Differential cortical acetylcholine release in rats performing a sustained attention task versus behavioral control tasks that do not explicitly tax attention.

The present study used microdialysis techniques to compare acetylcholine release in the frontoparietal cortex of rats performing in a task requiring sustained attention with that of rats performing in two control procedures. The two control procedures were a fixed-interval 9-s schedule of reinforcement assessing primarily the effects of operant responding and comparable reward rates, and an operant procedure designed to test the effects of lever extension to prompt responding. These two control procedures involved comparable sensory-motor and motivational variables to those of the sustained attention task, but did not explicitly tax attentional processes. Performance of the sustained attention task was associated with a significant increase in cortical acetylcholine efflux, reaching a maximum of nearly 140%. Performance of the two control procedures was associated with significantly smaller (approximately 50%) increases in cortical acetylcholine release. This robust dissociation between attentional and control performance-associated increases in cortical acetylcholine release resulted, in part, from the elimination of the pre-task transfer of the animals into the operant chambers and the associated increases in acetylcholine release observed in previous studies. The present results support the hypothesis that demands on attentional performance, as opposed to the frequency of lever pressing, reward delivery and other task-related variables, selectively activate the basal forebrain corticopetal cholinergic system.