fMRI BOLD response in high-risk college students (Part 1): during exposure to alcohol, marijuana, polydrug and emotional picture cues

People who binge drink show neuroendocrine tolerance to alcohol cues that is associated with immediate and future drinking- results from a randomized clinical experiment

Neuroendocrine tolerance to alcohol, i.e., a blunted cortisol response to alcohol, has been linked to Ventromedial Prefrontal Cortex (VmPFC) alcohol cue reactivity and relapse risk in severe Alcohol Use Disorders (AUDs), but its role in the development of AUDs is not clear. Recent work suggests that blunted cortisol responses to alcohol cues in individuals who engage in binge drinking (BD) may play a role in motivation to consume larger amounts of alcohol, but the link between this dysregulated endocrine response and BD's neural responses to alcohol cues remains unclear. To examine this, two groups of participants were recruited based on their recent drinking history. Thirty-three BD and 31 non-binging, social drinkers (SD) were exposed to alcohol cues and water cues in two separate 7 T functional magnetic resonance imaging (fMRI) scans. Each scan was followed by the Alcohol Taste Test (ATT) of implicit motivation for alcohol and a post-experiment, one-month prospective measurement of their "real world" drinking behavior. During each scan session, blood plasma was collected repeatedly to examine the separate effects of alcohol cues and alcohol consumption on cortisol levels. Relative to water cues and SD, BD demonstrated blunted cortisol cue reactivity that was negatively associated with VmPFC cue reactivity. In BD, both blunted cortisol and greater VmPFC cue reactivity were related to immediate and future alcohol consumption in the month following the scans. Thus, neuroendocrine tolerance in BD may be associated with increased incentive salience of cues and contribute mechanistically to increased alcohol consumption seen in the development of AUDs.

Updated Perspectives on the Neurobiology of Substance Use Disorders Using Neuroimaging

Substance use problems impair social functioning, academic achievement, and employability. Psychological, biological, social, and environmental factors can contribute to substance use disorders. In recent years, neuroimaging breakthroughs have helped elucidate the mechanisms of substance misuse and its effects on the brain. Functional magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and magnetic resonance spectroscopy (MRS) are all examples. Neuroimaging studies suggest substance misuse affects executive function, reward, memory, and stress systems. Recent neuroimaging research attempts have provided clinicians with improved tools to diagnose patients who misuse substances, comprehend the complicated neuroanatomy and neurobiology involved, and devise individually tailored and monitorable treatment regimens for individuals with substance use disorders. This review describes the most recent developments in drug misuse neuroimaging, including the neurobiology of substance use disorders, neuroimaging, and substance use disorders, established neuroimaging techniques, recent developments with established neuroimaging techniques and substance use disorders, and emerging clinical neuroimaging technology.

Alterations in BNST Intrinsic Functional Connectivity in Early Abstinence from Alcohol Use Disorder

AIMS

Maintaining abstinence from alcohol use disorder (AUD) is extremely challenging, partially due to increased symptoms of anxiety and stress that trigger relapse. Rodent models of AUD have identified that the bed nucleus of the stria terminalis (BNST) contributes to symptoms of anxiety-like behavior and drug-seeking during abstinence. In humans, however, the BNST's role in abstinence remains poorly understood. The aims of this study were to assess BNST network intrinsic functional connectivity in individuals during abstinence from AUD compared to healthy controls and examine associations between BNST intrinsic functional connectivity, anxiety and alcohol use severity during abstinence.

METHODS

The study included resting state fMRI scans from participants aged 21-40 years: 20 participants with AUD in abstinence and 20 healthy controls. Analyses were restricted to five pre-selected brain regions with known BNST structural connections. Linear mixed models were used to test for group differences, with sex as a fixed factor given previously shown sex differences.

RESULTS

BNST-hypothalamus intrinsic connectivity was lower in the abstinent group relative to the control group. There were also pronounced sex differences in both the group and individual analyses; many of the findings were specific to men. Within the abstinent group, anxiety was positively associated with BNST-amygdala and BNST-hypothalamus connectivity, and men, not women, showed a negative relationship between alcohol use severity and BNST-hypothalamus connectivity.

CONCLUSIONS

Understanding differences in connectivity during abstinence may help explain the clinically observed anxiety and depression symptoms during abstinence and may inform the development of individualized treatments.

Are There Neural Overlaps of Reactivity to Illegal Drugs, Tobacco, and Alcohol Cues? With Evidence From ALE and CMA

Abuses of most illegal drugs, including methamphetamine, marijuana, cocaine, heroin, and polydrug, are usually in conjunction with alcohol and tobacco. There are similarities and associations between the behavior, gene, and neurophysiology of such abusers, but the neural overlaps of their cue-reactivity and the correlation of neural overlap with drug craving still needs to be further explored. In this study, an Activation Likelihood Estimation (ALE) was performed on brain activation under legal (tobacco, alcohol) and illegal drug cues, for identifying the similarities in brain functions between different craving states. A Comprehensive meta-analysis (CMA) on the correlation coefficient between brain activation and craving scores in the selected literatures with subjective craving reports explained the degree of the craving via brain imaging results. In ALE, co-activation areas of the three cue-reactivity (posterior cingulate, caudate, and thalamus) suggest that the three cue-reactivity may all arouse drug-use identity which is a predictor of relapse and generation of conditioned reflexes under reward memory, thus leading to illegal drug relapses. In CMA, the brain activation was significantly correlated with subjective craving, with a correlation coefficient of 0.222. The neural overlap of tobacco, alcohol and most of the prevalent illegal drug cues not only further helps us understand the neural mechanism of substance co-abuse and relapse, but also provides implications to detoxification. Furthermore, the correlation between brain activation and craving is low, suggesting the accuracy of craving-based quantitative evaluation by neuroimaging remains unclear.

Alcohol use and interoception - A narrative review

Interoception, defined as the ability to perceive and interpret body signals, may play an important role in alcohol use disorder (AUD). Earlier studies suggested an association between interoception impairment and known risk factors for AUD (e.g., alexithymia, emotion dysregulation, impulsivity, pain). Neurobiological studies show that the neurotoxicity of alcohol affects various elements of the interoceptive system (especially the insula) at structural and functional levels, with differential short/long term impacts. Conversely, primary interoceptive impairments may promote alcohol consumption and foster the evolution towards addiction. Despite convincing evidence demonstrating that interoception impairment may be an important contributor to the development and course of AUD, only a few studies directly evaluated interoceptive abilities in AUD. The research shows that interoceptive accuracy, the objective component of interoception, is lower in AUD individuals, and is correlated with craving and emotion dysregulation. Interoceptive sensibility is in turn higher in AUD individuals compared to healthy controls. Moreover, there is evidence that therapy focused on improving the ability to sense signals from the body in addiction treatment is effective. However, important methodological limitations in interoceptive measures persist, and it is therefore necessary to further investigate the associations between interoception and AUD.

Neural activation to loss and reward among alcohol naive adolescents who later initiate alcohol use

Adolescent alcohol use is associated with adverse psychosocial outcomes, including an increased risk of alcohol use disorder in adulthood. It is therefore important to identify risk factors of alcohol initiation in adolescence. Research to date has shown that altered neural activation to reward is associated with alcohol use in adolescence; however, few studies have focused on neural activation to loss and alcohol use. The current study examined neural activation to loss and reward among 64 alcohol naive 12−14 year olds that did (n = 20) and did not initiate alcohol use by a three year follow-up period. Results showed that compared to adolescents that did not initiate alcohol use, adolescents that did initiate alcohol use by the three year follow-up period had increased activation to loss in the left striatum (i.e., putamen), right precuneus, and the brainstem/pons when they were alcohol naive at baseline. By contrast, alcohol initiation was not associated with neural activation to winning a reward. These results suggest that increased activation in brain regions implicated in salience, error detection/self-referential processing, and sensorimotor function, especially to negative outcomes, may represent an initial vulnerability factor for alcohol use in adolescence.

BNST-insula structural connectivity in humans

The bed nucleus of the stria terminalis (BNST) is emerging as a critical region in multiple psychiatric disorders including anxiety, PTSD, and alcohol and substance use disorders. In conjunction with growing knowledge of the BNST, an increasing number of studies examine connections of the BNST and how those connections impact BNST function. The importance of this BNST network is highlighted by rodent studies demonstrating that projections from other brain regions regulate BNST activity and influence BNST-related behavior. While many animal and human studies replicate the components of the BNST network, to date, structural connections between the BNST and insula have only been described in rodents and have yet to be shown in humans. In this study, we used probabilistic tractography to examine BNST-insula structural connectivity in humans. We used two methods of dividing the insula: 1) anterior and posterior insula, to be consistent with much of the existing insula literature; and 2) eight subregions that represent informative cytoarchitectural divisions. We found evidence of a BNST-insula structural connection in humans, with the strongest BNST connectivity localized to the anteroventral insula, a region of agranular cortex. BNST-insula connectivity differed by hemisphere and was moderated by sex. These results translate rodent findings to humans and lay an important foundation for future studies examining the role of BNST-insula pathways in psychiatric disorders.

Disrupted resting-state brain functional network in methamphetamine abusers: A brain source space study by EEG

This study aimed to examine the effects of chronic methamphetamine use on the topological organization of whole-brain functional connectivity network (FCN) by reconstruction of neural-activity time series at resting-state. The EEG of 36 individuals with methamphetamine use disorder (IWMUD) and 24 normal controls (NCs) were recorded, pre-processed and source-reconstructed using standardized low-resolution tomography (sLORETA). The brain FCNs of participants were constructed and between-group differences in network topological properties were investigated using graph theoretical analysis. IWMUD showed decreased characteristic path length, increased clustering coefficient and small-world index at delta and gamma frequency bands compared to NCs. Moreover, abnormal changes in inter-regional connectivity and network hubs were observed in all the frequency bands. The results suggest that the IWMUD and NCs have distinct FCNs at all the frequency bands, particularly at the delta and gamma bands, in which deviated small-world brain topology was found in IWMUD.

Resonance-Paced Breathing Alters Neural Response to Visual Cues: Proof-of-Concept for a Neuroscience-Informed Adjunct to Addiction Treatments

Conscious attempts to regulate alcohol and drug use are often undermined by automatic attention and arousal processes that are activated in the context of salient cues. Response to these cues involves body and brain signals that are linked via dynamic feedback loops, yet no studies have targeted the cardiovascular system as a potential conduit to alter automatic neural processes that maintain cue salience. This proof-of-concept study examined within-person changes in neural response to parallel but unique sets of visual alcohol-related cues at two points in time: prior to versus following a brief behavioral intervention. The active intervention was resonance breathing, a rhythmical breathing task paced at 0.1 Hz (6 breaths per minute) that helps normalize neurocardiac feedback. The control intervention was a low-demand cognitive task. Functional magnetic resonance imaging (fMRI) was used to assess changes in brain response to the cues presented before (A1) and after (A2) the intervention in 41 emerging adult men and women with varying drinking behaviors. The resonance breathing group exhibited significantly less activation to A2 cues compared with A1 cues in left inferior and superior lateral occipital cortices, right inferior lateral occipital cortex, bilateral occipital pole, and temporal occipital fusiform cortices. This group also showed significantly greater activation to A2 cues compared with A1 cues in medial prefrontal, anterior and posterior cingulate, and precuneus cortices, paracingulate, and lingual gyri. The control group showed no significant changes. Thus, following resonance breathing, activation in brain regions involved in visual processing of cues was reduced, while activation in brain areas implicated in behavioral control, internally directed cognition, and brain-body integration was increased. These findings provide preliminary evidence that manipulation of the cardiovascular system with resonance breathing alters neural activation in a manner theoretically consistent with a dampening of automatic sensory input and strengthening of higher-level cognitive processing.

The neural correlates of the unified percept of alcohol-related craving: a fMRI and EEG study

Alcohol addiction is accompanied by aberrant neural activity. Previously, task-based fMRI and resting-state EEG studies have revealed that craving, a critical component of addiction, is linked to abnormal activity in cortical regions including the dorsal anterior cingulate cortex (dACC), nucleus accumbens (NAcc), posterior cingulate cortex (PCC) and pregenual anterior cingulate cortex (pgACC), etc. In this study, we combine these two imaging techniques to investigate a group of alcohol-addicted patients and provide convergent evidence for the neural correlates of craving not only in alcohol but substance abuse in general. We observe abnormal BOLD signal levels in the dACC, NAcc, pgACC, PCC, amygdala, and parahippocampus (PHC) in a cue-reactivity fMRI experiment. These findings are consistent with increased beta-band activity in the dACC and pgACC in resting-state EEG. We further observe desynchronization characterized by decreased functional connectivity in cue-based fMRI and hypersynchronization characterized by increased functional connectivity between these regions in the theta frequency band. The results of our study show a consistent pattern of alcohol craving elicited by external cues and internal desires. Given the advantage of superior spatial and temporal resolution, we hypothesize a "central craving network" that integrates the different aspects of alcohol addiction into a unified percept.

Association between pubertal stage at first drink and neural reward processing in early adulthood

Puberty is a critical time period during human development. It is characterized by high levels of risk-taking behavior, such as increased alcohol consumption, and is accompanied by various neurobiological changes. Recent studies in animals and humans have revealed that the pubertal stage at first drink (PSFD) significantly impacts drinking behavior in adulthood. Moreover, neuronal alterations of the dopaminergic reward system have been associated with alcohol abuse or addiction. This study aimed to clarify the impact of PSFD on neuronal characteristics of reward processing linked to alcohol-related problems. One hundred sixty-eight healthy young adults from a prospective study covering 25 years participated in a monetary incentive delay task measured with simultaneous EEG-fMRI. PSFD was determined according to the age at menarche or Tanner stage of pubertal development, respectively. Alcohol-related problems in early adulthood were assessed with the Alcohol Use Disorder Identification Test (AUDIT). During reward anticipation, decreased fMRI activation of the frontal cortex and increased preparatory EEG activity (contingent negative variation) occurred with pubertal compared to postpubertal first alcohol intake. Moreover, alcohol-related problems during early adulthood were increased in pubertal compared to postpubertal beginners, which was mediated by neuronal activation of the right medial frontal gyrus. At reward delivery, increased fMRI activation of the left caudate and higher feedback-related EEG negativity were detected in pubertal compared to postpubertal beginners. Together with animal findings, these results implicate PSFD as a potential modulator of psychopathology, involving altered reward anticipation. Both PSFD timing and reward processing might thus be potential targets for early prevention and intervention.

Modulation of sensitivity to alcohol by cortical and thalamic brain regions

The nucleus accumbens core (AcbC) is a key brain region known to regulate the discriminative stimulus/interoceptive effects of alcohol. As such, the goal of the present work was to identify AcbC projection regions that may also modulate sensitivity to alcohol. Accordingly, AcbC afferent projections were identified in behaviorally naïve rats using a retrograde tracer which led to the focus on the medial prefrontal cortex (mPFC), insular cortex (IC) and rhomboid thalamic nucleus (Rh). Next, to examine the possible role of these brain regions in modulating sensitivity to alcohol, neuronal response to alcohol in rats trained to discriminate alcohol (1 g/kg, intragastric [IG]) vs. water was examined using a two-lever drug discrimination task. As such, rats were administered water or alcohol (1 g/kg, IG) and brain tissue was processed for c-Fos immunoreactivity (IR), a marker of neuronal activity. Alcohol decreased c-Fos IR in the mPFC, IC, Rh and AcbC. Lastly, site-specific pharmacological inactivation with muscimol + baclofen (GABA_A agonist + GABA_B agonist) was used to determine the functional role of the mPFC, IC and Rh in modulating the interoceptive effects of alcohol in rats trained to discriminate alcohol (1 g/kg, IG) vs. water. mPFC inactivation resulted in full substitution for the alcohol training dose, and IC and Rh inactivation produced partial alcohol-like effects, demonstrating the importance of these regions, with known projections to the AcbC, in modulating sensitivity to alcohol. Together, these data demonstrate a site of action of alcohol and the recruitment of cortical/thalamic regions in modulating sensitivity to the interoceptive effects of alcohol.

Craving versus control: Negative urgency and neural correlates of alcohol cue reactivity

BACKGROUND

Alcohol abuse is a common and costly practice. Individuals high in negative urgency, the tendency to act rashly when experiencing negative emotions, are at particular risk for abusing alcohol. Alcohol abuse among individuals high in negative urgency may be due to (a) increased activity in the brain's striatum, (b) decreased activity in brain regions associated with self-control, or (c) a combination of the two.

METHODS

Thirty eight non-alcohol-dependent participants completed a measure of negative urgency and then underwent functional magnetic resonance imaging (fMRI) while passively viewing pleasant and alcohol images.

RESULTS

Alcohol images (as compared to pleasant images) were associated with activation in the caudate nucleus, a brain region associated with linking reward to external stimuli. Negative urgency (above and beyond other facets of impulsivity) correlated positively with this caudate activation in response to alcohol images. Alcohol images and negative urgency were unassociated with activity in the lateral prefrontal cortex, a self-regulatory brain region.

CONCLUSIONS

These findings provide initial support that the alcohol abuse observed among individuals high in negative urgency may be due, in part, to heightened reactivity in the striatum to alcohol. Investigating such neural contributors to self-regulation failure is crucial to reducing substance abuse.

Prefrontal recruitment during social rejection predicts greater subsequent self-regulatory imbalance and impairment: neural and longitudinal evidence

Social rejection impairs self-regulation, yet the neural mechanisms underlying this relationship remain unknown. The right ventrolateral prefrontal cortex (rVLPFC) facilitates self-regulation and plays a robust role in regulating the distress of social rejection. However, recruiting this region's inhibitory function during social rejection may come at a self-regulatory cost. As supported by prominent theories of self-regulation, we hypothesized that greater rVLPFC recruitment during rejection would predict a subsequent self-regulatory imbalance that favored reflexive impulses (i.e., cravings), which would then impair self-regulation. Supporting our hypotheses, rVLPFC activation during social rejection was associated with greater subsequent nucleus accumbens (NAcc) activation and lesser functional connectivity between the NAcc and rVLPFC to appetitive cues. Over seven days, the effect of daily felt rejection on daily self-regulatory impairment was exacerbated among participants who showed a stronger rVLPFC response to social rejection. This interactive effect was mirrored in the effect of daily felt rejection on heightened daily alcohol cravings. Our findings suggest that social rejection likely impairs self-regulation by recruiting the rVLPFC, which then tips the regulatory balance towards reward-based impulses.

Medial parietal cortex activation related to attention control involving alcohol cues

Automatic attentional engagement toward and disengagement from alcohol cues play a role in alcohol use and dependence. In the current study, social drinkers performed a spatial cueing task designed to evoke conflict between such automatic processes and task instructions, a potentially important task feature from the perspective of recent dual-process models of addiction. Subjects received instructions either to direct their attention toward pictures of alcoholic beverages, and away from non-alcohol beverages; or to direct their attention toward pictures of non-alcoholic beverages, and away from alcohol beverages. Instructions were varied per block. Activation in medial parietal cortex was found during "approach alcohol" versus "avoid-alcohol" blocks. This region is associated with the, possibly automatic, shifting of attention between stimulus features. Subjects thus appeared to shift attention away from certain features of alcoholic cues when attention had to be directed toward their location. Further, activation in voxels located close to this region was negatively correlated with riskier drinking behavior. A tentative interpretation of the results is that risky drinking may be associated with a reduced automatic tendency to shift attention away from potentially distracting task-irrelevant alcohol cues. Future study is needed to test this interpretation, and to further determine the role of medial posterior regions in automatic alcohol-related attentional processes in general.

Changes in alcohol-related brain networks across the first year of college: a prospective pilot study using fMRI effective connectivity mapping

The upsurge in alcohol use that often occurs during the first year of college has been convincingly linked to a number of negative psychosocial consequences and may negatively affect brain development. In this longitudinal functional magnetic resonance imaging (fMRI) pilot study, we examined changes in neural responses to alcohol cues across the first year of college in a normative sample of late adolescents. Participants (N=11) were scanned three times across their first year of college (summer, first semester, second semester), while completing a go/no-go task in which images of alcoholic and non-alcoholic beverages were the response cues. A state-of-the-art effective connectivity mapping technique was used to capture spatiotemporal relations among brain regions of interest (ROIs) at the level of the group and the individual. Effective connections among ROIs implicated in cognitive control were greatest at the second assessment (when negative consequences of alcohol use increased), and effective connections among ROIs implicated in emotion processing were lower (and response times were slower) when participants were instructed to respond to alcohol cues compared to non-alcohol cues. These preliminary findings demonstrate the value of a prospective effective connectivity approach for understanding adolescent changes in alcohol-related neural processes.

High and low sensation seeking adolescents show distinct patterns of brain activity during reward processing

Previous research has shown that personality characteristics, such as sensation seeking (SS), are strong predictors of risk-taking behavior during adolescence. However, the relationship between levels of SS and brain response has not been studied during this time period. Given the prevalence of risky behavior during adolescence, it is important to understand neurobiological differences in reward sensitivity between youth with high and low SS personalities. To this end, we used functional magnetic resonance imaging (fMRI) to examine differences in brain activity in an adolescent sample that included 27 high (HSS) and 27 low sensation seekers (LSS), defined by the Impulsive Sensation Seeking scale of the Zuckerman-Kuhlman Personality Questionnaire (Zuckerman et al., 1993). In the scanner, participants played a modified Wheel of Fortune decision-making task (Cservenka and Nagel, 2012) that resulted in trials with monetary Wins or No Wins. We compared age- and sex-matched adolescent HSS and LSS (mean age=13.94±1.05) on brain activity by contrasting Win vs. No Win trials. Our findings indicate that HSS show greater bilateral insular and prefrontal cortex (PFC) brain response on Win vs. No Win compared to LSS. Analysis of simple effects showed that while LSS showed comparable brain activity in these areas during Wins and No Wins, HSS showed significant differences in brain response to winning (activation) vs. not winning (deactivation), with between-group comparison suggesting significant differences in brain response, largely to reward absence. Group differences in insular activation between reward receipt and absence may suggest weak autonomic arousal to negative outcomes in HSS compared with LSS. Additionally, since the PFC is important for goal-directed behavior and attention, the current results may reflect that HSS allocate fewer attentional resources to negative outcomes than LSS. This insensitivity to reward absence in HSS may lead to a greater likelihood of maladaptive choices when negative consequences are not considered, and may be an early neural marker of decreased loss sensitivity that has been seen in addiction. This neurobiological information may ultimately be helpful in establishing prevention strategies aimed at reducing youth risk-taking and suggests value in further examination of neural associations with personality characteristics during adolescence.

Influence of alcohol use and family history of alcoholism on neural response to alcohol cues in college drinkers

BACKGROUND

Heavy drinkers show altered functional magnetic resonance imaging (fMRI) response to alcohol cues. Little is known about alcohol cue reactivity among college age drinkers, who show the greatest rates of alcohol use disorders. Family history of alcoholism (family history positive [FHP]) is a risk factor for problematic drinking, but the impact on alcohol cue reactivity is unclear. We investigated the influence of heavy drinking and family history of alcoholism on alcohol cue-related fMRI response among college students.

METHODS

Participants were 19 family history negative (FHN) light drinkers, 11 FHP light drinkers, 25 FHN heavy drinkers, and 10 FHP heavy drinkers, aged 18 to 21. During fMRI scanning, participants viewed alcohol images, nonalcohol beverage images, and degraded control images, with each beverage image presented twice. We characterized blood oxygen level-dependent (BOLD) contrast for alcohol versus nonalcohol images and examined BOLD response to repeated alcohol images to understand exposure effects.

RESULTS

Heavy drinkers exhibited greater BOLD response than light drinkers in posterior visual association regions, anterior cingulate, medial frontal cortex, hippocampus, amygdala, and dorsal striatum, and hyperactivation to repeated alcohol images in temporo-parietal, frontal, and insular regions (clusters > 8,127 μl, p < 0.05). FHP individuals showed increased activation to repeated alcohol images in temporo-parietal regions, fusiform, and hippocampus. There were no interactions between family history and drinking group.

CONCLUSIONS

Our results parallel findings of hyperactivation to alcohol cues among heavy drinkers in regions subserving visual attention, memory, motivation, and habit. Heavy drinkers demonstrated heightened activation to repeated alcohol images, which could influence continued drinking. Family history of alcoholism was associated with greater response to repeated alcohol images in regions underlying visual attention, recognition, and encoding, which could suggest aspects of alcohol cue reactivity that are independent of personal drinking. Heavy drinking and family history of alcoholism may have differential impacts on neural circuitry involved in cue reactivity.

Altered prefrontal and insular cortical thickness in adolescent marijuana users

INTRODUCTION

There are limited data regarding the impact of marijuana (MJ) on cortical development during adolescence. Adolescence is a period of substantial brain maturation and cortical thickness abnormalities may be indicative of disruptions of normal cortical development. This investigation applied cortical-surface based techniques to compare cortical thickness measures in MJ using adolescents compared to non-using controls.

METHODS

Eighteen adolescents with heavy MJ use and 18 non-using controls similar in age received MRI scans using a 3T Siemens scanner. Cortical reconstruction and volumetric segmentation was performed with FreeSurfer. Group differences in cortical thickness were assessed using statistical difference maps covarying for age and gender.

RESULTS

Compared to non-users, MJ users had decreased cortical thickness in right caudal middle frontal, bilateral insula and bilateral superior frontal cortices. Marijuana users had increased cortical thickness in the bilateral lingual, right superior temporal, right inferior parietal and left paracentral regions. In the MJ users, negative correlations were found between frontal and lingual regions for urinary cannabinoid levels and between age of onset of use and the right superior frontal gyrus.

CONCLUSION

This is one of the first studies to evaluate cortical thickness in a group of adolescents with heavy MJ use compared to non-users. Our findings are consistent with prior studies that documented abnormalities in prefrontal and insular regions. Our results suggest that age of regular use may be associated with altered prefrontal cortical gray matter development in adolescents. Furthermore, reduced insular cortical thickness may be a biological marker for increased risk of substance dependence.

fMRI BOLD response of high-risk college students (Part 2): during memory priming of alcohol, marijuana and polydrug picture cues

AIMS

This study examined brain activity using functional magnetic resonance imaging (fMRI) and reaction time (RT) during an implicit repetition priming memory task involving alcohol, polydrug, marijuana and emotional picture cues.

METHODS

Participants were 5 male and 5 female high-risk college students who had just participated in a cue exposure study (Ray et al., this issue). fMRI and RT data were collected while participants made decisions about previously seen and new picture cues.

RESULTS

Both behavioral RT and brain imaging data revealed strong memory priming for drug and alcohol cues. Neurologically, a repetition priming effect (suppression in neural activity for repeated cues) was observed in response to alcohol cues in the left prefrontal, bilateral occipital, and bilateral occipitotemporal regions, as well as right insula and right precuneus (Z ranged from 3.03 to 3.31 P < 0.05). Polydrug cues elicited priming in the occipital and temporal areas, and marijuana cues in the occipital area.

CONCLUSIONS

Prefrontal and insular cortex involvement both in reactivity to alcohol cues (Ray et al., this issue) and subsequent implicit memory processing of these cues, as found in this study, suggests their potential role in the maintenance of high-risk alcohol use behaviors.