nihms-1545155

Page 1: Introduction and Background

  • Background:

    • Chronic cocaine use linked to structural brain abnormalities, especially in the prefrontal cortex (PFC), implicated in impulsivity.

    • The study explores the relationship between gray matter volume (GMV) reductions and impulsivity in current cocaine users (COC+) versus controls (COC−).

  • Methods:

    • Participants: 39 active cocaine users (COC+) and 40 controls (COC−).

    • Brain Scanning: MRI scans conducted on a 3T MRI machine.

    • Measures: Assessed trait impulsivity and delayed reward discounting outside of the scanner.

    • Analysis Technique: Used whole-brain voxel-based morphometry for GMV comparisons.

  • Results:

    • COC+ displayed significant GMV reductions in frontal, parietal, occipital, and cerebellar regions.

    • Lower GMV associated with higher trait impulsivity in lateral PFC and delayed reward discounting in medial PFC, as well as both measures in the posterior parietal cortex.

    • COC+ exhibited higher impulsivity on all measures compared with COC−.

  • Conclusions:

    • Trait and behavioral measures of impulsivity show different correlations with brain morphology despite similar patterns in both COC+ and COC−.

Page 2: Impulsivity and Decision-Making

  • Behavioral Measures:

    • Explicit assessment of impulsivity processes; delayed reward discounting refers to valuing rewards less when they are delayed.

    • Tasks involve preferences for immediate versus delayed rewards.

  • Findings:

    • Cocaine users exhibit greater impulsivity across traits and delayed reward discounting than non-users.

    • Impulsivity connected to abnormalities in the mesocorticolimbic system and reduced GMV.

    • Healthy adults show reduced GMV in medial frontal regions associated with trait impulsivity and in lateral PFC for delayed discounting.

Page 3: Brain Structural Abnormalities

  • Cocaine and the Mesocorticolimbic System:

    • Literature reveals GMV reductions in PFC regions among cocaine users, affecting decision-making and impulsive behavior.

    • Previous studies show variations relating impulsivity to differing brain regions; two correlations between trait impulsivity and brain volume have been found in past studies.

  • Study Goals:

    • Investigate how cocaine affects GMV and its relation to impulsivity, hypothesize reduced GMV in PFC and increased in striatum within cocaine users.

Page 4: Participant Criteria

  • Inclusion Criteria for COC+ Group:

    • Lifetime cocaine dependence, regular use for ≥1 year, use within the last month, and cocaine as primary substance.

  • COC− Group:

    • No history of cocaine use or related disorders, cocaine-negative drug screen, and certain exclusions for other substances and neurological issues.

Page 5: Procedures

  • Recruitment:

    • Participants recruited via advertisements, followed by telephone screenings and in-person assessments before MRI.

  • Screening Measures:

    • Confirmed blood alcohol levels and various substance use assessments including drugs used over the last month.

Page 6: Behavioral Assessments

  • Substance Use Measurement:

    • Breathalyzer tests and follow-back methodology for assessing substance use over 30 days.

  • Trait Impulsivity Assessment:

    • Barratt Impulsivity Scale (BSI-11) encompasses non-planning, attentional, and motor impulsivity traits through a self-report questionnaire.

Page 7: MRI Data Acquisition and Analysis

  • MRI Protocol:

    • Scanned using a 3.0T GE Discovery MR750 scanner with specific image parameters.

  • Processing:

    • Images were brain-extracted, registered to standard space, filtered, and analyzed for GMV.

Page 8: Results

  • Sample Characteristics:

    • Cohort demographics including age, gender, race, and education.

    • Higher trait impulsivity scores and usage rates documented in COC+ group.

Page 9: Group Differences in GM Volume

  • Whole-Brain Analysis Outcomes:

    • Significant differences in GMV noted in several clusters across the brain, particularly in anterior and posterior regions.

  • Impulsivity Correlation:

    • Voxel-wise correlations of GMV with measures of impulsivity highlighted associations in prefrontal and parietal cortices.

Page 10: Discussion of Findings

  • Key Finding:

    • Alterations in GMV from cocaine use correlate with impulsivity measures.

    • Structural brain abnormalities emerge in key areas associated with impulsivity, affirming prior research.

  • Self-reporting vs. Behavioral Measures:

    • Differentiation between assessed impulsivity types illustrates the need for combining measures for thorough understanding in clinical settings.

Page 15: Study Highlights

  • Key Findings:

    • Cocaine users experience notable reductions in GMV associated with impulsivity.

    • Study emphasizes the multifaceted nature of impulsivity and its structural basis in both clinical and non-clinical populations.