Cognition deficits have receivedmuch attention over the last two decades. The severe impairment of cholinergic function in dementias, particularly in age-related cognitive decline andAlzheimer’s disease has been indicated. However, loss of cholinergic activity may play a key role in the cognitive symptoms but it cannot clearly demonstrate the entire mechanism involved. Increase in acetylcholine or administration of direct cholinergic agonists are not able to combat such cognitive impairments. Moreover, stimulation of monoaminergic activity, in conjunction with cholinergic therapies, may induce effective treatment ofAlzheimer’s disease [1]. Furthermore, effects of other neurotransmitters, such as cathecholamines, serotonin, GABA, histamine, adenosine, nitric oxide and cholecystokinin and their role in learning and memory in animals have been tested. Decrease or increase in levels of the neurotransmitters or activation or blockade of different receptors related to the neurotransmitters indicate that other mechanismsmay alter learning andmemory. The role of a network consisting of different neurotransmitter systems may be important for learning and memory processing. Therefore, the aim of this section is to simply show the involvement of different neurotransmitter systems in cognitive behavior.