Search tips
Search criteria

Results 1-6 (6)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Sex modulates approach systems and impulsivity in substance dependence 
Drug and alcohol dependence  2013;133(1):222-227.
Personality traits such as pathological engagement in approach behaviors, high levels of impulsivity and heightened negative affect are consistently observed in substance dependent individuals (SDI). The clinical course of addiction has been shown to differ between sexes. For example, women increase their rates of consumption of some drugs of abuse more quickly than men. Despite the potential influence of personality and sex on features of addiction, few studies have investigated the interaction of these factors in substance dependence.
Fifty-one SDI (26 male, 25 female) and 66 controls (41 male, 25 female) completed the Behavioral Inhibition/Behavioral Activation System (BIS/BAS) Scales, the Barratt Impulsiveness Scale, and the Positive and Negative Affect Schedule (PANAS-X). Data were analyzed with 2×2 ANCOVAs testing for main effects of group, sex and group by sex interactions, adjusting for education level.
Significant group by sex interactions were observed for BAS scores [F(1,116)=7.03, p<.01] and Barratt Motor Impulsiveness [F(1,116)=6.11, p<.02] with female SDI showing the highest approach tendencies and impulsivity followed by male SDI, male controls, and finally female controls. SDI scored higher on negative affect [F(1,116)=25.23, p<.001] than controls. Behavioral Inhibition System scores were higher in women than men [F(1,116)=14.03, p< .001].
Higher BAS and motor impulsivity in SDI women relative to SDI men and control women suggest that personality traits that have been previously associated with drug use may be modulated by sex. These factors may contribute to differences in the disease course observed in male compared to female drug users.
PMCID: PMC3786050  PMID: 23725607
Substance dependence; sex; impulsivity; approach systems; affect
2.  Resting-state activity in the left executive control network is associated with behavioral approach and is increased in substance dependence 
Drug and alcohol dependence  2013;129(0):1-7.
Individuals with drug addictions report increased willingness to approach rewards. Approach behaviors are thought to involve executive control processes and are more strongly represented in the left compared to right prefrontal cortex. A direct link between approach tendencies and left hemisphere activity has not been shown in the resting brain. We hypothesized that compared to controls, substance dependent individuals (SDI) would have greater left hemisphere activity in the left executive control network (ECN) at rest.
Twenty-five SDI and 25 controls completed a Behavioral Inhibition System/Behavioral Activation System (BIS/BAS) questionnaire and underwent a resting-state fMRI scan. Group independent component analysis was performed. We used template matching to identify the left and right ECN separately and compared the corresponding components across groups. Across group, BAS scores were correlated with signal fluctuations in the left ECN and BIS scores with right ECN.
BAS scores were higher in SDI compared to controls (p<.003) and correlated with signal fluctuation in the left ECN. SDI showed significantly more activity than controls in the left prefrontal cortex of the left ECN. Conversely, SDI showed less activity than controls in the right prefrontal cortex of the right ECN.
Results from this study suggest that approach tendencies are related to the left ECN, even during rest. Higher resting-state signal in the left ECN may play a role in heightened approach tendencies that contribute to drug-seeking behavior.
PMCID: PMC3618865  PMID: 23428318
Substance Dependence; Approach; Avoidance; Resting-State; Executive Control Network; Laterality; BIS/BAS
3.  Negative reinforcement learning is affected in substance dependence 
Drug and Alcohol Dependence  2011;123(1-3):84-90.
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.
PMCID: PMC3292654  PMID: 22079143
Substance dependence; decision making; negative reinforcement
4.  Reduced Cortical Gray Matter Volume In Male Adolescents With Substance And Conduct Problems 
Drug and alcohol dependence  2011;118(2-3):295-305.
Boys with serious conduct and substance problems (“Antisocial Substance Dependence” (ASD)) repeatedly make impulsive and risky decisions in spite of possible negative consequences. Because prefrontal cortex (PFC) is involved in planning behavior in accord with prior rewards and punishments, structural abnormalities in PFC could contribute to a person's propensity to make risky decisions.
We acquired high-resolution structural images of 25 male ASD patients (ages 14–18 years) and 19 controls of similar ages using a 3T MR system. We conducted whole-brain voxel-based morphometric analysis (p<0.05, corrected for multiple comparisons at whole-brain cluster-level) using Statistical Parametric Mapping version-5 and tested group differences in regional gray matter (GM) volume with analyses of covariance, adjusting for total GM volume, age, and IQ; we further adjusted between-group analyses for ADHD and depression. As secondary analyses, we tested for negative associations between GM volume and impulsivity within groups and separately, GM volume and symptom severity within patients using whole-brain regression analyses.
ASD boys had significantly lower GM volume than controls in left dorsolateral PFC (DLPFC), right lingual gyrus and bilateral cerebellum, and significantly higher GM volume in right precuneus. Left DLPFC GM volume showed negative association with impulsivity within controls and negative association with substance dependence severity within patients.
ASD boys show reduced GM volumes in several regions including DLPFC, a region highly relevant to impulsivity, disinhibition, and decision-making, and cerebellum, a region important for behavioral regulation, while they showed increased GM in precuneus, a region associated with self-referential and self-centered thinking.
PMCID: PMC3170449  PMID: 21592680
Antisocial; DLPFC; Inhibition; Dependence; Precuneus; Self-referential
5.  Reducing HIV-Related Risk Behaviors Among Injection Drug Users in Residential Detoxification 
AIDS and behavior  2011;15(1):30-44.
This study of 632 drug injectors enrolled in eight residential detoxification centers within the National Drug Abuse Treatment Clinical Trials Network tested three interventions to reduce drug and sex risk behaviors. Participants were randomized to: (a) a two-session, HIV/HCV counseling and education (C&E) model added to treatment as usual (TAU), (b) a one-session, therapeutic alliance (TA) intervention conducted by outpatient counselors to facilitate treatment entry plus TAU, or (c) TAU. Significant reductions in drug and sex risk behaviors occurred for all three conditions over a 6-month follow-up period. C&E participants reported significantly greater rates of attending an HIV testing appointment, but this was not associated with better risk reduction outcomes. Reporting treatment participation within 2 months after detoxification and self-efficacy to practice safer injection behavior predicted reductions in injection risk behaviors. Findings indicate that participation in detoxification was followed by significant decreases in drug injection and risk behaviors for up to 6-months; interventions added to standard treatment offered no improvement in risk behavior outcomes.
PMCID: PMC3023839  PMID: 20652630
Drug injection; Risk reduction; Treatment entry; Detoxification
6.  Brain activation during the Stroop task in adolescents with severe substance and conduct problems: A pilot study 
Drug and alcohol dependence  2007;90(2-3):175-182.
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.
PMCID: PMC2828145  PMID: 17499456

Results 1-6 (6)