Associative learning in animals

Caffeine is widely consumed almost everywhere, typically in flavored drinks. The pharmacological affects of the caffeine affect our reactions to those drinks, i.e., whether we like and want them. In a rat model of caffeine consumption we will examine the extent to which rats want/don't want and like/don't like novel flavors that (1) accompany the first use of caffeine; and (2) that accompany the resumption of caffeine intake when the rat is in caffeine withdrawal or (3) accompany the intake of a non-cafffeinated drink when the rat is in caffeine withdrawal. Examples of the questions we will ask include: (1) Will a rat come to want and like a flavor of a caffeinated beverage that he experienced while caffeine deprived and which alleviated withdrawal? Does the answer depend on whether the rat was caffeine deprived when we asked the question? Wanting will be inferred from the preference for the target flavor when it is pitted against a neutral flavor in a 2-bottle preference test. Liking will be inferred from the rats' orofacial responses to a flavor that is dripped into its mouth for a minute or two. Liked and disliked flavors are known to evoke markedly different patterns of behavior. Disliked (unpalatable) flavors elicit gapes, rubbing the chin against the floor and passing the forelimbs over the face and then flailing them, thereby throwing off droplets of the tastant. Liked (palatable) flavors are known to evoke rapid mouth movements and tongue protrusions. Changes in wanting are not always accompanied by changes in liking, e.g., preference for a flavor increases if it has been paired with sweet saccharin, but orofacial responses to that flavor do not change. Our goal is to understand the ways in which caffeine contributes to changes in liking and wanting flavors.