Alcohol dependence has repeatedly been associated with impulsive choice, or the inability to choose large delayed rewards over smaller, but more immediate rewards. However, the neural basis of impulsive choice in alcohol use disorders is not well understood.
One hundred fifty one individuals with a range of alcohol use from social drinking to severe alcohol dependence completed a delay discounting task while undergoing functional magnetic resonance imaging (fMRI). Participants received customized trials designed to ensure an approximately equivalent number of immediate responses.
Delaying gratification recruited regions involved in cognitive control, conflict monitoring, and the interpretation of somatic states. Individuals with more severe alcohol use problems showed increased discounting of delayed rewards and greater activation in several regions including supplementary motor area, insula/orbitofrontal cortex, inferior frontal gyrus, and the precuneus.
These results suggest that impulsive choice in alcohol dependence is the result of functional anomolies in widely distributed, but interconnected brain regions involved in cognitive and emotional control. Further, our results suggest that the neural mechanisms of impulsive choice in alcohol use disorders both overlaps with that observed in previous studies, and shows that individuals with alcohol use disorders recruit additional mechanisms when making intertemporal choices.
Delay discounting; intertemporal choice; impulsivity; delayed gratification
Evidence for shared heritable influences across domains of substance use suggests that some genetic variants influence broad risk for externalizing behaviors. Theories of externalizing psychopathology also suggest that genetic liability for substance use manifests as temperamental risk factors, particularly those related to behavioral disinhibition, during adolescence. The cholinergic muscarinic receptor 2 gene (CHRM2) is a promising candidate for studying genetic influences on broad-based risk for externalizing traits. This study examined a candidate CHRM2 polymorphism (rs1455858) in relation to substance use and personality measures of disinhibition in a sample of high-risk adolescents (n = 124). Bivariate analyses and structural equation modeling (SEM) evaluated associations of rs1455858 with measures of drug involvement (alcohol, tobacco and marijuana) and disinhibition (indexed by impulsivity and sensation seeking scores). Bivariate analyses showed significant associations of CHRM2 with several behavioral phenotypes. In SEM analyses CHRM2 related significantly to latent measures of substance use and disinhibition; additionally, disinhibition mediated the association of CHRM2 with substance use. These results suggest that CHRM2 variants are potentially relevant for adolescent substance use and that temperamental risk factors could contribute to these associations.
Disinhibitory psychopathology; drug dependence; response inhibition; risk-taking; SNP
Enhanced motivational salience towards smoking cues is a consequence of chronic nicotine use, but the degree to which this value increases beyond that of other appetitive cues is unknown. In addition, it is unclear how connectivity between brain regions influences cue reactivity and how cue reactivity and functional connectivity are related to nicotine dependence severity. This study examined neural responses during the presentation of smoking cues and appetitive control cues, as well as functional connectivity in 116 smokers with a range of nicotine dependence severity. Smoking cues elicited greater response above baseline than food cues in orbitofrontal cortex (OFC) and supplementary motor area (SMA) and less deactivation below baseline in middle frontal gyrus, inferior parietal lobe, and middle temporal gyrus. Psychophysiological interaction (PPI) analysis using right OFC as a seed revealed increased connectivity with somatosensory cortex and lateral inferior parietal lobe during smoking cues compared with food cues. Similarly, a PPI analysis using left insula as a seed showed stronger connectivity with somatosensory cortex, right insula, OFC, and striatum. Finally, relationships with nicotine dependence scores showed enhanced response in insula and dorsal anterior cingulate cortex in the smoking vs food comparison, and increased connectivity between insula and circuits involved in motivated behavior. Combined, these results suggest that smokers engage attentional networks and default mode networks involved in self-referential processing to a greater degree during smoking cues. In addition, individuals with greater nicotine dependence severity show increased engagement of sensorimotor and motor preparation circuits, suggesting increased reliance on habitual behavior.
abuse; biological psychiatry; craving; functional connectivity; imaging; clinical or preclinical; insula; nicotine dependence; psychiatry & behavioral sciences; craving; insula; functional connectivity; nicotine dependence
Juvenile justice involved youth are at great risk for negative outcomes of risky sexual behavior including HIV/AIDS. Given the strong connection between alcohol use and risky sex in this population, it is important to consider alcohol use in interventions designed to decrease risky sexual behavior. This paper provides support for an integrative translational model that incorporates psychosocial, neurobiological, and genetic factors to better predict alcohol-related sexual risk behavior. Specifically, we present the design, methods, and baseline data from a complex randomized control trial, Project SHARP (Sexual Health and Adolescent Risk Prevention) in order to illustrate how this broad array of factors can best predict alcohol-related sexual risk behavior. Participants were justice-involved adolescents (n=284) who completed an fMRI and self-report assessments prior to randomization to either a sexual risk plus alcohol risk reduction group intervention or to an information-only contact control group intervention. Structural equation modeling was utilized and findings supported the hypothesized relationships in the translational model. Preliminary data suggest that interventions among justice-involved adolescents targeting alcohol-related sexual risk behavior may be more effective if a biopsychosocial approach is considered.
Neurocognition; Genetics; Justice-involved adolescents; Risky sex; Alcohol; Condom
Neuroimaging studies have shown that white matter damage accompanies excessive alcohol use, but the functional correlates of alcohol-related white matter disruption remain unknown. This study applied tract-based spatial statistics (TBSS) to diffusion tensor imaging (DTI) data from 332 heavy drinkers (mean age = 31.2 ± 9.4; 31% female) to obtain averaged fractional anisotropy (FA) values of 18 white matter tracts. Statistical analyses examined correlations of FA values with blood-oxygenation-level-dependent (BOLD) response to an alcohol taste cue, measured with functional magnetic resonance imaging (fMRI). FA values of nine white matter tracts (anterior corona radiata, body of corpus callosum, cingulate gyrus, external capsule, fornix, inferior frontooccipital fasciculus, posterior corona radiata, retrolenticular limb of internal capsule, and superior longitudinal fasciculus) were significantly, negatively correlated with BOLD activation in medial frontal gyrus, parahippocampal gyrus, fusiform gyrus, cingulum, thalamus, caudate, putamen, insula, and cerebellum. The inverse relation between white matter integrity and functional activation during the alcohol taste cue provides support for the hypothesis that lower white matter integrity in frontoparietal and corticolimbic networks is a factor in loss of control over alcohol consumption.
Alcohol use disorders; diffusion tensor imaging; functional magnetic resonance imaging; tract-based spatial statistics; white matter
Negative reinforcement results in behavior to escape or avoid an aversive outcome. Withdrawal symptoms are purported to be negative reinforcers in perpetuating substance dependence, but little is known about negative reinforcement learning in this population. The purpose of this study was to examine reinforcement learning in substance dependent individuals (SDI), with an emphasis on assessing negative reinforcement learning. We modified the Iowa Gambling Task to separately assess positive and negative reinforcement. We hypothesized that SDI would show differences in negative reinforcement learning compared to controls and we investigated whether learning differed as a function of the relative magnitude or frequency of the reinforcer.
Thirty subjects dependent on psychostimulants were compared with 28 community controls on a decision making task that manipulated outcome frequencies and magnitudes and required an action to avoid a negative outcome.
SDI did not learn to avoid negative outcomes to the same degree as controls. This difference was driven by the magnitude, not the frequency, of negative feedback. In contrast, approach behaviors in response to positive reinforcement were similar in both groups.
Our findings are consistent with a specific deficit in negative reinforcement learning in SDI. SDI were relatively insensitive to the magnitude, not frequency, of loss. If this generalizes to drug-related stimuli, it suggests that repeated episodes of withdrawal may drive relapse more than the severity of a single episode.
Substance dependence; decision making; negative reinforcement
Copy number variations (CNV) can alter the DNA sequence in blocks ranging from kilobases to megabases, involving more total nucleotides than single nucleotide polymorphisms. Yet, its impact in humans is far from fully understood. In this study, we investigate the relationship of genome wide CNVs with brain function elicited by an alcohol cue in 300 participants with alcohol use disorders. First, we extracted refined neurobiological phenotypes, the brain responses to an alcohol cue versus a juice cue in the precuneus, thalamus, and anterior cingulate cortex (ACC). Then, we correlated the CNVs with incidence frequency >1% to the neurobiological phenotypes. One CNV region at 22q13.1 was identified to be associated with alcohol dependence severity and the brain response to alcohol cues. Specifically, the 22k base-pair homozygous deletion at 22q13.1 affects genes APOBEC3a and APOBEC3b. Carriers of this homozygous deletion show a significantly higher score in the alcohol dependence severity (p < 0.05) and increased response to alcohol cues in the precuneus (p < 10-12) than other participants. Tests of a mediation model indicate that the precuneus mediates the association between the homozygous deletions and alcohol dependence severity. Interestingly, the precuneus is not only anatomically and functionally connected to the ACC and thalamus (the main active regions to the alcohol cue), but also has the most predictive power to the alcohol dependence severity. These findings suggest that the homozygous deletion at 22q13.1 may have an important impact on the function of the precuneus with downstream implications for alcohol dependence.
Alcohol use disorders; copy number variation; homozygous deletion; neurobiological phenotype; 22q13.1; precuneus; alcohol dependence
Although numerous studies provide general support for the importance of genetic factors in the risk for alcohol use disorders (AUDs), candidate gene and genome-wide studies have yet to identify a set of genetic variations that explain a significant portion of the variance in AUDs. One reason is that alcohol-related phenotypes used in genetic studies are typically based on highly heterogeneous diagnostic categories. Therefore, identifying neurobiological phenotypes related to neuroadaptations that drive the development of AUDs is critical for the future success of genetic and epigenetic studies. One such neurobiological phenotype is the degree to which exposure to alcohol taste cues recruits the basal ganglia, prefrontal cortex, and motor areas, all of which have been shown to have a critical role in addictive behaviors in animal studies. To that end, this study was designed to examine whether cue-elicited responses of these structures are associated with AUD severity in a large sample (n=326) using voxelwise and functional connectivity measures. Results suggested that alcohol cues significantly activated dorsal striatum, insula/orbitofrontal cortex, anterior cingulate cortex, and ventral tegmental area. AUD severity was moderately correlated with regions involved in incentive salience such as the nucleus accumbens and amygdala, and stronger relationships with precuneus, insula, and dorsal striatum. The findings indicate that AUDs are related to neuroadaptations in these regions and that these measures may represent important neurobiological phenotypes for subsequent genetic studies.
craving; alcohol use disorder; phenotype; striatum; anterior cingulate cortex; alcohol & alcoholism; addiction & substance abuse; imaging; clinical or preclinical; biological psychiatry; craving; alcohol use disorder; phenotype; insula; anterior cingulate cortex
The inhibition of unwanted behaviors is considered an effortful and controlled ability. However, inhibition also requires the detection of contexts indicating that old behaviors may be inappropriate – in other words, inhibition requires the ability to monitor context in the service of goals, which we refer to as context-monitoring. Using behavioral, neuroimaging, electrophysiological and computational approaches, we tested whether motoric stopping per se is the cognitively-controlled process supporting response inhibition, or whether context-monitoring may fill this role. Our results demonstrate that inhibition does not require control mechanisms beyond those involved in context-monitoring, and that such control mechanisms are the same regardless of stopping demands. These results challenge dominant accounts of inhibitory control, which posit that motoric stopping is the cognitively-controlled process of response inhibition, and clarify emerging debates on the frontal substrates of response inhibition by replacing the centrality of controlled mechanisms for motoric stopping with context-monitoring.
Adolescence is commonly characterized by impulsivity, poor decision-making, and lack of foresight. However, the developmental neural underpinnings of these characteristics are not well established.
To test the hypothesis that these adolescent behaviors are linked to under-developed proactive control mechanisms, the present study employed a hybrid block/event-related functional Magnetic Resonance Imaging (fMRI) Stroop paradigm combined with self-report questionnaires in a large sample of adolescents and adults, ranging in age from 14 to 25. Compared to adults, adolescents under-activated a set of brain regions implicated in proactive top-down control across task blocks comprised of difficult and easy trials. Moreover, the magnitude of lateral prefrontal activity in adolescents predicted self-report measures of impulse control, foresight, and resistance to peer pressure. Consistent with reactive compensatory mechanisms to reduced proactive control, older adolescents exhibited elevated transient activity in regions implicated in response-related interference resolution.
Collectively, these results suggest that maturation of cognitive control may be partly mediated by earlier development of neural systems supporting reactive control and delayed development of systems supporting proactive control. Importantly, the development of these mechanisms is associated with cognitive control in real-life behaviors.
Studies suggest that polymorphisms in the D4 dopamine receptor (DRD4) and opioid receptor, μ1 (OPRM1) genes are involved in differential response to the effects of alcohol and to alcohol cues. However, to date, the mechanisms that underlie these differences remain largely unknown.
Using functional magnetic resonance imaging, hemodynamic response in mesocorticolimbic structures after exposure to alcohol tastes was contrasted with a control taste and compared between DRD4 variable number of tandem repeats (VNTR) genotypes and OPRM1 A118G genotypes. Additionally, the effects of a priming dose of alcohol on this response were examined.
The results indicated that DRD4 VNTR >7 repeat individuals (DRD4.L) had significantly greater response to alcohol cues in the orbitofrontal cortex, anterior cingulate gyrus, and striatum compared with individuals with <7 repeats (DRD4.S) prior to a priming dose of alcohol (p < 0.05), but not after a priming dose. In the OPRM1 comparisons, results showed that individuals with at least 1 copy of the OPRM1 + 118 G allele had greater hemodynamic response in mesocorticolimbic areas both before and after priming compared with those who were homozygous for the OPRM1 + 118 A allele. For the DRD4.L and OPRM1 + 118 G groups, brain response in the striatum was highly correlated with measures of alcohol use and behavior such that greater activity corresponded with greater frequency and quantity of alcohol use.
The DRD4 VNTR and OPRM1 A118G polymorphisms are associated with functional neural changes in mesocorticolimbic structures after exposure to alcohol cues. This provides evidence for the contributions of the DRD4 and OPRM1 genes in modulating neural activity in structures that are involved in the motivation to drink.
DRD4; OPRM1; Alcohol; Craving; fMRI; Mesocorticolimbic
Although many neuroimaging studies have examined changes in brain function in adults with substance use disorders, far fewer have examined adolescents. This study investigated patterns of brain activation in adolescents with severe substance and conduct problems (SCP) compared to controls.
Functional magnetic resonance imaging (fMRI) at 1.5 Tesla assessed brain activation in 12 adolescent males with SCP, ranging in age from 14 to 18, and 12 controls similar in age, gender, and neighborhood while performing the attentionally-demanding Stroop task.
Even though the adolescents with SCP performed as well as the controls, they activated a more extensive set of brain structures for incongruent (e.g., “red” in blue ink) versus congruent (e.g. “red” in red ink) trials. These regions included parahippocampal regions bilaterally, posterior regions involved in language-related processing, right-sided medial prefrontal areas, and subcortical regions including the the thalamus and caudate.
These preliminary results suggest that the neural mechanisms of attentional control in youth with SCP differ from youth without such problems. This difficulty may prevent SCP youth from ignoring salient but distracting information in the environment, such as drug-related information.