All ETDs from UAB

Advisory Committee Chair

Rosalyn Weller

Advisory Committee Members

James Cox

Thane Wibbels

Document Type

Thesis

Date of Award

2011

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

Obesity is a serious public health issue. Obesity may be accompanied by abnor-malities in executive function circuitry related to impulsivity. A useful task for studying impulsivity is the delay discounting (DD) of money task, in which an individual chooses in a series of trials between an immediate and a delayed, but greater, amount of money. On the DD task, individuals with various addictions make more immediate than delayed choices, compared to controls. Similar results have been observed in obese compared to healthy-weight women. Functional neuroimaging studies in addicted individuals have found that lower activation in executive function/inhibitory control areas during a cogni-tive task can serve as a predictor of drug relapse or treatment outcome. In the present study, we used functional neuroimaging during a decision-making task to predict weight gain in obese women. Participants completed a modified version of the DD task while a Siemens Allegra 3 Tesla magnet was used to acquire BOLD-based functional magnetic resonance imaging (fMRI) data. Each participant's body weight was measured at the fMRI session and in a subsequent lab session 1.3-2.9 years later. fMRI data were ana-lyzed with SPM5 software for executive function regions of interest (ROI) activated in previous fMRI studies of DD (inferior, middle and superior frontal gyri; anterior cingu-late cortex; inferior and superior parietal lobules); a whole brain analysis was also done. Confirming the results of previous fMRI studies, we found that more Hard vs. Easy trials on the DD task produced greater activation in executive function areas of the brain, and that more impulsive individuals had less activation on difficult trials than less impulsive individuals. Most significantly, decreased neural activation in executive function areas (inferior, middle, and superior frontal gyri; inferior parietal lobule) on Hard vs. Easy tri-als predicted a greater percent of weight gain/year. Our results suggest that impulsivity, a possible risk factor for obesity, may stem from hypoactivation of brain regions mediating executive function. Further research on differences in executive system activation as pre-dictors of weight gain could improve cognitive/behavioral therapies by focusing on ap-proaches that target potentially dysfunctional inhibitory control brain areas.

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