An Increase in Post-Reinforcer ‘Preference Pulses’ Underlies an MDMAInduced Increase in Reinforcer Sensitivity Following Acute but Not Chronic Exposure

Both acute and chronic exposure to 3, 4-methylenedioxymethamphetamine (MDMA) is associated with impairments in a range of conditional discrimination tasks that reflect memory function, decision making and self-control [1-3]. However, the mechanism by which MDMA decreases performance in these tasks is not clear. One interpretation of such findings has been that overall stimulus control is impaired (i.e., rats have trouble discriminating between response options and/or which reinforcers were associated with which stimulus-response option). This might underlie the observed overall drop in discrimination across all delays in DMTS tasks. Should this be the case then it would be expected that rats would also display a reduced molar sensitivity to overall reinforcer ratios arranged across concurrently available response alternatives.