Duration of EEG alpha wave blockade by tone stimulation is prolonged in early stage of presenile onset dementia of the Alzheimer type.

The EEG alpha rhythm suppression by sudden unexpected tones in a relaxed wakefulness state (Berger response) was measured in four groups of patients and healthy control subjects. One patient group with early cognitive deficits probably caused by a mild stage of presenile onset primary degenerative dementia of the Alzheimer type (DAT), a second patient group with cardiovascular disease and a stage of questionable dementia, an age-matched group of older healthy control subjects and a younger control group. Only half of the DAT group in the mild stage had significantly prolonged Berger responses and a retarded or disturbed habituation. In agreement with other data of their cognitive deficits this indicated a weakening in focussing attention and selective inhibition.