Education

Ph.D. Experimental Psychology, Behavioral Neuroscience Program, Rutgers University, New Brunswick, NJ, 1991.

M.S. Experimental Psychology, Behavioral Neuroscience Program, Rutgers University, New Brunswick, NJ, 1987.

B.A. Psychology/English, Rutgers University (Rutgers College), Departmental Honors (Highest Distinction) in Psychology. New Brunswick, NJ, 1984.

Research Interests

Why are drugs of abuse such as cocaine so addictive? How can cues associated with prior drug use in human addicts (e.g., drug paraphernalia) elicit such powerful drug craving following months or even years of drug abstinence?  Is it true that addictive compounds like cocaine “hijack” the parts of the brain that evolved to recognize and consume ‘natural’ rewards like food and water?

These are some of the questions that drive my research program at UNC.  My primary research interests are to understand how the brain processes information about natural (nondrug) rewards, and how drugs of abuse such as cocaine alter this system and lead to addiction.  Numerous investigations have demonstrated that the rewarding properties of abused substances such as cocaine and ‘natural’ reinforcers such as food, water, and sweets (e.g., sucrose) are mediated by the brain’s ‘reward system’, which includes the nucleus accumbens (NAc) and its dopaminergic input.  Further, there is evidence that many of the neural circuits involved in associative learning and decision making, such as pathways from the basolateral amygdala and higher cortical areas, are also recruited and modulated by drugs of abuse. Ongoing investigations in my lab employ a number of cutting-edge techniques to elucidate how these brain regions, and connections between these regions, contribute to reward-related behaviors that involve Pavlovian and operant conditioning, cocaine-self administration, higher-order conditioning, and decision making.  Several cutting-edge techniques are used alone, or in combination, in awake and behaving rats to elucidate robust physiological correlates of reward-seeking behavior.  These techniques include:

Electrophysiological Recording: We use multi-neuron recording techniques to monitor extracellular neural activity in targeted brain regions during behavior. This approach allows us to link neuronal firing patterns that occur in various brain regions to specific reward-related behaviors.

Electrochemistry:  Fast-scan cyclic voltammetry is an electrochemical technique that we use in behaving rats to detect rapid (subsecond) dopamine release in the NAc with unprecedented temporal and spatial resolution.

Combined Electrophysiology/Electrochemistry: Working in collaboration with Dr. R. Mark Wightman (UNC Chemistry) we use a method that combines electrophysiological and electrochemical tools to simultaneously monitor extracellular activity and rapid dopamine release events.  Further, causal links between cell firing and subsecond dopamine signaling are determined using pharmacological tools and/or iontophoretic drug delivery during behavior.

Optogenetics: Optogenetic tools utilizing genetic and viral targeting of light-activated ion pumps or channels (opsins) allow for temporally precise modulation of cell-type and circuit-specific neural populations. Working in collaboration with Dr. Garret Stuber (UNC Psychiatry) we apply this advanced method to understand neurobiological circuits underlying reward-related behaviors in rats.

Some Ongoing Research Projects:  Currently, members of my lab are using these methods to investigate several specific research topics. For example, some studies are examining the influence of cocaine abstinence on cocaine-seeking behavior, correlated cell firing and dopamine release dynamics in the NAc.  Other studies are examining neurobiological mechanisms mediating the emergence of negative affective states in cocaine addiction, and the associated devaluation of natural rewards. Additionally, my lab is investigating the dynamic properties of NAc dopamine release during decision-making behavior, and how optogenetic modulations of dopamine release may influence decision-making in real-time. Finally, recent investigations are using optogenetics to selectively modulate glutamatergic NAc afferent pathways in order to dissect specific neural regions underlying various aspects of reward-seeking behavior.

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