Double Blind Randomized, Monocentric, Cross-over, Placebo-controlled Study to Evaluate the Effect of Morphine and Naloxone on Motivation (MBBAnalgesic) (MBBAnalgesic)

The aim of the current study is to examine the role of the opioïd system on the cognitive parameters of motivation. They are embedded in a conceptual framework of motivation that merges decision-making and reinforcement learning theories. Every action is conceived as path from one state to another. The different states are associated to different values (positive for rewards and negative for punishments), and the different actions to different costs (risk, effort and delay). The tasks are designed such that the sensitivity to the state and action parameters can be inferred by fitting computational models.The primary objective is to characterize the effect of Morphine 0,05mg/kg and Naloxone 10mg on cost accumulation slope, assessed in an effort management task, in which participants are asked to squeeze a hand grip during 30 seconds at varying level of effort in order to win monetary payoff. Secondary objectives are to characterize the effect of Morphine 0,05mg/kg and Naloxone 10mg on other cognitive parameters of motivation (assessed with a motivational battery that includes rating, choice and learning tasks).