Description of Research Expertise

RESEARCH INTERESTS
Normal and abnormal goal-directed behavior. Focus on the nucleus accumbens and associated afferent and efferent circuitry. More specifically we are interested in the following: neurophysiological mechanisms that mediate the normal contribution of the nucleus accumbens and related structures to reward-directed behavior; alterations in reward-related information processing that are induced by drugs of abuse and that may underlie the development of drug addiction.


RESEARCH TECHNIQUES
Normal and abnormal goal-directed behavior. Focus on the nucleus accumbens and associated afferent and efferent circuitry. More specifically we are interested in the following: neurophysiological mechanisms that mediate the normal contribution of the nucleus accumbens and related structures to reward-directed behavior; alterations in reward-related information processing that are induced by drugs of abuse and that may underlie the development of drug addiction.

RESEARCH SUMMARY
One primary area of research aims to identify acute and lasting drug effects that may contribute to the development of drug addiction. Incentive motivation theories of drug addiction propose that the disorder reflects a pathological responsivity to the influences of drug-associated conditioned stimuli on instrumental behavior. These theories further propose that the abnormal responsivity to drug stimuli is caused by a drug-induced amplification of mechanisms that normally facilitate either stimulus-reward learning or the influence of that learning on instrumental behavior. Our research is focused on investigating this latter proposal. To carry out our investigation we use chronic extracellular recording techniques to characterize the effects of self-administered drug on neural responses to drug cues and drug-directed instrumental behavior of rats. Historically, we have focused our studies on single neuron activity within the nucleus accumbens. We are currently extending our recordings to include several accumbal afferent and efferent structures and to assess changes at a circuitry level in addition to a single neuron level. We are additionally employing a variety of new behavioral procedures to better isolate drug effects on associative processes. Planned initiatives include integration of the chronic recording studies with neuropharmacological methods and acute electrophysiological procedures to identify the neurochemicals and receptors that transduce the drug-induced changes in neural encoding of incentive-related information.

A second line of neurophysiological research is related to the proposal that drug-induced disruption of cortical inhibitory mechanisms contributes to compulsive drug seeking. In addition to the neurophysiological investigations, we have developed a behavioral research program that aims to test and refine the hypotheses that drug effects on learning-related processes and inhibitory mechanisms contribute to the development of drug-addicted behavior. A corollary of these studies is the development of more clinically relevant models of relapse. We hope that our research efforts will not only contribute to a better understanding of drug addiction, and perhaps other types of abnormal reward-directed behaviors, but also shed light on mechanisms that contribute to normal reward-directed behavior.