Impulsivity and Time Perception

Cannabis smokers having begun prematurely their consumption (before 16 years) present a persistent impulsivity much later after have stopped their consumptions. The literature highlights that the impulsivity promotes the passage towards a compulsive consumption, and the loss of control. To explain this phenomenon, some authors hypothesized that impulsivity would lead the subjects to overestimate the duration of events and to choose immediate rewards than preferred but delayed rewards. This hypothesis questions the role of the temporal anticipation in the impulsive choices. In a first hypothesis, the temporal impulsivity could be an endogenous deficit bound to the reward, and would be responsible for disorders of the temporal anticipation. In this case, the disorders should be observed especially when the subject anticipates a reward. Alternately, a disorder of the temporal anticipation could provoke impulsivity, and in this case, would be present with or without reward. To separate these hypotheses, we propose to test the capacities of temporal anticipation of non-smokers and early smokers of cannabis by means of a behavioral task " Hazard function task ", which allow to measure the capacity of a subject to anticipate the apparition of an event on the basis of a temporal cue. The neuronal correlates will be measured by a recording EEG of the wave ' CNV ' (fix a quota for denial of variation) which reflects the temporal accumulation and the processes of anticipation.