[Topography of P300 in psychiatry--II. Cognitive P300 fields in dementia].

The P300 wave undergoes alterations during physiological aging showing lower amplitudes and longer latencies in geriatric controls. By means of topographical display of P300-data it could be shown that the topography with maximal positivity at parietal sites is maintained in aging. In patients, however, suffering from senile dementia of Alzheimer's type signs of a frontal elevation and a parietal decrement of P300 amplitudes could be observed. The findings can be interpreted firstly as an indication that the frontal lobe is less effected. On the other side if a hippocampal dipole is assumed a neuronal lesion could lead to a turn of this dipole with the result of a now frontally located positivity.