used for the assessment of drug craving. Going beyond assessment of cue reactivity, a novel VR-based treatment approach for smoking cessation was developed and tested for feasibility.

METHOD

In a randomized experiment, 10-week treatment feasibility trial, 46 nicotine-dependent adults, completed the10-week program. Virtual reality skills training (VRST) combined with nicotine replacement therapy (NRT) was compared to NRT alone. Participants were assessed for smoking behavior and coping skills during, at end of treatment, and at posttreatment follow-up.

RESULTS

Smoking rates and craving for nicotine were significantly lower for the VRST group compared to NRT-only group at the end of treatment. Self-confidence and coping skills were also significantly higher for the VRST group, and number of cigarettes smoked was significantly lower, compared to the control group at follow-up.

CONCLUSIONS

Feasibility of VRST was supported in the current study.

Functional neuroimaging studies in addiction: multisensory drug stimuli and neural cue reactivity

Neuroimaging studies on cue reactivity have substantially contributed to the understanding of addiction. In the majority of studies drug cues were presented in the visual modality. However, exposure to conditioned cues in real life occurs often simultaneously in more than one sensory modality. Therefore, multisensory cues should elicit cue reactivity more consistently than unisensory stimuli and increase the ecological validity and the reliability of brain activation measurements. This review includes the data from 44 whole-brain functional neuroimaging studies with a total of 1168 subjects (812 patients and 356 controls). Correlations between neural cue reactivity and clinical covariates such as craving have been reported significantly more often for multisensory than unisensory cues in the motor cortex, insula and posterior cingulate cortex. Thus, multisensory drug cues are particularly effective in revealing brain-behavior relationships in neurocircuits of addiction responsible for motivation, craving awareness and self-related processing.

Using virtual reality to investigate complex and contextual cue reactivity in nicotine dependent problem drinkers

Alcohol and cigarette smoking frequently co-occur among adults in the U.S., resulting in a myriad of deleterious health outcomes. Cue reactivity has been posited as one factor that precludes individuals from overcoming alcohol and nicotine dependency. While cue reactivity studies have focused on the impact of proximal cues on cue reactivity, much less is known about the unique impact of complex and contextual cues. This pilot study compares nicotine and alcohol cue reactivity among a sample of nicotine dependent, daily drinkers (N=21) across neutral, party, and office courtyard virtual reality (VR) contexts embedded with proximal smoking cues to: 1) explore and compare the effects of complex nicotine cues on alcohol cross-cue reactivity between nicotine/alcohol dependent drinkers and nicotine dependent/non-alcohol dependent daily drinkers, and 2) assess the effectiveness of VR for eliciting cue-induced nicotine craving responses using complex nicotine cues. Nicotine dependent/non-alcohol dependent drinkers had significantly lower craving for alcohol in the non-alcohol congruent office courtyard VR scene and there was no difference in the alcohol-congruent party scene when compared to the alcohol dependent group, suggesting that the non-alcohol dependent daily drinking group was more likely to react to contextual cues. Consistent with prior cue reactivity studies, dependent smokers experienced significantly higher craving for nicotine in the VR smoking congruent contexts compared to the neutral contexts; however, nicotine/alcohol dependent participants did not return to baseline craving after exposure to smoking cues. These results suggest substantive differences in the ways that nicotine-dependent, daily alcohol drinkers and nicotine/alcohol dependent drinkers experience craving, whether cross-cue or traditional.

A double-blind, placebo-controlled, randomized pilot study comparing quetiapine with placebo, associated to naltrexone, in the treatment of alcohol-dependent patients

The objective of this study was to determine whether quetiapine plus naltrexone is more effective than naltrexone alone for the treatment of alcohol-dependent patients. This was a double-blind, randomized clinical trial where eligible alcohol-dependent patients were randomized to receive naltrexone (50mg/day) plus quetiapine (25-200mg/day) or naltrexone (50mg/day) plus placebo for 12 weeks, and afterwards patients received naltrexone alone during 4 additional weeks. The primary efficacy measures were percent days abstinent, drinks per drinking day, and the relapse rate. Sixty-two patients received a single-blind treatment with placebo plus naltrexone, and they were thereafter randomly assigned to quetiapine plus naltrexone (n=30) or placebo plus naltrexone (n=32). Eleven (36.7%) patients in the quetiapine-treated group and 4 (12.5%) patients in the placebo-treated group withdrew before they completed 12 weeks of treatment. There were no statistically significant differences for any primary drinking outcomes between treatment groups. Both regimens were well tolerated. This study failed to demonstrate any additional benefit from the combination of quetiapine and naltrexone compared to naltrexone alone on drinking outcomes.

Neurofeedback Effects on Evoked and Induced EEG Gamma Band Reactivity to Drug-related Cues in Cocaine Addiction

INTRODUCTION: Preoccupation with drug and drug-related items is a typical characteristic of cocaine addicted individuals. It has been shown in multiple accounts that prolonged drug use has a profound effect on the EEG recordings of drug addicts when compared to controls during cue reactivity tests. Cue reactivity refers to a phenomenon in which individuals with a history of drug abuse exhibit excessive psychophysiological responses to cues associated with their drug of choice. One of the aims of this pilot study was to determine the presence of an attentional bias to preferentially process drug-related cues using evoked and induced gamma reactivity measures in cocaine addicts before and after biobehavioral treatment based on neurofeedback. Another aim was to show that central SMR amplitude increase and frontal theta control is possible in an experimental outpatient drug users group over 12 neurofeedback sessions. METHOD: Ten current cocaine abusers participated in this pilot research study using neurofeedback combined with Motivational Interviewing sessions. Eight of them completed all planned pre- and post -neurofeedback cue reactivity tests with event-related EEG recording and clinical evaluations. Cue reactivity test represented a visual oddball task with images from the International Affective Picture System and drug-related pictures. Evoked and induced gamma responses to target and non-target drug cues were analyzed using wavelet analysis. RESULTS: Outpatient subjects with cocaine addiction completed the biobehavioral intervention and successfully increased SMR while keeping theta practically unchanged in 12 sessions of neurofeedback training. The addition of Motivational Interviewing helped retain patients in the study. Clinical evaluations immediately after completion of the treatment showed decreased self-reports on depression and stress scores, and urine tests collaborated reports of decreased use of cocaine and marijuana. Effects of neurofeedback resulted in a lower EEG gamma reactivity to drug-related images in a post-neurofeedback cue reactivity test. In particular, evoked gamma showed decreases in power to non-target and to a lesser extent target drug-related cues at all topographies (left, right, frontal, parietal, medial, inferior); while induced gamma power decreased globally to both target and non-target drug cues. Our findings supported our hypothesis that gamma band cue reactivity measures are sufficiently sensitive functional outcomes of neurofeedback treatment. Both evoked and induced gamma measures were found capable to detect changes in responsiveness to both target and non-target drug cues. CONCLUSION: Our study emphasizes the utility of cognitive neuroscience methods based on EEG gamma band measures for the assessment of the functional outcomes of neurofeedback-based biobehavioral interventions for cocaine use disorders. This approach may have significant potential for identifying both physiological and clinical markers of treatment progress. The results confirmed our prediction that EEG changes achieved with neurofeedback training will be accompanied by positive EEG outcomes in a cue reactivity and clinical improvements.

Reactivity to cannabis cues in virtual reality environments

Virtual reality (VR) cue environments have been developed and successfully tested in nicotine, cocaine, and alcohol abusers. Aims in the current article include the development and testing of a novel VR cannabis cue reactivity assessment system. It was hypothesized that subjective craving levels and attention to cannabis cues would be higher in VR environments with cannabis cues compared to VR neutral environments. Twenty nontreatment-seeking current cannabis smokers participated in the VR cue trial. During the VR cue trial, participants were exposed to four virtual environments that contained audio, visual, olfactory, and vibrotactile sensory stimuli. Two VR environments contained cannabis cues that consisted of a party room in which people were smoking cannabis and a room containing cannabis paraphernalia without people. Two VR neutral rooms without cannabis cues consisted of a digital art gallery with nature videos. Subjective craving and attention to cues were significantly higher in the VR cannabis environments compared to the VR neutral environments. These findings indicate that VR cannabis cue reactivity may offer a new technology-based method to advance addiction research and treatment.

Forced abstinence model of relapse to study pharmacological treatments of substance use disorder

Understanding and preventing relapse to drug use is one of the most difficult challenges faced by clinicians and practitioners in the struggle to help people remain abstinent. In this paper, we review basic preclinical research on forced abstinence periods that identify the neural substrates involved and neural adaptations that occur after a drug-free period. Our attention focuses on forced abstinence after self-administration because of its promise for translational research in the development of candidate medications to reduce relapse. This model requires subjects (often rats) to initially acquire drug self-administration. However, rather than extinguishing behavior with daily drug-free sessions as in the reinstatement model of drug seeking, subjects are removed from the self-administration situation and do not receive any exposure to the drug. Notably, the integrity of the drug-taking behavior and the drug-associated cues in the drug-taking environment are preserved because they are not experienced in the absence of the drug. Research shows time dependent increases in drug-seeking following forced abstinence periods. More so, neural substrates and adaptations within the mesocorticolimbic system and the nigrostriatal system have been identified that contribute to increased drug seeking following abstinence. From a translational perspective, behavioral and pharmacological treatment of substance use disorder often starts during this initial abstinence period (either forced or voluntary). The forced abstinence model simulates some of the features of this treatment situation and thus allows for the study of potential treatments that alter relapse of drug-seeking behaviors along with the accompanying neurobiological changes.

Intermediate cannabis dependence phenotypes and the FAAH C385A variant: an exploratory analysis

RATIONALE

Cannabis dependence is a growing problem among individuals who use marijuana frequently, and genetic differences make some users more liable to progress to dependence. The identification of intermediate phenotypes of cannabis dependence may aid candidate genetic analysis. Promising intermediate phenotypes include craving for marijuana, withdrawal symptoms after abstinence, and sensitivity to its acute effects. A single nucleotide polymorphism (SNP) in the gene encoding for fatty acid amide hydrolase (FAAH) has demonstrated association with substance use disorder diagnoses, but has not been studied with respect to these narrower phenotypes. FAAH is an enzyme that inactivates anandamide, an endogenous agonist for CB(1) receptors (to which Delta(9)-tetrahydrocannabinol binds). CB(1) binding modulates mesocorticolimbic dopamine release, which underlies many facets of addiction.

OBJECTIVES

The SNP, FAAH C385A (rs324420), was examined to determine whether its variance was associated with changes in craving and withdrawal after marijuana abstinence, craving after cue exposure, or sensitivity to the acute effects of marijuana.

MATERIALS AND METHODS

Forty daily marijuana users abstained for 24 h, were presented with a cue-elicited craving paradigm and smoked a marijuana cigarette in the laboratory.

RESULTS

C385A variance was significantly associated with changes in withdrawal after abstinence, and happiness after smoking marijuana in the predicted directions, was associated with changes in heart rate after smoking in the opposite of the predicted direction, and was not associated with changes in craving or other acute effects.

CONCLUSIONS

These data lend support to some previous association studies of C385A, but suggest that further refinement of these intermediate phenotypes is necessary.

Alprazolam and oxazepam block the cue-induced reinstatement of extinguished cocaine seeking in rats

RATIONALE

We have previously reported that pretreatment with benzodiazepines reduces intravenous cocaine self-administration in rats.

OBJECTIVE

This experiment was designed to investigate whether or not benzodiazepines would also inhibit the reinstatement of cocaine seeking induced by the presentation of a conditioned reinforcer.

MATERIALS AND METHODS

Adult male rats were implanted with jugular catheters and trained to self-administer cocaine (0.25 mg/kg/infusion) during daily 2-h sessions. During training, cocaine delivery was paired with the presentation of a tone and the illumination of a houselight. Once a stable baseline of cocaine self-administration was observed, lever pressing was extinguished to less than 20% of baseline rates. During reinstatement testing, responding resulted in the presentation of the conditioned reinforcer (i.e., the houselight and tone previously paired with self-administered cocaine).

RESULTS

The response-contingent presentation of the conditioned reinforcer reliably reinstated cocaine seeking. Pretreatment with alprazolam (2 or 4 mg/kg, ip) or oxazepam (20 or 40 mg/kg, ip) reversed the conditioned reinforcer-induced reinstatement of extinguished cocaine-seeking behavior at doses that did not reliably affect the conditioned reinforcer-induced reinstatement of extinguished food seeking, suggesting that benzodiazepines may not have reduced reinstatement responding due to non-specific reductions in behavior.

CONCLUSIONS

These data suggest that benzodiazepines may be useful in blocking the ability of environmental cues to stimulate cocaine seeking.

Attentional Bias to Drug- and Stress-Related Pictorial Cues in Cocaine Addiction Comorbid with PTSD

Cocaine addiction places a specific burden on mental health services through its comorbidity with other psychiatric disorders. Treatment of patients with cocaine abuse is more complicated when addiction is co-occurring with PTSD. This study used dense-array event-related potential (ERP) technique to investigate whether the patients with this form of dual diagnosis display excessive reactivity to both trauma and drug cues as compared to neutral cues. Cue reactivity refers to a phenomenon in which individuals with a history of drug dependence exhibit verbal, physiological, and behavioral responses to cues associated with their preferred substance of abuse. This study explores ERP differences associated with cue-related responses to both drug and trauma cues in a three-category oddball task using neutral, drug-, and trauma-related pictorial stimuli. The study was conducted on 14 cocaine dependent subjects, 11 subjects with cocaine dependence comorbid with PTSD, and 9 age- and gender-matched control subjects. A 128 channel Electrical Geodesics EEG system was used to record ERP during the visual three-category oddball task with three categories (neutral, drug, stress) of affective pictures. Patients with cocaine dependence and PTSD, as compared to patients with only cocaine addiction and control subjects, showed excessive cue reactivity to both drug- and trauma-related visual stimuli. Most profound differences were found in the amplitude and latency of frontal P3a, and centro-parietal P3b ERP components. Group differences were found as well between patients with cocaine abuse (both addiction-only and dual diagnosis groups) vs. controls on most ERP measures for drug-related cues. We propose that the employed ERP cue reactivity variables could be used as valuable functional outcome measures in dually diagnosed drug addicts undergoing behavioral treatment.

Assessing reactivity to virtual reality alcohol based cues

The use of virtual reality (VR) programs in behavioral science research has been gaining prominence over the past several years. In the field of substance abuse, VR cue reactivity programs have been successfully tested for feasibility in nicotine and cocaine dependent samples. Seeking to expand VR applications in alcohol cue research, a novel VR alcohol cue reactivity assessment system incorporating visual, auditory, and olfactory stimuli was developed and tested. In a controlled trial, 40 non-treatment-seeking drinkers with alcohol use disorders were exposed to VR alcohol cue environments. Subjective craving, attention to alcohol cues, and level of presence (realism of experience) in VR were assessed across the environments. Overall, subjective craving for alcohol increased across the VR alcohol-related cue environments versus VR neutral cue environments. Participants reported high levels of presence in VR, indicating that the environments were perceived as realistic and compelling. These initial findings support the use of VR based cue reactivity environments for use in alcohol cue-based treatment and research.

Cocaine-associated stimuli increase cocaine seeking and activate accumbens core neurons after abstinence

Electrophysiological recordings were completed in rats (n = 14) trained to self-administer cocaine to determine whether activation of nucleus accumbens (Acb) neurons (core vs shell) by cocaine-associated stimuli is enhanced after 1 month of cocaine abstinence. After self-administration training, 170 cells were recorded during a single test session conducted either the next day or 1 month later. The test session consisted of three phases during which (1) the cocaine cue was presented unexpectedly to rats, (2) rats responded for the same cue in the absence of the drug (extinction), and (3) the cocaine cue was presented randomly between cocaine-reinforced responding during resumption of self-administration. The cocaine stimulus significantly increased activation of Acb core (not shell) neurons after 1 month of cocaine abstinence (compared with 1 d); this finding occurred regardless of contingency of cue presentation or cocaine availability. Acb core activation was not observed in other rats (n = 7) presented with the same stimulus never paired with cocaine. The results reflect a cellular neuroadaptation in the Acb core related to cocaine-associated cues that is observed during initial cue exposure and sustained during extinction and resumption of self-administration after prolonged drug abstinence.

A preliminary report on the use of virtual reality technology to elicit craving and cue reactivity in cocaine dependent individuals

In the present feasibility study, we developed a 3-dimensional virtual "crack" cocaine environment and evaluated the environment's ability to elicit subjective craving and cue reactivity (i.e., subjective emotional responding, heart rate and skin conductance) in 11 crack cocaine dependent individuals. Each of the seven 3-D crack cocaine scenes in the cocaine environment depicted actors engaging in a range of using-related behaviors (i.e., smoking crack) whereas the neutral environment contained scenes depicted 3-D aquariums with active aquatic life (baseline measures were obtained following immersion in the neutral environment). Results indicated that craving was significantly elevated during the cocaine-related scenes as compared to baseline. Craving varied by scene content, with scenes depicting active cocaine use eliciting the highest levels of craving. Heart rate was significantly higher in four of the scenes with drug use content and positive affect (i.e., happiness) ratings were significantly lower during cocaine scenes as compared to baseline. Overall, the results suggest that a standardized and stimulus rich virtual reality environment effectively elicits craving and physiologic reactivity. Such technology has potential utility in the development and refinement of exposure-based behavioral and pharmacological interventions for substance use disorders.

A consistent attentional bias for drug-related material in active cocaine users across word and picture versions of the emotional Stroop task

Evidence from a number of drug-abuse populations suggests that an attentional bias for drug-related stimuli can be identified in chronic users. Such an effect has yet to be reliably demonstrated in cocaine users, despite mounting evidence of the salience and reinforcing properties of cocaine-related cues. The aim of the current study was to administer word (modeled on the versions shown to successfully identify attentional biases in alcohol abusers) and picture versions of the emotional Stroop tasks to gauge the reliability of cocaine-specific attentional biases across stimuli domains. A comparison of active cocaine users (n = 23), and their age and education matched controls revealed a significant bias for cocaine-related pictures and words in users. This attentional bias could not be attributed to confounding factors such as slowed response speed of cocaine users, cocaine-related material sharing category ownership, or that the cocaine-related material used in the current study was generally arousing for all participants. A comparison of the different classes of stimuli indicated that cocaine users had a very similar level of difficulty controlling their attention towards both cocaine-related material and incongruent-colour word stimuli, the latter being the traditional measure of attentional control from the Stroop task. These results provide corroborating evidence for cognitive biases being a hallmark of substance dependence.

Utilizing virtual reality to standardize nicotine craving research: a pilot study

Traditional cue reactivity provides a methodology for examining drug triggers and stimuli in laboratory and clinical settings. However, current techniques lack standardization and generalization across research settings. Improved methodologies using virtual reality (VR) cue reactivity extend previous research standardizing exposure to stimuli and exploring reactions to drug cues in a controlled VR setting. In a controlled pilot trial, 13 nicotine-dependent participants were allowed to smoke ad libitum then exposed to VR smoking and VR neutral cues and compared on craving intensity. VR smoking cues significantly increased craving compared to VR neutral cues. On average, craving intensity increased 118% during exposure to VR smoking cues. Implications for substance abuse research and treatment using VR to assess cessation and anticraving medications are discussed.

The impact of stress on addiction

This article will review data obtained from both clinical and preclinical investigations demonstrating that exposure to stress has a significant impact on drug addiction. The preclinical literature suggests that stress increases reward associated with psychomotor stimulants, possibly through a process similar to sensitization. While it is not conclusive that a similar process occurs in humans, a growing clinical literature indicates that there is a link between substance abuse and stress. One explanation for the high concordance between stress-related disorders and drug addiction is the self-medication hypothesis, which suggests that a dually diagnosed person often uses the abused substance to cope with tension associated with life stressors or to relieve symptoms of anxiety and depression resulting from a traumatic event. However, another characteristic of self-administration is that drug delivery and its subsequent effects on the hypothalamo-pituitary-adrenal (HPA) axis are under the direct control of the individual. This controlled activation of the HPA axis may result in the production of an internal state of arousal or stimulation that is actually sought by the individual (i.e., the sensation-seeking hypothesis). During abstinence, exposure to stressors or drug-associated cues can stimulate the HPA axis to remind the individual about the effects of the abused substance, thus producing craving and promoting relapse. Continued investigations into how stress and the subsequent activation of the HPA axis impact addiction will result in the identification of more effective and efficient treatment for substance abuse in humans. Stress reduction, either alone or in combination with pharmacotherapies targeting the HPA axis may prove beneficial in reducing cravings and promoting abstinence in individuals seeking treatment for addiction.

Conditioned stimulus-induced reinstatement of extinguished cocaine seeking in C57BL/6 mice: a mouse model of drug relapse

The scarcity of mouse models for relapse to cocaine seeking has curtailed the study of genetic factors that may contribute to susceptibility for drug relapse. To contribute to the development of a new mouse model of drug relapse, C57BL/6 (B6) mice were trained to press a lever for infusions of cocaine (0.35 mg/kg, i.v.) on a fixed ratio 1 schedule of reinforcement during daily 2-h sessions. A light+tone stimulus complex was presented simultaneously with each cocaine infusion. Mice then underwent a series of extinction sessions during which lever presses had no scheduled consequences. As a result, lever pressing gradually declined. In experiment 1, the ability of the cocaine-paired light+tone stimulus complex to reinstate extinguished cocaine-seeking behavior (i.e. non-reinforced responses) was assessed. In experiment 2, the ability of cocaine priming (0, 1, 2.5, 5, 10, 20, and 40 mg/kg, i.p.) to reinstate cocaine-seeking behavior was measured. B6 mice failed to reinstate in response to i.p. cocaine priming; however, they exhibited robust conditioned stimulus-induced reinstatement. These findings suggest that conditioned stimulus-induced reinstatement in B6 mice is a promising model to study genetic and neurobiological factors that alter the ability of cocaine-paired stimuli to elicit relapse to cocaine seeking behavior.

Influence of cue-conditioning on acquisition, maintenance and relapse of cocaine intravenous self-administration

Conditioning theories propose that, through a Pavlovian associative process, discrete stimuli acquire the ability to elicit neural states involved in the maintenance and relapse of a drug-taking behaviour. Experimental evidence indicates that drug-related cues play a role in relapse, however, their influence on the development and maintenance of drug self-administration has been poorly investigated. In this report, we analysed the effects of a drug-associated cue light on acquisition, maintenance and reinstatement of intravenous cocaine self-administration. The results show that a cocaine-associated cue light can act as an incentive in absence of the drug, but does not directly modify drug-reinforcing effects. Contingent and non-contingent presentations of a cocaine-associated cue light reinstated an extinguished self-administration behaviour. However, regardless of whether or not a cue light was associated with cocaine infusions, rats acquire cocaine intravenous self-administration reaching the same levels of intake. Furthermore, after self-administration has been acquired in presence of the cue light, the omission of the cue light or its non-contingent presentation did not modify rat behaviour. In conclusion, our work shows that cocaine-associated explicit cues do not directly interfere with the reinforcing effects of the drug.

Neural substrates of conditioned-cued relapse to drug-seeking behavior

Relapse to drug use following abstinence is a significant impediment in the long-term treatment of drug abuse and dependence. Conditioned stimuli are believed to be critically involved in activating drug craving and relapse to compulsive drug-taking behavior. Studies in humans and animal models have recently begun to identify the fundamental neural circuitry that mediates relapse following withdrawal from chronic drug self-administration. The current review summarizes key findings in this area that have converged on the amygdalar complex and regions of the frontal lobe as critical structures in conditioned-cued relapse. It is proposed that the amygdala is a key regulator of discrete stimulus-reinforcer associations, while the anterior cingulate and orbitofrontal cortex are critical regulators of relapse evoked by conditioned stimuli that predict drug availability. This corticolimbic circuitry may form the neural basis of multiple long-term conditioned associations produced by a variety of drugs of abuse ranging from psychostimulants to opiates. Future studies aimed at discerning the functional roles of these pathways will provide critical direction for the development of treatments for the prevention of relapse.

Regional brain metabolic activation during craving elicited by recall of previous drug experiences

Cocaine cues elicit craving and physiological responses. The cerebral circuits involved in these are poorly understood. The purpose of this study was to assess the relation between regional brain activation and cocaine cue elicited responses. Thirteen right-handed cocaine abusers were scanned with positron emission tomography (PET) and [F-18] fluorodeoxyglucose (FDG) twice; during an interactive interview about neutral themes and during an interactive interview about cocaine themes designed to elicit cocaine craving. In parallel the behavioral (rated from 0: felt nothing to 10: felt extreme) and cardiovascular responses were recorded. During the cocaine theme interview subjects reported higher self reports for cocaine craving (+2.5+/-3.3, p < or = 0.02) and had higher heart rates (+4.7+/-7.2%, p < or = 0.001), systolic (+4+/-4%, p < or = 0.0001), and diastolic blood pressures (+2.6+/-3.8%, p < or = 0.003) than during the neutral interview. Absolute and relative metabolic values in the orbitofrontal (+16.4+/-17.1%, p < or = 0.005; +11.3+/-14.3%, p < or = 0.008) and left insular cortex (+21.6+/-19.6%, p < or = 0.002; +16.7+/-19.7%, p < or = 0.01) and relative values in cerebellum (+17.9+/-14.8%, p < or = 0.0008) were higher during the cocaine theme than during the neutral theme interview. Relative metabolic values in the right insular region (p < or = 0.0008) were significantly correlated with self reports of cocaine craving. Activation of the temporal insula, a brain region involved with autonomic control, and of the orbitofrontal cortex, a brain region involved with expectancy and reinforcing salience of stimuli, during the cocaine theme support their involvement with craving in cocaine addicted subjects.

Effects of naltrexone on cue-elicited craving for alcohol and cocaine

This study examined the effects of naltrexone (50 mg/day) on mood and self-reported desire for alcohol and cocaine in 26 patients with comorbid alcohol and cocaine abuse/dependence. Two laboratory sessions were conducted, separated by 1 week. During the sessions, subjects viewed 5-min films containing either cocaine, alcohol, or neutral cues. The first session occurred prior to random assignment to medication group and the second session was held after 1 week of double-blind treatment with either naltrexone or placebo. The cocaine-related film induced a greater desire to use cocaine than the desire for alcohol that was induced by the alcohol-related film. This finding was observed using both a simple, one-item analog scale administered during the films and more complex craving questionnaires administered immediately after the films. Collectively, the alcohol and cocaine-related films evoked greater levels of self-reported anxiety and elation, and lower levels of concentration, than the neutral film. Naltrexone did not differ from placebo in reducing the desire to use either cocaine or alcohol.