[Perceptibility and differentiation of local effects-comparison between Hjorths source-derivation and conventional...

Using Hjorths source derivation for more than four years 1034 routine EEG were evaluated by means of a classifiying evaluation-sheet. Ten variations of local effects were defined by materials requirements. Detection and differentiation of those local effects compared in reference, bipolar and common reference recordings and source derivation. It is shown that all information received from standard recordings is also evident in source derivation. Furthermore there are a lot of additional findings and - proved by illustrating examples - a respectable number of findings which could not be detected by standard recordings. A spatial model figures the superiority of source derivation in detection and discrimination of local effects.