Functional brain imaging based on ERD/ERS

Sensory, cognitive and motor processing can result in changes of the ongoin g EEG in form of an event-related desynchronization (ERD) or event-related synchronization (ERS). Both phenomena are time-locked but not phase-locked to the event and they are highly frequency-band specific. The ERD is interp reted as a correlate of an activated cortical area with increased excitabil ity and the ERS in the alpha and lower beta bands can be interpreted, at le ast under certain circumstances, as a correlate of a deactivated cortical a rea. Spatial mapping of ERD/ERS can be used to study the dynamics of cortic al activation patterns. Examples from a movement task are reported. (C) 200 1 Elsevier Science Ltd. All rights reserved.