Measurement of mental fatigability by task related spectral EEG. A pilot study

Task related EEG spectra are promising markers of mental activity. But the cooperation of the patients necessary for the registration limits its application in the neuro-psychiatry.

EEG difference spectra on counting (EDSC)--was developed to detect the effect of a short calculation task on the spectral EEG. The originality of the task situation is a continuous mental work in a very short period of time, while the level of task difficulty is adapted to the patient's actual mental capacity. While the rest pre-task and the post task EEG sections were compared, the results show the mental "EEG fatigability" caused by the short intensive cognitive activity. The first preliminary results have been demonstrated by a comparative study of two healthy and three patient (probable Alzheimer disease, post-stroke state without mental deficit and mixed type of dementia) groups.

Similarly to the findings of other authors, in addition to the differences of the alpha band seen on the temporo-parieto-occipital regions, the frontal localization and the beta band seem to be prominent, too. Demented patients had stronger EEG reactions than post-stroke patients without mental deficits and healthy elder persons had more extensive changes than the younger ones.

The test can be considered as indirect marker showing the different mental fatigability in diverse pathological conditions and during the aging process. Effect of therapeutic processes can also be followed based on "key-lock principle". Standardization of the test is essential for the introduction of EDSC to the every-day routine of clinical neuropsychiatry.