Recently, numerous newel methods have flourished in brain research and cognitive sciences, increasing our knowledge of the ways in which the human brain processes information. Experimental studies utilizing modem neurophysiological and neuroimaging techniques (EEG; electroencephalogram, MEG; magneto encephalogram; fMRI; functional magnetic resonance imaging, PET; positron emission tomography) in association with cognitive processing have provided an opportunity to approach subtle brain-behavior relationships in a more direct and empirical manner than ever before. Although being one of the oldest psychophysiological methods to study brain activity, the electroencephalogram (EEG) can successfully be utilized in modem brain research in order to assess brain activity during cognitive functioning. In this chapter, the role of brain electric oscillations in revealing the neural basis of human cognitive and memory processes will be discussed.