Use of VEPs as electrodiagnostic biomarkers of mild cognitive impairment

Abstract

Alzheimer's disease (AD) and its precursor, mild cognitive impairment (MCI), are characterized by early onset of visuospatial impairment along with memory impairment and disorientation. Based on these clinical features, I hypothesized that visual impairment might be a candidate biomarker for early electrodiagnosis of MCI. Therefore, I have been focusing on the application of visual evoked potentials (VEPs) as a non-invasive, simple, and objective method for evaluating visual impairment in MCI patients. In this review, I first outline the concept of the human visual system. Second, I briefly mention the basic technology of VEPs. Then, I describe the previous VEP studies on AD and MCI. These VEP studies have reported that the lower-level visual pathways are less likely to be involved in AD and MCI, whereas the higher-level visual streams frequently show VEP abnormalities. Finally, I introduce my new VEP techniques for examining visual impairment in MCI. VEPs with multimodal visual stimuli (especially, optic flow motion) are useful for distinguishing MCI patients from non-impaired individuals. It may also be feasible to discriminate the type of dementia responsible for MCI. From this review, I stress that VEPs are plausible biomarkers for the early electrodiagnosis of MCI.