Graphical display and statistical evaluation of event-related desynchronization (ERD).

A new method which enables quantification of event-related desynchronization (ERD) by measuring changes in the power of rhythmic activity within the alpha band during sensory stimulation and during the interstimulus interval of a CNV paradigm is described. For the processing, EEG trials recorded under the same stimulus conditions and with eyes closed are used. For the power changes, the statistical significance is tested with a non-parametric test. With the proposed method it is possible to measure very brief power changes of the order of 21 percent (corresponding to amplitude changes of 11%). An ERD may thus be observed in a restricted cortical region.