Cognitive ontologies help in understanding brain functions, but they are also important because of the intensifying search for the means to optimize interaction in human-computer systems with consideration of psychological and neurophysiological characteristics of the users. Based on tomographic datasets, cognitive atlas is being developed, as the foundation for studying regularities in cognitive processes. However, for the analysis of fast activities in the brain or for development of brain-computer interfaces, electroencephalographic data registration is more appropriate. So, in our paper we provide definition of the cognitive reserves and describe approaches towards the corresponding ontology development, using attributes of the brain electric activity. We demonstrate that every mental function can be represented as super-position of neural oscillations due to interaction of specific brain structures. Analyzing the data presented in the existing literature, we extract the data that correspond to the organizational centers of attention and memory systems, or to the components of intelligence that represent cognitive reserves during the brain aging. We further describe functionality of low- and high-frequency oscillations. The assessment of their relationship and spatial correspondence is seen as a promising direction for determining the reserves of the brain functions.