Dissociation of reinforcement and motivational processes in an operant runway model of goal-directed behavior

Environmental and contextual cues exert a profound influence on behavior. Such cues are said to have incentive or motivational properties because they elicit behavior that increases the probability of interaction with appetitive stimuli (e.g., food) or decreases the probability of interaction with aversive ones (e.g., a predator). This conception of behavior suggests that motivation is the process responsible for activating and directing behavior toward a to-be-obtained goal. The problem inherent in this notion arises from the difficulty separating those processes that precede and motivate behavior from those that are a consequence of interaction with the goal object. For this reason, the present dissertation is an attempt to dissociate motivational from reinforcement processes in the production of goal-directed behavior. Toward this end it begins with a brief discussion of the concept of motivation in an attempt to delineate the motivational and reinforcement realms, and then presents the results of three sets of experiments that use an operant runway procedure in an investigation of the neural substrates of motivation versus reinforcement. The first set of experiments demonstrates the ability of environmental discriminative cues to activate and direct behavior (i.e., to reliably elicit a motivated state). The second set reveals a behavioral and neurochemical dissociation between reinforcement and motivation, while the third set provides the first reliable model of cue-induced relapse to extinguished drug-seeking behavior. Taken together, these experiments suggest that (1) discriminative stimuli reliably elicit goal-directed behavior; (2) motivation and reinforcement are distinct, albeit interactive, processes with separable behavioral effects; and (3) the same dopamine receptor antagonist treatments that reliably block both food and drug reinforcement leave the motivation to seek these substances intact.