Visual Motion Event Related Potentials Distinguish Aging and Alzheimer's Disease

Background: Aging and Alzheimer's disease (AD) disrupt visuospatial processing and visual motion evoked potentials in a manner linked to navigational deficits. Objective: Our goal is to determine if aging and AD have distinct effects on visual cortical motion processing for navigation. Methods: We recorded visual motion event related potentials (ERPs) in young (YNC) and older normal controls (ONC), and early AD patients (EADs) who viewed rapidly changing optic flow stimuli that simulate naturalistic changes in heading direction, like those that occur when following a path of self-movement through the environment. After a random series of optic flow stimuli, a vertical motion stimulus was presented to verify sustained visual attention by demanding a rapid push-button response. Results: Optic flow evokes robust ERPs that are delayed in aging and diminished in AD. The interspersed vertical motion stimuli yielded shorter N200 latencies in EADs, matching those in ONCs, but the EADs' N200 amplitudes remained small. Conclusions: Aging and AD have distinct effects on visual sensory processing: aging delays evoked response, whereas AD diminishes responsiveness.