Amanda S. Bruce

Neural Mechanisms Associated With Food Motivation in Obese and Healthy Weight Adults

One out of three adults in the United States is clinically obese. Excess food intake is associated with food motivation, which has been found to be higher in obese compared to healthy weight (HW) individuals. Little is known, however, regarding the neural mechanisms associated with food motivation in obese compared to HW adults. The current study used functional magnetic resonance imaging (fMRI) to examine changes in the hemodynamic response in obese and HW adults while they viewed food and nonfood images in premeal and postmeal states. During the premeal condition, obese participants showed increased activation, compared to HW participants, in anterior cingulate cortex (ACC) and medial prefrontal cortex (MPFC). Moreover, in the obese group, self‐report measures of disinhibition were negatively correlated with premeal ACC activations and self‐report measures of hunger were positively correlated with premeal MPFC activations. During the postmeal condition, obese participants also showed greater activation than HW participants in the MPFC. These results indicate that brain function associated with food motivation differs in obese and HW adults and may have implications for understanding brain mechanisms contributing to overeating and obesity, and variability in response to diet interventions.

Obese children show hyperactivation to food pictures in brain networks linked to motivation, reward and cognitive control.

Objective:To investigate the neural mechanisms of food motivation in children and adolescents, and examine brain activation differences between healthy weight (HW) and obese participants.Subjects:Ten HW children (ages 11–16; BMI < 85%ile) and 10 obese children (ages 10–17; BMI >95%ile) matched for age, gender and years of education.Measurements:Functional magnetic resonance imaging (fMRI) scans were conducted twice: when participants were hungry (pre-meal) and immediately after a standardized meal (post-meal). During the fMRI scans, the participants passively viewed blocked images of food, non-food (animals) and blurred baseline control.Results:Both groups of children showed brain activation to food images in the limbic and paralimbic regions (PFC/OFC). The obese group showed significantly greater activation to food pictures in the PFC (pre-meal) and OFC (post-meal) than the HW group. In addition, the obese group showed less post-meal reduction of activation (vs pre-meal) in the PFC, limbic and the reward-processing regions, including the nucleus accumbens.Conclusion:Limbic and paralimbic activation in high food motivation states was noted in both groups of participants. However, obese children were hyper-responsive to food stimuli as compared with HW children. In addition, unlike HW children, brain activations in response to food stimuli in obese children failed to diminish significantly after eating. This study provides initial evidence that obesity, even among children, is associated with abnormalities in neural networks involved in food motivation, and that the origins of neural circuitry dysfunction associated with obesity may begin early in life.

Brain Responses to Food Logos in Obese and Healthy Weight Children

OBJECTIVE To evaluate brain activation in response to common food and nonfood logos in healthy weight and obese children. STUDY DESIGN Ten healthy weight children (mean body mass index in the 50th percentile) and 10 obese children (mean body mass index in the 97.9th percentile) completed self-report measures of self-control. They then underwent functional magnetic resonance imaging while viewing food and nonfood logos. RESULTS Compared with the healthy weight children, obese children showed significantly less brain activation to food logos in the bilateral middle/inferior prefrontal cortex, an area involved in cognitive control. CONCLUSION When shown food logos, obese children showed significantly less brain activation than the healthy weight children in regions associated with cognitive control. This provides initial neuroimaging evidence that obese children may be more vulnerable to the effects of food advertising.

Robust relation between temporal discounting rates and body mass

When given the choice between

Importance of reward and prefrontal circuitry in hunger and satiety: Prader-Willi syndrome vs simple obesity.

100 today and

Changes in brain activation to food pictures after adjustable gastric banding

110 in 1 week, certain people are more likely to choose the immediate, yet smaller reward. The present study examined the relations between temporal discounting rate and body mass while accounting for important demographic variables, depressive symptoms, and behavioral inhibition and approach. After having their heights and weights measured, 100 healthy adults completed the Monetary Choice Questionnaire, the Beck Depression Inventory-II, and the Behavioral Inhibition Scale/Behavioral Approach Scale. Overweight and obese participants exhibited higher temporal discounting rates than underweight and healthy weight participants. Temporal discounting rates decreased as the magnitude of the delayed reward increased, even when other variables known to impact temporal discounting rate (i.e., age, education level, and annual household income) were used as covariates. A higher body mass was strongly related to choosing a more immediate monetary reward. Additional research is needed to determine whether consideration-of-future-consequences interventions, or perhaps cognitive control interventions, could be effective in obesity intervention or prevention programs.

Branding and a child’s brain: an fMRI study of neural responses to logos

Background:The majority of research on obesity (OB) has focused primarily on clinical features (eating behavior, adiposity measures) or peripheral appetite-regulatory peptides (leptin, ghrelin). However, recent functional neuroimaging studies have demonstrated that some reward circuitry regions that are associated with appetite-regulatory hormones are also involved in the development and maintenance of OB. Prader–Willi syndrome (PWS), characterized by hyperphagia and hyperghrelinemia reflecting multi-system dysfunction in inhibitory and satiety mechanisms, serves as an extreme model of genetic OB. Simple (non-PWS) OB represents an OB-control state.Objective:This study investigated subcortical food motivation circuitry and prefrontal inhibitory circuitry functioning in response to food stimuli before and after eating in individuals with PWS compared with OB. We hypothesized that groups would differ in limbic regions (that is, hypothalamus, amygdala) and prefrontal regions associated with cognitive control (that is, dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex (OFC) after eating.Design and participants:A total of 14 individuals with PWS, 14 BMI- and age-matched individuals with OB, and 15 age-matched healthy-weight controls viewed food and non-food images while undergoing functional MRI before (pre-meal) and after (post-meal) eating. Using SPM8, group contrasts were tested for hypothesized regions: hypothalamus, nucleus accumbens (NAc), amygdala, hippocampus, OFC, medial PFC and DLPFC.Results:Compared with OB and HWC, PWS demonstrated higher activity in reward/limbic regions (NAc, amygdala) and lower activity in the hypothalamus and hippocampus in response to food (vs non-food) images pre-meal. Post meal, PWS exhibited higher subcortical activation (hypothalamus, amygdala, hippocampus) compared with OB and HWC. OB showed significantly higher activity versus PWS and HWC in cortical regions (DLPFC, OFC) associated with inhibitory control.Conclusion:In PWS, compared with OB per se, results suggest hyperactivations in subcortical reward circuitry and hypoactivations in cortical inhibitory regions after eating, which provides evidence of neural substrates associated with variable abnormal food motivation phenotypes in PWS and simple OB.

Mild visual acuity disturbances are associated with performance on tests of complex visual attention in MS

BACKGROUND Adjustable gastric banding is an effective weight-loss treatment, but little is known about the neural mechanisms underlying weight loss. The purpose of the present study was to determine whether gastric banding affects brain function in regions previously implicated in food motivation, reward, and cognitive control. The setting for the study was the University of Missouri-Kansas City, Department of Psychology; Hoglund Brain Imaging Center, University of Kansas Medical Center; and private practice in the United States. METHODS Ten obese participants were recruited before adjustable gastric banding surgery (mean body mass index before surgery 40.6 ± 1.96 kg/m2). Their mean body mass index at 12 weeks after surgery was 36.1 ± 2.32 kg/m2, with a mean percentage of excess weight loss of 25.21% ± 8.41%. Functional magnetic resonance imaging scans were conducted before and 12 weeks after adjustable gastric banding surgery. At each assessment point, the participants completed questionnaires assessing food motivation and were scanned while hungry (before eating) and immediately after a standardized meal (after eating). During the functional magnetic resonance imaging scans, the participants viewed food pictures, nonfood pictures (animals), and blurred baseline control pictures. The functional magnetic resonance imaging data were analyzed using BrainVoyager QX. RESULTS After surgery, the participants reported significantly less food motivation and more cognitive restraint. The participants also showed decreased brain activation to food versus nonfood pictures in regions implicated in food motivation and reward, including the parahippocampus, medial prefrontal cortex, insula, and inferior frontal gyrus. In contrast, they demonstrated increased activation to food versus nonfood pictures in anterior prefrontal cortex, a region implicated in cognitive control and inhibition. CONCLUSION This is the first study to examine the functional brain changes after gastric banding surgery and 1 of the first studies to longitudinally examine neural changes associated with weight loss. These results have provided preliminary evidence that adjustable gastric banding alters brain function in regions known to regulate reward and cognitive control.

A comparison of functional brain changes associated with surgical versus behavioral weight loss

Branding and advertising have a powerful effect on both familiarity and preference for products, yet no neuroimaging studies have examined neural response to logos in children. Food advertising is particularly pervasive and effective in manipulating choices in children. The purpose of this study was to examine how healthy children’s brains respond to common food and other logos. A pilot validation study was first conducted with 32 children to select the most culturally familiar logos, and to match food and non-food logos on valence and intensity. A new sample of 17 healthy weight children were then scanned using functional magnetic resonance imaging. Food logos compared to baseline were associated with increased activation in orbitofrontal cortex and inferior prefrontal cortex. Compared to non-food logos, food logos elicited increased activation in posterior cingulate cortex. Results confirmed that food logos activate some brain regions in children known to be associated with motivation. This marks the first study in children to examine brain responses to culturally familiar logos. Considering the pervasiveness of advertising, research should further investigate how children respond at the neural level to marketing.

Moving from tube to oral feeding in medically fragile nonverbal toddlers.

Because MS patients frequently report visual acuity disturbances, neuropsychologists often screen patients for severe visual acuity disturbances and tailor test batteries that minimize the need for intact vision. Less is known about how mild visual acuity disturbances may influence neuropsychological test performance. This study examined the extent to which mild visual acuity disturbances influence performance on visually-based tests of complex attention. Relapsing-remitting and secondary progressive MS patients who reported adequate vision were recruited for this study. A battery was administered that included the oral version of the Symbol Digit Modalities Test (SDMT), the Visual Elevator (VE) subtest from the Test of Everyday Attention, and a reduced near vision eye chart. Results suggested that, in addition to measuring higher order cognitive processes, visual tests of attention are sensitive to mild primary visual disturbances in MS.