Cholinergic neurotransmission influences covert orientation of visuospatial attention in the rat

Rationale: Both monkey and human studies have suggested that attentional or ienting may be mediated by the cholinergic neurotransmitter system. Objecti ves: The purpose of the present study was to examine whether the cholinergi c agonist (nicotine) and/or antagonist (scopolamine) influence covert orien tation in the rat. Methods: Rats carried out a visual reaction time task to measure covert orienting of attention following systemic administration of nicotine or scopolamine. Results: Nicotine reduced reaction times, abolish ing the validity effect by differentially speeding the reaction times for i nvalidly cued targets. Conversely, scopolamine increased the validity effec t by disproportionately lengthening reaction times to invalidly cued target s. Conclusions: Taken together, these data indicate that cholinergic transm ission represents an important neurochemical substrate of visuospatial atte ntion, specifically influencing disengagement or movement of attention.