Changes in extracellular levels of noradrenaline in rat prefrontal cortex during contingent and noncontingent performance of a five-choice serial reaction time task. Contingent animals (n = 10) and their yoked counterparts (n = 10) were run on the task over two consecutive daily sessions. The task was initiated after a 1 hr baseline collection period at a time of 0 min. The data are expressed as a percentage of the mean basal efflux (±SEM; n = 10).