Reflection of mental exercise in the dynamic quantitative topographical EEG.

The aim of this study was to investigate the activation process of the central nervous system during mental demand in a complex psychophysiological situation. A 17-channel quantitative topographical EEG was recorded in 48 healthy volunteers (male and female, aged 49 +/- 6 years), using the CATEEM system, during four different psychometric tests (simple reaction time measurement, concentration performance, figure detection and word recall test). The mental load varied with each test, producing a graduated increase in spectral power density in delta and theta frequency range on the EEG in the fronto-temporal, parietal and occipital regions of the cortex and a generalized decrease in alpha power. During the rest periods after each test a graduated increase in alpha 1 power was seen as a possible expression of change in vigilance level. With this method we were able to differentiate two effects of psychometric tests on brain activity: the actual mental demand itself and the influence on the vigilance level.