The overarching goal of this project is to test the hypothesis that impulsivity underlies pathological eating in obese participants with Binge Eating Disorder (BED). Our model proposes that binge eating is analogous to drug addiction, and impulsivity is an underlying factor in these addictive behaviors. Studies on patients with bulimia nervosa have reported greater impulsivity compared to normal controls, and there is an association between poor treatment response and high impulsivity in bulimics. There has been less work with BED and obese individuals;however, impulsivity might be expected to play a prominent role in excessive eating. This hypothesis is supported in a recent study indicating that women with BED show greater motor impulsivity on the Barratt Impulsivity Scale compared to those without BED (Nasser et al. 2004). In the proposed study, the cognitive and motor forms of impulsivity will be tested in participants with and without BED, using delay discounting (DD) and Go/No-go tasks, neurocognitive and personality tests, sweet-preference testing and magnetic resonance imaging (MRI) to test whether the impulsivity is associated with underlying neurobiological abnormalities in BED patients and controls. Magnetic resonance spectroscopy (MRS) will be used to measure brain GABA levels with BED, and diffusion tensor imaging (DTI) will be used to observe white matter abnormalities that have been found in cocaine abusing individuals. Imaging results will be related to personality, impulsivity, and neuropsychological data, thus investigating the neurobiological roots of impulsivity in BED. BED and control groups will also be tested for sweet-taste preference, as preference for sweets is predictive of impulsive behavior and various forms of drug abuse.
The specific aims for this project are: 1) To assess impulsivity in participants with BED compared to weight-matched controls by their performance on DD and Go/No-go tasks and to relate the results to personality instruments, neurocognitive measures, sweet preference, and imaging results. Comparisons will also be made to cocaine-using participants and controls in Project 2, 2) To assess white matter microstructure in participants with BED and controls using DTI measures, 3) to assess brain GABA in participants with BED and controls by employing MRS and correlating results with duration of illness as well as measures of impulsivity, personality and neurocognitive tests. Most of the proposed techniques have never been used in BED patients, and the findings will prove useful in understanding the relationship between BED, cocaine addiction, and impulsivity. These findings may aid in early screening of BED, prevention of obesity, and development of behavioral and pharmacological treatments for obese individuals.
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