Mesolimbic dopamine is considered to have a major role in Pavlovian reward learning. Pavlovian reward learning processes underlie many aspects of drug seeking behavior and may play a critical role in drug relapse. Hence our overall goal is to better understand the basic neurobehavioral mechanisms of reward learning. Here we seek to better define that role using optogenetic tools that will allow precise control of dopamine neuron activity during behavior. We will use the Th:Cre rat, a transgenic rat expressing Cre recombinase under control of a tyrosine hydroxylase (Th) promoter that allows for gene expression limited to dopamine neurons in the VTA following infusion of cre-dependent viruses expressing either channelrhodopsin or halorhodopsin. We can then deliver light through optical fibers surgically implanted into the VTA in the behaving rat to activate or inhibit activity of DA neurons. The proposed studies are based upon the notion that 1) dopamine neuron activity during the receipt of unexpected reward drives new learning about cues that predict the availability that reward, and that 2) decreases in dopamine neuron activity during expected reward may contribute to extinction of responding to reward-predictive cues. Thus we propose to extend preliminary findings to show that increases in dopamine neuron activity induced by optical stimulation functions as a positive prediction error and can cause learning. We also will test the hypothesis that suppression of dopamine neuron activity by optical stimulation functions as a negative prediction error and decreases learned responding. Additionally, we will test the hypothesis that these effects are mediated by dopamine neurons that project to the nucleus accumbens. Hence, using well-characterized Pavlovian conditioning procedures in combination with state-of- the-art behavioral optogenetics, the current aims are designed to expand our understanding of causal roles for VTA DA neuron activity in reward learning.
Because Pavlovian reward learning processes underlie many aspects of drug seeking behavior, and may play a critical role in drug relapse, we are interested in understanding the basic neurobehavioral mechanisms of reward learning. The neurotransmitter, dopamine, plays a major role in Pavlovian reward learning, but the specific means are unclear. Here we seek to better define that role using optogenetic tools in rats that allow precise control of dopamine neuron activity during behavior to expand our understanding of causal roles for VTA DA neuron activity in reward learning, thereby allowing for a deeper understanding of this process in normal and pathological behavior.
|Ottenheimer, David; Richard, Jocelyn M; Janak, Patricia H (2018) Ventral pallidum encodes relative reward value earlier and more robustly than nucleus accumbens. Nat Commun 9:4350|
|Fischbach-Weiss, Sarah; Reese, Rebecca M; Janak, Patricia H (2018) Inhibiting Mesolimbic Dopamine Neurons Reduces the Initiation and Maintenance of Instrumental Responding. Neuroscience 372:306-315|
|Saunders, Benjamin T; Richard, Jocelyn M; Margolis, Elyssa B et al. (2018) Dopamine neurons create Pavlovian conditioned stimuli with circuit-defined motivational properties. Nat Neurosci 21:1072-1083|
|Fraser, Kurt M; Janak, Patricia H (2017) Long-lasting contribution of dopamine in the nucleus accumbens core, but not dorsal lateral striatum, to sign-tracking. Eur J Neurosci 46:2047-2055|
|Millan, E Zayra; Kim, H Amy; Janak, Patricia H (2017) Optogenetic activation of amygdala projections to nucleus accumbens can arrest conditioned and unconditioned alcohol consummatory behavior. Neuroscience 360:106-117|
|Janak, Patricia H; Tye, Kay M (2015) From circuits to behaviour in the amygdala. Nature 517:284-92|
|Saunders, Benjamin T; Richard, Jocelyn M; Janak, Patricia H (2015) Contemporary approaches to neural circuit manipulation and mapping: focus on reward and addiction. Philos Trans R Soc Lond B Biol Sci 370:20140210|
|Keiflin, Ronald; Janak, Patricia H (2015) Dopamine Prediction Errors in Reward Learning and Addiction: From Theory to Neural Circuitry. Neuron 88:247-63|
|Steinberg, Elizabeth E; Boivin, Josiah R; Saunders, Benjamin T et al. (2014) Positive reinforcement mediated by midbrain dopamine neurons requires D1 and D2 receptor activation in the nucleus accumbens. PLoS One 9:e94771|