Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (18 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2012)

Cocaine addiction affects approximately 1.4 million Americans, costing the government billions of dollars and the addicted individual their life. Addiction is characterized by a continued desire to use a drug despite decreased enjoyment from taking it and a desire to abstain. Multiple theories attempt to explain how prolonged drug use induces the chronic brain changes that result in addiction. The incentive sensitization theory suggests that repeated exposure to drugs of abuse alters the neural circuitry that is involved in incentive motivation, the process that allows drugs and their associated stimuli to more strongly encourage drug-seeking behavior. Alternatively, the habit learning theory suggests that drugs of abuse pathologically subvert the reward-learning circuitry, leading to compulsive drug seeking triggered by drug-associated stimuli. Since both theories are based on the idea that drugs of abuse affect the dopaminergic system and alter normal reward processing, it has been proposed that drug exposure may also affect behavior for natural rewards.

To understand the mechanisms by which cocaine use modifies reward-seeking behaviors, I have conducted experiments to investigate both addiction theories using cocaine and food rewards as the outcome. I have found that cocaine-paired cues promote cocaine-seeking and taking actions via a Pavlovian motivational mechanism. I have also explored the importance of the contingency of drug delivery and found that cocaine has a general effect on incentive motivation, with both self-administered and experimenter-delivered cocaine enhancing the ability of food-paired cues to motivate food-seeking behavior. This result was not obtained with animals that passively received cocaine infusions, suggesting a role of predictability in the effects of cocaine on incentive motivation.

I have also found support for the habit learning theory, demonstrating that cocaine treatment can encourage habitual control of action selection for food rewards, even when feedback is given. However, experimenter-delivered cocaine does not prevent animals from learning to perform a behavior in a goal-directed fashion. Our results lend support to both theories, suggesting that drug induced changes to the dopaminergic systems may be affecting both incentive motivation and reward learning. These results have important implications for our comprehension of the neural processes involved in addiction.

    Cover page: A Tale of Two Addiction Theories: the effects of cocaine exposure on cue-induced motivation and action control
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2014)
    Drug addiction is marked by pathological drug seeking and intense drug craving, particularly in response to drug-related stimuli. Repeated psychostimulant administration is known to induce long-term alterations in mesolimbic dopamine (DA) signaling that are hypothesized to mediate this heightened sensitivity to environmental stimuli. However, there is little direct evidence that drug-induced alteration in mesolimbic DA function underlies this hypersensitivity to motivational cues. In the current study, we tested this hypothesis using fast-scan cyclic voltammetry to monitor phasic DA signaling in the nucleus accumbens core of cocaine-pretreated (6 once-daily injections of 15 mg/kg, i.p.) and drug-naive rats during a test of cue-evoked incentive motivation for food-the Pavlovian-to-instrumental transfer task. We found that prior cocaine exposure augmented both reward seeking and DA release triggered by the presentation of a reward-paired cue. Furthermore, cue-evoked DA signaling positively correlated with cue-evoked food seeking and was found to be a statistical mediator of this behavioral effect of cocaine. Taken together, these findings provide support for the hypothesis that repeated cocaine exposure enhances cue-evoked incentive motivation through augmented phasic mesolimbic DA signaling. This work sheds new light on a fundamental neurobiological mechanism underlying motivated behavior and its role in the expression of compulsive reward seeking.
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2013)
      There is growing evidence that mere exposure to drugs can induce long-term alterations in the neural systems that mediate reward processing, motivation, and behavioral control, potentially causing the pathological pursuit of drugs that characterizes the addicted state. The incentive sensitization theory proposes that drug exposure potentiates the influence of reward-paired cues on behavior. It has also been suggested that drug exposure biases action selection towards the automatic execution of habits and away from more deliberate goal-directed control. The current study investigated whether rats given repeated exposure to peripherally administered cocaine would show alterations in incentive motivation (assayed using the Pavlovian-to-instrumental transfer (PIT) paradigm) or habit formation (assayed using sensitivity to reward devaluation). After instrumental and Pavlovian training for food pellet rewards, rats were given 6 daily injections of cocaine (15 mg/kg, IP) or saline, followed by a 10-d period of rest. Consistent with the incentive sensitization theory, cocaine-treated rats showed stronger cue-evoked lever pressing than saline-treated rats during the PIT test. The same rats were then trained on a new instrumental action with a new food pellet reward before undergoing a reward devaluation testing. Although saline-treated rats exhibited sensitivity to reward devaluation, indicative of goal-directed performance, cocaine-treated rats were insensitive to this treatment, suggesting a reliance on habitual processes. These findings, when taken together, indicate that repeated exposure to cocaine can cause broad alterations in behavioral control, spanning both motivational and action selection processes, and could therefore help explain aberrations of decision-making that underlie drug addiction.
        Cover page: Repeated Cocaine Exposure Facilitates the Expression of Incentive Motivation and Induces Habitual Control in RatsCreative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2021)
        Genetic results have implications not only for the individual, but also for their family members. Research on family communication of genetic results has primarily focused on families affected by adult-onset, dominant conditions as well as more common genetic conditions such as familial hypercholesterolemia, cardiomyopathies, and genetic hearing loss. This study therefore aimed to characterize genetic result communication in families with rare and undiagnosed conditions and identify factors that influence communication. One hundred and forty-two individuals who received a diagnosis from the Undiagnosed Diseases Network (UDN), a study focused on providing diagnoses to individuals with undiagnosed conditions, were eligible to complete a survey assessing genetic results communication. Survey items assessed if communication was discussed with healthcare providers, with whom participants communicated genetic testing, why they chose to communicate with these family members, and what information they communicated. All respondents (5 adult UDN participants, 38 parents/guardians of UDN participants, and 2 identifying as both) shared genetic results with at least one family member. Individuals who identified as both were considered exclusively adult participants for the purpose of these analyses. Adult participants and parents/guardians of participants reported high levels of understanding (96%), utility (96%), and comfort communicating genetic results (89%). Additionally, parents/guardians were more likely to disclose genetic results due to a general desire to share (60% of parents/guardians vs. 14% adult participants), while adult participants reported that they shared results to communicate risk to family members (86% of adult participants vs. 24% of parents/guardians). Many respondents did not recall discussing with a healthcare provider how (64%) or what (42%) to communicate about results. The results of this study provide insight into the practice of result communication by individuals with rare and previously undiagnosed conditions, which can ideally inform development of more effective counseling strategies and guidelines to aid family communication.
          Cover page: Family genetic result communication in rare and undiagnosed disease communities: Understanding the practice.
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2022)

          Background

          Although a relatively large body of research has identified multiple factors associated with adolescent substance use, less is known about earlier substance-related factors during preadolescence, including curiosity to use substances. The present study examined individual-, peer-, and parent-level domains pertaining to substance use and how these domains vary by sociodemographic subgroups and substance type.

          Methods

          Participants were 11,864 9- and 10-year-olds from the baseline sample of the Adolescent Brain Cognitive Development (ABCD) Study. Youth-reported measures were curiosity to use substances and perceived peer substance use. Parent-reported measures were availability of and rules about substances. Generalized logistic mixed models (GLMM) were used to compare these measures across alcohol, nicotine, and marijuana and across sociodemographic subgroupings (sex, race/ethnicity, household income, and family history of alcohol problems). GLMM was then used to examine predictors of curiosity to use by substance type.

          Results

          The most striking descriptive differences were found between race/ethnicity and income categories (e.g., positive associations between greater income and greater availability of alcohol). In multivariable analyses, greater curiosity to use alcohol was associated with being male, higher household income, perceived peer alcohol use, and easy alcohol availability; greater curiosity to use nicotine was associated with being male, perceived peer cigarette use, easy availability of cigarettes, and no parental rules about cigarette use.

          Conclusions

          This study identified substance use-related individual-, peer-, and parent-level factors among a diverse, national sample. Findings highlight the importance of considering sociodemographic and substance-specific variability and may help identify risk and protective factors preceding adolescent substance use.
            Cover page: Individual-, peer-, and parent-level substance use-related factors among 9- and 10-year-olds from the ABCD Study: Prevalence rates and sociodemographic differences
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2018)
            The burden of living with an undiagnosed condition is high and includes physical and emotional suffering, frustrations, and uncertainty. For patients and families experiencing these stressors, higher levels of empowerment may be associated with better outcomes. Thus, it is important to understand the experiences of patients with undiagnosed conditions and their families affected by undiagnosed conditions in order to identify strategies for fostering empowerment. In this study, we used the Genetic Counseling Outcome Scale (GCOS-24) to assess levels of empowerment and support group participation in 35 adult participants and 67 parents of child participants in the Undiagnosed Diseases Network (UDN) prior to their UDN in-person evaluation. Our results revealed significantly lower empowerment scores on the GCOS-24 in adult participants compared to parents of child participants [t(100) = - 3.01, p = 0.003, average difference = - 11.12, 95% CI (- 3.78, - 18.46)] and no significant association between support group participation and empowerment scores. The majority of participants (84.3%, 86/102) are not currently participating in any support groups, and participation rates were not significantly different for adult participants and parents of child participants (11.4 vs. 19.7%, respectively, FE p = 0.40). Open-ended responses provided additional insight into support group participation, the challenges of living with undiagnosed conditions, and positive coping strategies. Future research will evaluate the extent to which empowerment scores change as participation in the UDN unfolds.
              Cover page: Understanding Adult Participant and Parent Empowerment Prior to Evaluation in the Undiagnosed Diseases Network.
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2022)
              The Adolescent Brain Cognitive Development (ABCD)SM study aims to retain a demographically diverse sample of youth and one parent across 21 sites throughout its 10-year protocol while minimizing selective (systematic) attrition. To evaluate the effectiveness of these efforts, the ABCD Retention Workgroup (RW) has employed a data-driven approach to examine, track, and intervene via three key metrics: (1) which youth completed visits late; (2) which youth missed visits; and (3) which youth withdrew from the study. The RW actively examines demographic (race, education level, family income) and site factors (visit satisfaction, distance from site, and enrollment in ancillary studies) to strategize efforts that will minimize disengagement and loss of participating youth and parents. Data showed that the most robust primary correlates of late visits were distance from study site, race, and parental education level. Race, lower parental education level, parental employment status, and lower family income were associated with higher odds of missed visits, while being enrolled in one of the ancillary studies was associated with lower odds of missed visits. Additionally, parents who were primary Spanish speakers withdrew at slightly higher rates. These findings provide insight into future targets for proactive retention efforts by the ABCD RW.
                Cover page: Measuring retention within the adolescent brain cognitive development (ABCD)SM study
                • Article
                • Peer Reviewed
                UCLA Previously Published Works (2021)

                Purpose

                Genomic sequencing has become an increasingly powerful and relevant tool to be leveraged for the discovery of genetic aberrations underlying rare, Mendelian conditions. Although the computational tools incorporated into diagnostic workflows for this task are continually evolving and improving, we nevertheless sought to investigate commonalities across sequencing processing workflows to reveal consensus and standard practice tools and highlight exploratory analyses where technical and theoretical method improvements would be most impactful.

                Methods

                We collected details regarding the computational approaches used by a genetic testing laboratory and 11 clinical research sites in the United States participating in the Undiagnosed Diseases Network via meetings with bioinformaticians, online survey forms, and analyses of internal protocols.

                Results

                We found that tools for processing genomic sequencing data can be grouped into four distinct categories. Whereas well-established practices exist for initial variant calling and quality control steps, there is substantial divergence across sites in later stages for variant prioritization and multimodal data integration, demonstrating a diversity of approaches for solving the most mysterious undiagnosed cases.

                Conclusion

                The largest differences across diagnostic workflows suggest that advances in structural variant detection, noncoding variant interpretation, and integration of additional biomedical data may be especially promising for solving chronically undiagnosed cases.
                  Cover page: Commonalities across computational workflows for uncovering explanatory variants in undiagnosed cases.
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2021)
                  The Adolescent Brain Cognitive Development (ABCD) Study of 11,880 youth incorporates a comprehensive range of measures assessing predictors and outcomes related to mental health across childhood and adolescence in participating youth, as well as information about family mental health history. We have previously described the logic and content of the mental health assessment battery at Baseline and 1-year follow-up. Here, we describe changes to that battery and issues and clarifications that have emerged, as well as additions to the mental health battery at the 2-, 3-, 4-, and 5-year follow-ups. We capitalize on the recent release of longitudinal data for caregiver and youth report of mental health data to evaluate trajectories of dimensions of psychopathology as a function of demographic factors. For both caregiver and self-reported mental health symptoms, males showed age-related decreases in internalizing and externalizing symptoms, while females showed an increase in internalizing symptoms with age. Multiple indicators of socioeconomic status (caregiver education, family income, financial adversity, neighborhood poverty) accounted for unique variance in both caregiver and youth-reported externalizing and internalizing symptoms. These data highlight the importance of examining developmental trajectories of mental health as a function of key factors such as sex and socioeconomic environment.
                    Cover page: Demographic and mental health assessments in the adolescent brain and cognitive development study: Updates and age-related trajectories
                    • Article
                    • Peer Reviewed
                    UC San Diego Previously Published Works (2021)
                    Physical health in childhood is crucial for neurobiological as well as overall development, and can shape long-term outcomes into adulthood. The landmark, longitudinal Adolescent Brain Cognitive Development StudySM (ABCD study®), was designed to investigate brain development and health in almost 12,000 youth who were recruited when they were 9-10 years old and will be followed through adolescence and early adulthood. The overall goal of this paper is to provide descriptive analyses of physical health measures in the ABCD study at baseline, including but not limited to sleep, physical activity and sports involvement, and body mass index. Further this summary will describe how physical health measures collected from the ABCD cohort compare with current normative data and clinical guidelines. We propose this data set has the potential to facilitate clinical recommendations and inform national standards of physical health in this age group. This manuscript will also provide important information for ABCD users and help guide analyses investigating physical health including new avenues for health disparity research as it pertains to adolescent and young adult development.
                      Cover page: A Comprehensive Overview of the Physical Health of the Adolescent Brain Cognitive Development Study Cohort at BaselineCreative Commons 'BY' version 4.0 license
                      Top