The article reviews the literature on the diagnosis and treatment of cognitive impairment in the aspect of activity of main functional systems involved in functioning of the higher mental functions, cortical/subcortical interactions, afferent activating pattern of the reticular system and the cerebral blood flow system. The role of the latter is considered in frames of the concept of the neurovascular unit. Main points of application of drugs used for treatment of cognitive functions, including those which exert an effect on the capillary blood flow, are defined.