Clinicophysiological study of motion-related visual evoked potentials (MVEPs)

The purpose of this study was to elucidate whether there is any difference between dementia of the Alzheimer's type (DAT) and multi-infarct dementia (MID) in MVEPs evoked by coherent motion (CM) and those evoked by random motion (RM). The subjects included 11 DAT and 13 MID patients, and 18 normal controls in their 60s to 70s. The subjects were instructed to fix their eyes on the center of a CRT placed 80 cm away from them. On each CRT, 100 solid circles 4 mm in diameter were continuously displayed showing CM or RM 10 mm from the original sites individually 20 and 80% of the time, respectively, at a frequency of 0.6 Hz. Electroencephalograms were recorded from 15 sites on the scalp referenced to linked earlobes following CM and RM. A positive wave was evoked at a latency of about 110 ms dominantly from O1 and O2. This component was significantly (p < 0.05) delayed following RM in DAT patients compared to normal controls, significantly (p < 0.05) correlated with mini-mental state examination scores, and significantly (p < 0.05) delayed in DAT patients who were unable to perceive CM compared to those who could. In conclusion. MVEP was a useful tool to evaluate perception of motion in DAT.