title: Neurophysiologic analyses of low- and high-level visual processing in Alzheimer disease.
abstract: OBJECTIVE
  We developed visual motion evoked potential (EP) measures related to navigational impairment in Alzheimer disease (AD) and have now applied these methods to explore the role of elementary perceptual and attentional mechanisms mediating these effects.
  
  
  METHODS
  Older adult (OA) control subjects and AD patients underwent visual motion perceptual testing, attentional performance monitoring, and basic neuropsychological and visual assessments. We recorded stationary pattern onset and visual motion onset EPs as well as behavioral event-related potentials during centered visual fixation.
  
  
  RESULTS
  Psychophysical assessment demonstrated visual motion perceptual impairments in patients with AD, half of whom also showed low sensitivity in the attentional task. The low sensitivity AD patients had small pattern onset and absent motion onset EPs, whereas the high sensitivity AD patients had large pattern onset EPs and normal motion onset EPs.
  
  
  CONCLUSIONS
  We conclude that visual evoked potentials (EPs) are abnormal in all patients with Alzheimer disease (AD): Those with small pattern and motion onset EPs may have greater AD pathology in visual cortex, whereas those with larger pattern onset EPs may have greater AD pathology in higher centers. These findings highlight the utility of visual EPs in distinguishing between syndromic variants of AD associated with particular patterns of functional decline.
authors.affiliation: Department of Neurology, University of Rochester Medical Center, Rochester, NY 14642-0673, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Fernandez
authors.forename: Voyko
authors.initials: V
authors.lastname: Kavcic
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Duffy
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000503:physiopathology; D001288:Attention / Q000502:physiology; D004569:Electroencephalography / Q000379:methods; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology; D009460:Neurologic Examination / Q000379:methods; D009483:Neuropsychological Tests; D009949:Orientation / Q000502:physiology; D010468:Perceptual Disorders / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D011237:Predictive Value of Tests; D013028:Space Perception / Q000502:physiology; D014786:Vision Disorders / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D014793:Visual Cortex / Q000503:physiopathology*; D014795:Visual Pathways / Q000503:physiopathology*