Multiple nicotinic receptors seem to exist in brain as revealed by neurophysiological, neurochemical, molecular and immunological studies. The mechanisms for their involvement in higher functions including learning and memory are still relatively unknown. The nicotinic receptor subtypes in human brain undergo changes during aging. Deficits of brain nicotinic receptors have been traced in neurodegenerative disorders as Alzheimer's disease and Parkinson's disease. Brain imaging studies in patients and neurochemical studies in autopsy brain tissue from Alzheimer patients reveal significant losses of the nicotinic receptors. New therapeutic compounds tried in Alzheimer's disease, aiming to increase cholinergic activity in the brain, act via the nicotinic receptors in brain. Augmentation of nicotinic receptor function in brain might be of importance for alleviating some of the cognitive impairments in Alzheimer's disease.