Frontal-parietal responses to "oddball" stimuli depicting "fattened" faces are increased in successful dieters: an electroencephalographic study.

Here we tested the hypothesis that compared with normal weight non dieting (control) subjects, normal weight successful dieters submitted to a rigorous and continuous monitoring of body weight (i.e. karate athletes) are characterized by an increase of cortical responses to oddball visual stimuli depicting the enlargement of faces or foods, as neural underpinning of attention processes related to the control of weight and eating. Electroencephalographic (EEG) data were recorded in 18 successful dieters (5 females) and 24 non dieting subjects (9 females). The subjects were given frequent (70%) and rare (30%) stimuli depicting faces (FACE), food (FOOD), and landscapes (CONTROL). The task was to click the mouse after the rare stimuli. The rare stimuli depicted the frequent stimuli graphically dilated by 25% along the horizontal axis. Cortical responses accompanying attention processes were probed by the difference between positive event-related potentials peaking around 400-500ms post-stimulus for the rare minus frequent stimuli (P300). The popular freeware LORETA estimated P300 cortical sources. The results showed that in the FACE condition, the amplitude of left frontal (BA 6) and medial parietal (BA 5) P300 sources was higher in the successful dieters (karate athletes) than non dieting subjects. These results disclose that frontal-parietal responses to "oddball" stimuli depicting enlarged faces (i.e. representing face fattening) are enhanced in successful dieters (karate athletes). Future studies should evaluate this effect in other populations of successful dieters (i.e. boxers, top models etc.).