Attentional, hedonic and interoceptive correlates of implicit processes in addiction: a learning perspective

Addiction is characterised by maladaptive drug-approach behaviours, some of which may take place without conscious cognitive control. Through repeated associations with a substance, drug related stimuli acquire incentive salience properties via Pavlovian reward learning, triggering these responses. In order to better understand implicit processes in addiction it is crucial to increase our knowledge about unconscious reward mechanisms. Previous literature has failed to thoroughly demonstrate the ability of Pavlovian conditioned stimuli to generate responses in the absence of stimulus-outcome contingency awareness. Therefore, an effort was put to develop novel techniques measuring different aspects of conditioning. Using an Emotional Attentional Blink, we proved stimuli associated with high probabilities of reward (HR) generated increased attentional responses in participants Unaware of contingencies. Integrating Conditioned Stimuli (CS) as task-irrelevant distractors in a Flanker task we found HR stimuli interfered with cognitive control, again implicitly. A novel methodology, based on Bayesian analyses, allowed us determining the unconscious nature of learning, strengthening our findings. Conversely, subjective hedonic responses were not modulated by implicit learning, highlighting the inadequacy of such measures for the study of implicit conditioning. In order to further understand individual differences in the development of conditioned responses, we examined the role of interoception, the mental representation of internal bodily sensations, in this matter. It was shown that interoceptive awareness modulates the development of reward prediction and hedonic responses in Pavlovian conditioning. We also examined the effect of a natural reward, alcohol, on interoceptive awareness, and found that under acute alcohol administration interoceptive awareness facilitates the perception of subjective substance effects. These findings have important implications for our understanding of basic addictive processes. The ability of implicit CS to generate responses supports the existence of drug-approach behaviours devoid of conscious awareness. The role of interoception in Pavlovian conditioning provides the basis for its integration in classic learning theories.