Assessing the accuracy of topographic EEG mapping for determining local brain function

Objective: There has been considerable discussion regarding the accuracy of topographic electroencephalographic (EEG) maps for assessing local cerebral function. We performed this study to test the accuracy of EEG mapping by examining the association between electrical activity and the perfusion under each electrode as another measure of local cerebral function.

Methods: EEG mapping was performed simultaneously with H₂¹⁵O positron emission tomography (PET) scanning in 6 normal adult subjects, both at rest and during a simple motor task. EEG data were processed using 3 different montages; two EEG power measures (absolute and relative power) were examined.

Results: Relative power had much stronger associations with perfusion than did absolute power. In addition, calculating power for bipolar electrode pairs and averaging power over electrode pairs sharing a common electrode yielded stronger associations with perfusion than data from referential or single source montages.

Conclusions: These findings indicate (1) that topographic EEG mapping can accurately reflect local brain function in a way that is comparable to other methods, and (2) that the choice of EEG measure and montage have a significant influence on the degree with which maps reflect this local activity and function.