Dr. Larry Hawk

Summary of Research Interests:

My research focuses on basic motivational and cognitive processes, the disruption of these processes in psychopathology, and the role of these processes in effective interventions. My work takes a three-system perspective, examining behavioral, subjective, and psychophysiological measures (startle and other EMG measures, and, more recently, ERPs). Much of the current work in my lab is organized around two seemingly disparate areas - cigarette smoking and ADHD - that are actually joined by conceptual, neurobiological, and clinical ties.

The smoking work has several aspects. Two recent small trials (one NCI-funded; the other industry-funded) examined the role of learning processes (i.e., extinction) in the effectiveness of pharmacotherapy (bupropion and varenicline) for smoking cessation. In the context of that clinical trial, we are also examining multiple indices of cue reactivity and cognitive effects of the medication (led by Jessica Rhodes, doctoral student). My colleagues and I are also just beginning a newly-funded (NIDA) multi-site randomized clinical trial (U Pennsylvania, U Toronto, MD Anderson Cancer Center, Roswell Park Cancer Institute) to examine the degree to which pharmacotherapy (varenicline and NRT) for cessation is influenced by individual differences in nicotine metabolism, measured by a genetically-informed phenotypic marker. We will once again explore a number of basic science questions within the context of this large clinical study. Recent and ongoing basic science studies include the effects of smoking abstinence on measures of impulsivity among participants high and low in ADHD symptoms (led by Rebecca Ashare, doctoral student) and the effects of abstinence and monetary incentives on ERP aspects of error-processing (led by Nick Schlienz, doctoral student). The overall goal of this program of research is to better understand the role of basic psychological processes in the onset and maintenance of smoking, as well as treatment response, and to facilitate translation of these findings into improved treatments for nicotine dependence.

Regarding ADHD, we are again focusing on the basic neurocognitive and motivational processes involved in the psychopathology of the disorder, as well as in the mechanisms of treatment response. In a large-scale NIMH-funded study, we are examining the basic neurocognitive processes (e.g., response inhibition, delayed discounting, working memory, sustained attention) through which methylphenidate improves classroom performance in ADHD. This project is the first to test the extent to which stimulant effects on basic processes assessed in the lab actually mediate, or account for, individual differences in clinical response to stimulant medication. This research has also led to a number of recent publications led by doctoral students, including studies of prepulse inhibition of startle (Rebecca Ashare et al., 2010), delay-related impulsivity (Keri Shiels et al., 2009), and intra-individual variability (Sarah Spencer et al., 2009). In a series of lab studies, we are also testing the effects of motivational incentives on cognitive performance in children with and without ADHD, including working memory (Keri Shiels et al., 2008; Mike Strand et al., in prep), intra-individual variability (Michelle Bubnik et al., in prep.), and, most recently, ERP aspects of error-processing and self-regulation (Keri Shiels and Hawk, 2010; in prep).

Currently, in collaboration with Dr. Greg Fabiano, we are also collecting neurocognitive data on teenage-drivers with ADHD, and we have just submitted a grant application on this topic. The aims would be to test the neurocognitive mechanisms that lead to substantially worse driving outcomes for teens with ADHD and to determine the extent to which basic cognitive processes moderate treatment outcome.

Updated 1/24/1