Setting the occasion for incentive motivation: implications for addiction

The context in which reward-paired cues are encountered sets the occasion for appropriate reward-seeking but may also spur inappropriate behaviors such as the renewal of drug-seeking. The psychological processes underlying occasion setting remain unclear as contexts are diffuse and difficult to isolate from other stimuli. To overcome this, we modeled a context as a phasic and discrete event - an occasion setter - which allowed for control over its presentation and influence on cue-driven reward-seeking. This allowed us to directly assess how occasion setters, like contexts, regulate the predictive and motivational significance of Pavlovian cues. Male rats (n=50) were trained in a Pavlovian paradigm where the presentation of an ambiguous conditioned stimulus was reinforced only if preceded by an occasion setting cue. We assessed the motivational value of the occasion setter and conditioned stimulus alone or in combination using conditioned reinforcement. Rats showed enhanced conditioned approach to the reward port during the reward-adjacent conditioned stimulus when it was preceded by the occasion setter. When allowed the opportunity, rats responded more to obtain presentations of the conditioned stimulus in combination with the occasion setter than the conditioned stimulus alone. Critically, rats also worked to obtain presentations of the occasion setter alone more than the conditioned stimulus, and this was resistant to manipulations of the value of the occasion setter. We conclude that occasion setting can act via incentive motivational mechanisms and that, apart from resolving predictive information about ambiguous reward-paired cues, occasion setters themselves generate states of appetitive motivation that can facilitate reward-seeking.