A time course analysis of satiety-induced instrumental outcome devaluation.

Abstract

Sensory-specific satiety is commonly used in studies of decision making to selectively devalue a food reward. Devaluation is reflected in an immediate reduction in the subsequent intake of the food and in the performance of actions that gain access to that food. Despite its frequent use, the lasting effects of satiety-induced devaluation on instrumental actions are unknown. Here, we examined the time course and contextual dependency of sensory-specific satiety-induced devaluation on instrumental responding and consumption. Rats were trained to perform two instrumental actions for two distinct food rewards. Then, one of the instrumental outcomes was provided ad libitum for 1hour in separate feeding cages and the effect of this devaluation was assessed 0, 2, or 5hours after satiation. At a delay of 0 or 2hours, both intake and instrumental responding were sensitive to the satiety treatment. That is, rats consumed less of the devalued outcome and responded less for the devalued outcome than for the valued outcome. By contrast, after 5hours, rats showed sensitivity to devaluation in consumption but not in instrumental responding. Strikingly, sensitivity to devaluation was restored for the instrumental response after a 5hour delay when devaluation was performed in the instrumental context. These results indicate that, in rats, specific satiety-induced devaluation endures and is context-independent for up to 2hours post-satiation. At longer delays, the impact of sensory-specific satiety on instrumental responding is context-dependent, suggesting that contextual cues may be required for the value of specific outcomes to control instrumental responding.