Abstract
INTRODUCTION: Neuroimaging studies suggest that obese people might show hyperactivity of brain areas regarding reward processing, and hypoactivity of brain areas concerning cognitive control, when exposed to food cues. Although the effects of bariatric surgery on the central nervous system and eating behavior are well known, few studies have used neuroimage techniques with the aim of investigating the central effects of bariatric surgery in humans. OBJECTIVES: This paper systematically and critically reviews studies using functional neuroimaging to investigate changes on the patterns of activation of central areas related to the regulation of eating behavior after bariatric surgery. METHOD: A search on the databases Medline, Web of Science, Lilacs and Science Direct on Line, was conducted in February 2013, using the keywords "Neuroimaging", "Positron-Emission Tomography", "Magnetic Resonance Imaging", "Gastric Bypass", "Gastroplasty", "Jejunoileal Bypass", "Bariatric Surgery". RESULTS: Seven manuscripts were included; the great majority studied the central effects of Roux en Y gastric bypass, using positron emission tomography or functional magnetic resonance. CONCLUSIONS: Bariatric surgery might normalize the activity of central areas concerned with reward and incentive salience processing, as the nucleus accumbens and mesencephalic tegmental ventral area, as well as circuitries processing behavioral inhibition, as the dorsolateral prefrontal cortex.
Highlights
Neuroimaging studies suggest that obese people might show hyperactivity of brain areas regarding reward processing, and hypoactivity of brain areas concerning cognitive control, when exposed to food cues
positron emission tomography (PET) based papers studied the expression of dopamine receptors before and after bariatric surgery[8,13] and the activation of diverse brain regions in operated and nonoperated obese individuals and lean subjects, in fasting and after feeding states[11]
Dunn et al.[13] and Steele et al.[8] have conflicting findings, since the former documented reduced expression of dopamine receptors in areas associated with homeostatic and hedonic feeding behavior and the latter documented an increased expression of such receptors in areas associated with hedonic feeding
Summary
Neuroimaging studies suggest that obese people might show hyperactivity of brain areas regarding reward processing, and hypoactivity of brain areas concerning cognitive control, when exposed to food cues. Objectives: This paper systematically and critically reviews studies using functional neuroimaging to investigate changes on the patterns of activation of central areas related to the regulation of eating behavior after bariatric surgery. Conclusions: Bariatric surgery might normalize the activity of central areas concerned with reward and incentive salience processing, as the nucleus accumbens and mesencephalic tegmental ventral area, as well as circuitries processing behavioral inhibition, as the dorsolateral prefrontal cortex. Subcortical regions that process the reward associated with food, such as the mesencephalic ventral tegmental area (VTA) and the nucleus accumbens (NAC), have a key role in the configuration of complex cognitive mechanisms causing craving and search for food from environmental cues[2]. The subjective experiences of pleasure while eating unpalatable food when one is hungry, as well as the cravings for high-calorie foods in satiated individuals, stand for evidences of such interconnections[1]
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