Dopamine neurons of the ventral tegmental area (VTA) are critical for the processing of reward-related information and for the learning of associations between cues and rewards. Dopamine neurons alternate between tonic firing (1-4 Hz), and burst firing (10-20 Hz). Dopamine neurons burst in response to an unexpected reward. However, after repeated, contingent pairings between a neutral cue and a reward, the dopamine neuron transfers burst firing to the neutral cue, or conditioned stimulus. I am interested in the mechanisms that underlie the development of the conditioned burst response, and the way in which environmental experience can shape this type of learning.
To answer these questions, I use a combination of in vitro brain slice electrophysiology as well as behavioral paradigms such as conditioned place preference to determine the effect of early environmental experience on calcium signaling and plasticity in dopamine neurons. The animals that I study are raised in a socially isolated environment during the early adolescent period. Interestingly, socially isolated animals have alterations in calcium signaling and drug reward learning compared to animals raised in a normal social environment. Future experiments will determine a mechanism underlying these changes in an effort to learn more about environmentally-mediated changes in addiction vulnerability.
Bernier BE, Whitaker LR, Morikawa H (2011). Previous ethanol experience enhances synaptic plasticity of NMDA receptors in the ventral tegmental area. J Neurosci 31:5205-5212. PubMed