The Virtual Personalities Model is a motive-based neural network model that provides both a psychological model and a computational implementation that explicates the dynamics and often large within-person variability in behavior that arises over time. At the same time the same model can produce—across many virtual personalities—between-subject variability in behavior that when factor analyzed yields familiar personality structure (e.g., the Big Five). First, we describe our personality model and its implementation as a neural network model. Second, we focus on detailing the neurobiological underpinnings of this model. Third, we examine the learning mechanisms, and their biological substrates, as ways that the model gets “wired up,” discussing Pavlovian and Instrumental conditioning, Pavlovian to Instrumental transfer, and habits. Finally, we describe the dynamics of how initial differences in propensities (e.g., dopamine functioning), wiring differences due to experience, and other factors could operate together to develop and change personality over time, and how this might be empirically examined. Thus, our goal is to contribute to the rising chorus of voices seeking a more precise neurobiologically based science of the complex dynamics underlying personality.

Introduction: Attention-deficit/hyperactivity disorder (ADHD) is a serious neurobehavioral disorder of childhood onset that often persists into adolescence and adulthood. Functional impairments, underachievement, and difficult interpersonal relationships illustrate the need for effective treatment of ADHD through adulthood.

Method: This prospective, multisite, randomized, double-blind, placebo-controlled, parallel-group, dose-escalation study was conducted to assess the efficacy, safety, and duration of action of mixed amphetamine salts extended-release (MAS XR) in adults with ADHD, combined type. Adults ≥ 18 years of age were given placebo or MAS XR 20, 40, or 60 mg/day for 4 weeks. The main outcome measures were the ADHD Rating Scale and Conners' Adult ADHD Rating Scale Short Version Self-Report (CAARS-S-S).

Results: Two hundred fifty-five subjects were randomly assigned to treatment with MAS XR or placebo. MAS XR treatment was associated with statistically and clinically significant ADHD symptom reduction at endpoint; mean ADHD Rating Scale scores were 18.5 for the 20-mg group (P=.001), 18.4 for the 40-mg group (P<.001), and 18.5 for the 60-mg group (P<.001). Adults with severe symptoms (ADHD Rating Scale score ≥32 at baseline) had significantly greater symptom reduction with the highest MAS XR dose (60 mg/day), however, this dose-response relationship was determined by post-hoc analysis. The mean MAS XR effect size was 0.8. Statistically significant (P<.05) improvements in CAARS-S-S ADHD index scores occurred at 4- and 12-hours postdose for all MAS XR groups, indicating a 12-hour duration of effect. Symptoms improved within the first treatment week. Most adverse events reported were mild or moderate in intensity, arid the most commonly reported adverse events were consistent with the known profile of stimulant medications. Vital signs and electrocardiograms showed no clinically significant cardiovascular changes.

Conclusion: These results suggest that MAS XR is safe and effective in adults with ADHD and controlled ADHD symptoms for up to 12 hours.