Frontal attentional responses to food size are abnormal in obese subjects: an electroencephalographic study

OBJECTIVE: Are obese subjects characterized by a reduction of attentional cortical responses to the enlargement of food or body images? METHODS: Electroencephalographic data were recorded in 19 obese and 15 normal-weight adults during an "oddball" paradigm. The subjects were given frequent (70%) and rare (30%) stimuli depicting faces (FACE), food (FOOD), and landscapes (CONTROL), and clicked the mouse after the rare stimuli. These stimuli depicted the same frequent stimuli graphically dilated by 25% along the horizontal axis. Bioelectrical impedance indexed subjects' body fat percentage. Cortical attentional responses were probed by the difference between positive event-related potentials peaking around 400-500ms post-stimulus for the rare minus frequent stimuli (P300). Low resolution electromagnetic source tomography (LORETA) estimated P300 sources. RESULTS: In the FOOD condition, the amplitude of medial prefrontal P300 sources (Brodmann area 9) was lower in the obese than normal-weight subjects, and there was a negative correlation between the body fat percentage and the amplitude of these sources in all subjects as a single group. CONCLUSIONS: These results disclose that prefrontal attentional processes to food size are abnormal in obese subjects. SIGNIFICANCE: The present study motivates future research evaluating the effects of cognitive rehabilitation in obese subjects