Motivational properties of smoking-associated stimuli modulated by their temporal position within the smoking ritual: behavioral, psychophysiological and neuroimaging evidence for their role as context stimuli

Abstract:

Tobacco addiction is characterized by excessive craving, loss of control over drug-intake and high rates of relapse, resulting from conditioned stimuli (CSs) formed by the association of previously neutral stimuli with smoke-intake. The effect of these stimuli, termed cue reactivity, is generally assumed to be a feature of smoking-associated stimuli, reflecting the incentive properties of smoking CSs. Therefore, we were interested in smoking stimuli from the terminal stage of the smoking ritual (END stimuli), since they are ideally suited to support conditioning with smoking but in contrast to normal smoking cues, which are typically preparatory (BEGIN stimuli), elicit only weak cue reactivity. In this project, we replicated the basic observation that terminal stimuli have poor cue reactivity and addressed the mechanisms of the terminal stimuli in a variety of ways.

Specifically, we showed that END stimuli fail to evoke the attention capturing effect seen for BEGIN stimuli. END stimuli do not elicit a strong incentive motivational state as indicated by affect-modulated startle. Moreover, END stimuli may evoke a different neural response pattern with activations as well as deactivations in the “addiction network”. Both stimuli can be dissociated by manipulations enhancing or decreasing the perceived availability of smoking. Interestingly, a reduction of smoke availability primarily attenuated the reactivity to BEGIN stimuli. Importantly, the reactivity evoked by END stimuli was only partially increased when presented simultaneously with an additional smoking cue in an effort to enhance smoke availability. Moreover, compared to BEGIN stimuli the experimental association of END stimuli with smoke reinforcement failed to condition preparatory skin conductance and corrugator responses. These differences in the predictive relationship to smoke intake and the differential sensitivity of both stimuli to manipulations of smoke availability and smoke reinforcement may provide a further link to putative inhibitory functions of terminal stimuli.

It may be concluded that terminal stimuli are not inert or weak cues, but may be formed by association with smoking. Their reactivity is different from and maybe even opposite to normal cues, possibly embodying information about the availability of smoke. The pattern of effects suggest putative modulatory influences of this information, which within the smoking ritual could be tentatively seen as a signal for reducing excitatory activity associated with the initiation and implementation of smoke intake. The pattern of effects suggests that the temporal position of the smoking ritual encodes contextual stimuli important for understanding incentive effects of smoking.