Electrophysiological biomarkers for improved etiological diagnosis of cognitive impairment

Abstract

Alzheimer's disease (AD), Lewy body disease (LBD), and frontotemporal lobar degeneration (FTLD) are three major types of neurodegenerative dementia. Intervention and treatment differ significantly among these major dementias, necessitating early and accurate diagnosis. Patients with AD, LBD, and FTLD exhibit specific patterns of visual dysfunction as early behavioral signs. These visual impairments are the manifestations of topographic patterns of neuropathology specific to each type of dementia. Electrophysiological measurements, such as visual evoked potentials and event-related potentials, are objective and noninvasive tools that can detect subtle functional changes in human brain. Therefore, with the use of visual evoked potentials and event-related potentials, early detection of specific patterns of visual dysfunction may be useful for differential diagnosis of dementia. In this review, we first summarize current knowledge about the relevant aspects of the human visual system. Second, we outline clinical characteristics, including visual perceptual abnormalities, of each type of degenerative demen- tia. Finally, we describe the application of visual evoked potential and event-related potential recording techniques to study visual perception in patients with mild cognitive impairment (prodromal stage of dementia). We stress that electrophysiological signals have potential as reliable biomarkers in the diagnosis of different types of dementia, especially in the case of overlapping phenotypes.