Impulsivity and neural systems of rewards

dc.contributor.advisorPotts, Geoffrey F.en_US
dc.creatorMartin, Laura E.en_US
dc.date.accessioned2009-06-04T06:48:26Zen_US
dc.date.available2009-06-04T06:48:26Zen_US
dc.date.issued2006en_US
dc.description.abstractBehavioral studies of decision-making in impulsive individuals demonstrate biases for immediate rewards. Decision-making includes evaluating motivational values of both options and actions. In the current studies, event related potentials (ERPs) and functional magnetic imaging (fMRI) were used to assess the temporal and spatial properties of the ventral tegmental (VTA) dopamine (DA) reward system during item evaluation and action/outcome-monitoring in impulsivity. A passive reward evaluation and an active action/outcome-monitoring task were used to test a model predicting that dysregulation of the VTA DA reward system leads to overestimations of reward value in the prefrontal cortex and underestimations of punishments in the anterior cingulate cortex (ACC) during reward evaluation and action/outcome-monitoring respectively. Passive reward evaluation ERP results showed a prefrontal P2a ERP index of reward expectation that did not differ with impulsivity. FMRI reward evaluation results indicated that the basal ganglia and left superior frontal cortex were sensitive to rewarding outcomes, whereas the medial ACC was sensitive to non-rewarding outcomes. Left superior frontal cortex fMRI activation showed greater differentiation between better than expected and worse than expected outcomes among high impulsive participants. Action/outcome-monitoring ERP results showed an ERN ERP index the ACC in the action/outcome-monitoring with the greatest response on error trials that led to punishments. The ERN was also larger among high impulsives, compared to the low impulsives, when errors led to missed rewards. The fMRI results showed that the basal ganglia responded like the ERN to errors resulting in punishments. The ACC and right middle frontal regions showed greater activation to correct responses, and a right ACC region showed larger activations when correct responses led to rewards. However, these activations did not differ with impulsivity. In conclusion, the current results suggest differential responsiveness of the mesotelencephalic reward system in impulsive individuals which may lead to reward hypersensitivity but not punishment hyposensitivity during item evaluation and action/outcome-monitoring among high impulsive participants, as seen in the left superior frontal fMRI activation during item evaluation and in the ACC ERP activity during outcome-monitoring. Differences between the ERP and fMRI results may reflect the different physiological processes that give rise to the signals.en_US
dc.format.extent156 p.en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.callnoTHESIS PSYCH. 2006 MARTINen_US
dc.identifier.citationMartin, Laura E.. "Impulsivity and neural systems of rewards." (2006) Diss., Rice University. <a href="https://hdl.handle.net/1911/18945">https://hdl.handle.net/1911/18945</a>.en_US
dc.identifier.urihttps://hdl.handle.net/1911/18945en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectCognitive psychologyen_US
dc.titleImpulsivity and neural systems of rewardsen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentPsychologyen_US
thesis.degree.disciplineSocial Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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