Abstract: Abstract: Changes in acetylcholine extracellular levels correlate the activity of the cholinergic nerve endings in the brain. Extracellular acetylcholine in both cortex and hippocampus is mainly originated from the afferent basal forebrain cholinergic neurons. Acetylcholine release is detected during cognitive processes in awake and free moving animals in vivo by ways of microdialysis technique, to investigate the relationship between brain acetylcholine release and specific cognitive activity. Activation of the forebrain cholinergic system and enhancement of acetylcholine release has been demonstrated in conditions in which the animals are required to analyze novel stimuli and during performance of learning and memory, spatial working memory, attention, motor activity and exploratory behavior. These results suggest that central cholinergic system activity be closely involved in cognitive procedure

Key words: acetylcholine, learning and memory, attention, locomotor activation, exploratory behavior