Dimensions of sucrose solutions in the successive negative contrast effect

Abstract

The consummatory successive negative contrast (cSNC) task typically involves administering food-deprived rats 10 daily 5-min sessions of access to 32 % sucrose (preshift) followed by a few sessions in which the concentration is reduced to 4 % sucrose (postshift). Such sucrose downshift leads to transient suppression of consummatory behavior. Reward downshifts were used to determine whether food-deprived rats treat sucrose solutions as food, because sweetness is a proxy for its caloric content, or as water, because a solution has hydration content. In Experiment 1, a cSNC effect was obtained in food-deprived animals, but not in water-deprived animals. This suggested that food deprivation focused attention on the feeding dimension of sucrose, whereas water deprivation focused attention on the drinking dimension of sucrose. Sucrose downshift results in a greater caloric change than in hydration content because both concentrations continue to provide fluid. Experiments 2 and 3 offered presession access to rewards either before preshift or before postshift sessions, respectively. Consistent with this attentional view, presession access to water (which should focus attention on the feeding dimension), but not to food (which should focus attention on the drinking dimension), suppressed consummatory behavior after a sucrose downshift. Presession access to food, like water deprivation, enhanced the hydration properties of the sucrose solution at the expense of its caloric properties. These results are consistent with an attentional hypothesis according to which the internal state, manipulated via deprivation or presession reward access, determines which dimension of the sucrose reward would control consummatory behavior.