Cortical generators of normal electroencephalographic waveforms: A literature review

Abstract

Introduction: EEG is a useful, noninvasive, safe technique to study the electrical activity of brain in various physiological and pathological conditions like alertness, sleep, seizure activity. Normal brain rhythms, the electroencephalogram (EEG) represents the electrical activity of brain as recorded through the metal electrodes applied over scalp. An insight to the possible source of EEG, various rhythms and its activation during certain maneuvers can give a better understanding to its applications. Materials and Methods: Number of electronic database, as well as library resources were searched for related references included in published literature till 2017, using following key words ‘cortical’, ‘electroenchephalogram’,’ EEG’,’ EEG Rhythm’,’ EEG wave’, ‘alpha wave’,’ beta wave’,’ theta wave’,’ delta wave’. Those which were related to our subject were included in the review. Results: Of the total number of studies we have finally included 35 studies from search results. These are mentioned in the references. Conclusion: Beta, Alpha, Theta & Delta are produced from various regions of the brain, including cortical & thalamic networks, hippocampus, reticular networks and so on. The rhythm of EEG can be correlated with the level of activation of the brain, with beta wave being produced during alert state and delta wave being produced during deep sleep. Interventions like hyperventilation and photic stimulation can be used to increase the diagnostic yield of EEG. It has been seen that sex-related differences do exist in the degree of lateralization of hemispheric function. Keywords: Electroencephalogram, Brain waves, Cortex, Thalamus, EEG.