ROLE OF THE NUCLEUS ACCUMBENS AND ITS DOPAMINERGIC AND GLUTAMATERGIC AFFERENTS DURING DELAY DISCOUNTING

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  • March 19, 2019
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  • Rodeberg, Deirdre
    • Affiliation: College of Arts and Sciences, Department of Psychology and Neuroscience
Abstract
  • Effective decision making depends on an organism’s ability to assess available resources and choose the best available option. Organisms must also assess changes to reward value and update their behavior accordingly to keep selecting the best option. Value-based decision making depends on neural pathways including the nucleus accumbens (NAc) and its dopaminergic input from the ventral tegmental area (VTA). A glutamatergic afferent to the NAc core, the prelimbic cortex (PrL), may also be implicated in value-based decision-making, such as delay discounting. However, it is unknown how these dopaminergic and glutamatergic afferents to the NAc mediate value-based decision-making behavior. First, I used optogenetic techniques to examine the causal role of dopaminergic input to the NAc during delay discounting decision making tasks. This experiment revealed that dopamine release in the NAc core does not mediate delay discounting. The next set of experiments shifted focus to the PrL’s glutamatergic ennervation of the NAc. Electrophysiological recording of the PrL during our delay discounting task revealed that PrL neurons track the predicted and eventual outcome of preferred rewards, as the value of that reward shifts across blocks. Further, this tracking differentially encoded preferred rewards depending on rats’ inherent impulsivity, such that high impulsive rats demonstrated preferential encoding of the small/immediate option. In the next experiment, optogenetic stimulation of the PrL-NAc core pathway revealed that glutamate signaling in the NAc core was not sufficient to mediate delay discounting. Together, these experiments help to characterize of the neural circuits and mechanisms by which delay discounting behavior is processed within the brain, providing insight into the potential role of the NAc and its dopaminergic and glutamatergic afferents in mediating appropriate decisions.
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  • Carelli, Regina
  • Thiele, Todd
  • Reissner, Kathryn
  • Hollins, Mark
  • Lysle, Donald
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2018
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