Methoden der Quellenanalyse spontaner und evozierter Hirnstromaktivität

Abstract

Two categories of models are available for the functional imaging of non-invasively recorded electric brain activity: instantaneous, or single-time-point methods and spatio-temporal modelling. Instantaneous models rely merely on the few voltage differences measured in a limited number of EEG channels at one sampling point. Therefore they require additional assumptions that rarely conform with the underlying physiology. In contrast, spatio-temporal models analyze all available information in the data at once. They create a spatial image of discrete multiple sources and a temporal image of source current waveforms reflecting the time course of circumscribed brain activities at a macroscopic level. The spatial image is limited in accuracy because of the low spatial sampling and noise in the data. It also depends on the correct choice of model. However, this can be validated by the new „regional source imaging” technique which scans the brain for active and inactive regions at a discrete voxel level. Source analyses are presented for averaged epileptic spikes and movement-related potentials. The „brain source images” revealed different excitation patterns in the active brain areas which conformed with the underlying physiology.