ABSTRACT
The diagnostic concept of age-associated memory impairment (AAMI) suggests that clinically recognized memory dysfunction could be a feature of normal aging. Although the memory impairment associated with aging is well recognized, underlying neurobiological mechanisms of cognitive decline remain unclear. There are a number of age-related structural and physiological changes in the brain that could have implications for cognitive decline in the elderly. The impact of these age-related changes in the brain on cognition has been studied using postmortem neurochemical, neuropathological findings or neuroimaging techniques. The available evidence from studies in aged and demented humans suggested that cognitive deficits related to aging might involve concomitant alterations of various neurochemical systems in several brain regions such as the striatum, the hippocampus or the cortex. It also seems that these alterations occur in a complex way which affects dopaminergic, glutamaterigc and serotonergic neurotnasmission in addition to the loss of cholinergic neurons in the basal forebrain, However, data collected to explain the mechanism of AAMI are still limited, the definite interpretation of these findings must await futher studies.