Event-Related Desynchronization (ERD) Correlated with Cognitive Activity

One characteristic feature of the human brain is its ability to generate rhythmic activity within the 7–13 Hz (alpha) and 15–20 Hz (beta) frequency band. These rhythmic activities can be found in intracerebral recordings (Cooper et al., 1965) and in electrocorticograms (Jasper and Penfield, 1949) and were first recorded in the electroencephalogram (EEG) from an intact skull by Berger in 1933. In addition to their sinusoidal behavior and characteristic frequency, alpha and beta band rhythms demonstrate another characteristic feature: the reactivity to exogenous and endogenous events. Well-known examples are the alpha blocking of occipital alpha rhythm after light stimulation (Berger, 1933) and the blocking of central mu rhythm during movement (Chatrian, 1976).