Introduction

Electroencephalograms (EEGs) from the human scalp were first recorded in 1924 by Hans Berger. It is assumed that they are generated by brain activity related to information processing. EEG is mainly caused by nerve cell activity, whereas other brain imaging methods are more related to blood flow and metabolic parameters. Moreover, the direct coupling of EEG with biological flow of information allows a continuous and chronometric approach to the basis of cognitive processing. Variations of EEG require synchronous and massive parallel activity in wide-ranging populations of neurons and the measures are done in a great distance to the generators. Thus spatial resolution is less than in other brain imaging techniques.

Actually EEG potentials occur in several locations with alternating polarity. This finding is consistent with models ...