The valence of food in pictures and on the plate: impacts on brain and body

Food and food-related stimuli can be powerful elicitors of affect. Here we investigated how the valence of food pictures and the consummation of meals with different arrangements on the plate modulate physiological and subjective variables. In particular, we presented pictures of food stimuli rated as high or average in terms of valence, before and after participants consumed strictly standardized meals. The meals consisted either of several separate constituents on the plate (complex meal), or of exactly the same constituents mixed together (simple meal). Food pictures of positive or neutral valence had to be discriminated from randomly intermixed pictures of faces showing either happy or neutral expressions. During the complex meal, blood glucose increased more slowly than during the simple meal, indicating a beneficial effect of the former, worthy of further investigation because more rapid changes in glucose level are considered to be related to more intense food craving. For the food stimuli emotion effects were present both very early on and in the late positive complex. Hence, food pictures may elicit a rapid reflex-like affective response followed by a later evaluative stage. Interestingly, the valence-related ERP responses to food pictures seemed to be relative independent from motivational states, that is, satiation because the intervening meals did not modulate them.