PATTERN VISUAL-EVOKED POTENTIAL MAPPING IN ALZHEIMERS-DISEASE - CORRELATIONS WITH VISUOSPATIAL IMPAIRMENT

We evaluated pattern visual evoked potentials (PVEPs) in patients with Alzheimer's disease (AD) and correlated the neurophysiological result s with visuospatial performances in order to understand better the und erlying causes of visual disturbances. Latencies and topographical dis tribution of PVEP components were evaluated in 20 AD patients who unde rwent an extensive battery of neuropsychological tests. Mean latencies of N70 and P100 were normal in AD patients, while mean latencies of N 140 and P200 were significantly increased in comparison with age-match ed healthy controls. The topographical distribution of PVEP components did not show any significant difference between the two groups. Visuo spatial impairment was detected in 8 patients (40%). Statistically sig nificant positive correlations were observed between P200 amplitude (p osterior right hemisphere mean z score) and performance in visuospatia l tests. Our data are consistent with a sparing of foveal retinocortic al pathways and with the selective dysfunction of either corticocortic al connections between the striate cortex and the visual associative s tructures or of right temporo-parieto-occipital visual analyzers.