['Both monkey and human studies have suggested that attentional orienting may be mediated by the cholinergic neurotransmitter system.', 'The purpose of the present study was to examine whether the cholinergic agonist (nicotine) and/or antagonist (scopolamine) influence covert orientation in the rat.', 'Rats carried out a visual reaction time task to measure covert orienting of attention following systemic administration of nicotine or scopolamine.', 'Nicotine reduced reaction times, abolishing the validity effect by differentially speeding the reaction times for invalidly cued targets. Conversely, scopolamine increased the validity effect by disproportionately lengthening reaction times to invalidly cued targets.'] Does cholinergic neurotransmission influence covert orientation of visuospatial attention in the rat?