Changes in brain networks involved in reward processing during abstinence from cigarettes

Open Access
Author:
Nichols, Travis Tyler
Graduate Program:
Psychology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 27, 2016
Committee Members:
  • Stephen Jeffrey Wilson, Dissertation Advisor
  • Stephen Jeffrey Wilson, Committee Chair
  • Frank Gerard Hillary, Committee Member
  • Charles Geier, Committee Member
  • Peter Cm Molenaar, Outside Member
Keywords:
  • fMRI
  • cigarettes
  • smoking
  • brain networks
  • connectivity
  • addiction
  • beta series
  • reward processing
Abstract:
Dysregulated reward processing in addiction is characterized by overvaluing drug stimuli and undervaluing other rewards (e.g., sex, food, money, etc.). Research suggests this may play a critical role in compulsive drug use and risk for relapse. We attempted to induce two different types of monetary reward devaluation in two studies of chronic cigarette smokers (Study 1: expectation to smoke, Study 2: monetary rewards viz-a-viz. cigarette rewards). Though this manipulation did not result as expected, we did observe predicted ventromedial striatal activation in response to reward in Study 1, and an unexpected increase in pre-SMA response to punishment in both studies. The latter effect was interpreted to represent the integration of negative feedback with the behavioral choice that incurred the loss. We were mainly interested in brain network changes involved in imbalanced reward processing and we utilized the recently developed beta series technique to compare connectivity between conditions. In Study 1, this revealed a main effect of time that was disparate from the univariate analysis and suggested that reward processing becomes more efficient with continued use (as evidenced by reduced univariate activation and increased connectivity with other regions). A time by outcome interaction between the bilateral ventromedial striatum was observed, such that connectivity was greater for pre-shift punishment trials and post-shift reward trials. One interpretation of this effect is that participants shifted their priority from avoiding punishment to pursuing reward over time. To our knowledge, this represents the first attempt to explore brain networks subserving reward devaluation in drug use. Future endeavors should carefully consider the experimental design that will maximally juxtapose “normal” vs. devalued reward processing, as well as the best way to assess connectivity.