Individual Differences in Reward and Somatosensory-Motor Brain Regions Correlate with Adiposity in Adolescents

Abstract

The prevalence of adolescent obesity has increased dramatically over the past three decades, and research has documented that the number of television shows viewed during childhood is associated with greater risk for obesity. In particular, considerable evidence suggests that exposure to food marketing promotes eating habits that contribute to obesity. The present study examines neural responses to dynamic food commercials in overweight and healthy-weight adolescents using functional magnetic resonance imaging (fMRI). Compared with non-food commercials, food commercials more strongly engaged regions involved in attention and saliency detection (occipital lobe, precuneus, superior temporal gyri, and right insula) and in processing rewards [left and right nucleus accumbens (NAcc) and left orbitofrontal cortex (OFC)]. Activity in the left OFC and right insula further correlated with subjects' percent body fat at the time of the scan. Interestingly, this reward-related activity to food commercials was accompanied by the additional recruitment of mouth-specific somatosensory-motor cortices-a finding that suggests the intriguing possibility that higher-adiposity adolescents mentally simulate eating behaviors and offers a potential neural mechanism for the formation and reinforcement of unhealthy eating habits that may hamper an individual's ability lose weight later in life.

Keywords: action observation; advertising; fMRI; food; obesity.

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Figures

Figure 1.

Study design. Subjects viewed episode of The Big Bang Theory with food and control (non-food) commercials embedded throughout as typical commercial breaks.

Figure 2.

Brain regions showing greater activity when viewing FOOD commercials than NON-FOOD commercials. Activations (P < 0.005, 173 contiguous voxels) are displayed on an inflated rendering of the cortical surface (Marcus et al. 2010; Marcus et al. 2011). Greater activation for FOOD commercials was observed in a number of occipital regions (A) extending from the occipital pole through the fusiform gyrus, the left superior and middle temporal gyrus (B), the precuneus (C and D), and the left orbital frontal cortex (E).

Figure 3.

Regions correlating with percent body fat. (A) The magnitude of response to food commercials in a region of the left orbitofrontal cortex, defined by the FOOD > NON-FOOD contrast, correlated with percent body fat (r = 0.43, P < 0.01) and BMI (r = 0.38, P < 0.05). (B) The magnitude of response to food commercials in a region of the right insula, defined by the FOOD > NON-FOOD contrast, correlated with percent body fat (r = 0.38, P < 0.05) and BMI (r = 0.41, P < 0.05).

Figure 4.

Whole-brain response to FOOD commercials covaried with percent body fat, accounting for age and gender. Activations are overlayed on an inflated representation of the cortical surface (Marcus et al. 2010; Marcus et al. 2011). Activations were observed in bilateral regions of sensorimotor cortices along the pre- and post-central gyri and bilateral central sulci and a region of the right insula/posterior opercula.

Figure 5.

(A) Functionally defined sensorimotor networks via resting-state connectivity (Power et al. 2011) provide evidence for separable mouth and hand (body) subnetworks. (B) Activity from (A) overlaid on network boundaries from Power et al. (2011) demonstrates specificity of activity to “mouth” sensorimotor network.