MOTION PERCEPTION AND ALZHEIMERS-DISEASE

The motion sensitivity of 15 probable Alzheimer disease (AD) patients and 15 healthy elderly adults was investigated with a correlated motio n paradigm. The AD patients exhibited significantly higher thresholds for detecting file direction of motion. Contrast sensitivity for a 2 c pd, 7.5 Hz counterphased stimulus was related to motion threshold in t he AD group. There also was a significant relationship between an inde x of dementia severity, Mini-Mental State Exam (MMSE), and motion sens itivity. The results support tire hypothesis proposed from neuroanatom ical evidence by Hof and Morrison (1990) that AD results in a disrupti on of the visual signals mediated by area 17. Further, the data sugges t that this disruption of visual processing is linked to the progressi on of dementia. The study offers support for the hypothesis that AD le ads to a deficit in the magnocellular or M pathway of visual processin g.