Aiming at a formulation of a cytokine model of cognitive function under immunologically unchallenged physiological conditions, this article reviews the cytokine biology in the central nervous system (CNS) and recent developments in normal cytokine functions within the CNS that subserve cognitive processes. Currently available evidence shows that the cytokines IL-1beta, IL-6 and TNF-alpha play a role in complex cognitive processes at the molecular level, such as synaptic plasticity, neurogenesis, as well as neuromodulation. Such findings provide evidence for a cytokine model of cognitive function, which shows that cytokines play an intimate role in the molecular and cellular mechanisms subserving learning, memory and cognition under physiological conditions. These cytokine-mediated cognitive processes have implications in the long-term development and pathogenesis of specific neuropsychiatric disorders such as major depression and dementia. The identification of this central role of cytokines in various brain activities during health provides greater insight into normal brain functions, especially synaptic plasticity, memory and cognition, and facilitates the understanding of specific biological mechanisms involved in neuropsychiatric diseases, such as dementia and depression. In order to extend the suggested cytokine model of cognitive function onto other members of the cytokine family, future research is required to investigate the physiological effects of other cytokines such as interferon-gamma (IFNgamma), alpha(1)-antichymotrypsin and IL-2 on cognitive function at the molecular level under immunologically unchallenged conditions.