The functional significance of absolute power with respect to event-related desynchronization

The question is examined whether the extent of changes in relative band pow er as measured by event-related desynchronization (ERD) depends on absolute band power. The results for target stimuli of a simple oddball task indica te that the prestimulus (reference) level of absolute band power has indeed a strong influence on ERD. Whereas for the alpha band large band power in the reference interval is related to a strong degree of alpha suppression a s measured by ERD, the opposite holds true for the theta band. Here, a low level of band power during the reference interval is related to a pronounce d increase in band power during the processing of the target stimulus. In c ontrast to alpha and theta, ERD in the delta band is not influenced by the magnitude of band power in the reference interval.