Taroyan N A, Thiyagesh S, Frisby J P, Buckley D, Woodruff P W R, 2002, "Assessment of stereopsis in early stages of Alzheimer's disease using visual evoked potentials" Perception 31 ECVP Abstract Supplement
Assessment of stereopsis in early stages of Alzheimer's disease using visual evoked potentials
N A Taroyan, S Thiyagesh, J P Frisby, D Buckley, P W R Woodruff
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is associated with visuospatial deficits. According to some psychophysical studies, it could also affect stereopsis (Cronin-Golomb, 1995 Gerontologist 35 370 - 376). The aim of our study was to test this possibility electrophysiologically, by recording visual evoked potentials (VEPs) to checkerboard stimuli perceived as moving in depth (stereo condition) or laterally (motion control condition) for 2 s. We tested probable AD patients, age-matched healthy controls, and young healthy participants. There were significant differences between young and elderly participants, such as higher early and decreased later activation in elderly. However, similar differences between stereo and motion conditions were found in both control groups: the latency of stereo VEP peaks was longer than the latency of motion VEP peaks. Differences in stereo and motion specific activation were also reflected in VEP subtraction waveforms. A further analysis revealed that the amplitude and latency of stereo VEP peaks in AD patients were within ±2 SD of the control group's average stereo VEP. These findings show that there were no significant differences in stereo-evoked brain electrical activity between our probable AD patients and the healthy age-matched controls. The implications of these results are discussed.
[We thank our participants for their help and patience, J E W Mayhew and Hector-Gabriel Acosta-Mesa for valuable discussions.]
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