[Topographic analysis of resting EEG and photic driving responses in patients with presenile Alzheimer's disease].

Topographic analysis of the resting EEG was performed in nine patients with presenile Alzheimer's disease(AD) and nine sex- and age-matched normal subjects. We also analyzed EEG activity recorded during photic stimulation(5, 10 and 15 Hz) to evaluate photic driving responses. The square root of absolute power was determined for each frequency band using a Fast Fourier Transform. Compared with the controls, the AD patients had increased delta and theta in the resting EEG mainly over the frontal regions. The patients also had reduced alpha and beta, and did not show posterior predominance of alpha activity. EEG analysis during photic stimulation showed that the patients had a reduction in photic driving responses, and significant topographic differences were found over the parieto-occipital regions. These findings provide further evidence that AD patients have background EEG slowing with a reduction in alpha and fast activity. They also suggest an impairment of visual functioning in AD.