To determine whether motion sensitivity varies with age, we measured motion discrimination in visual normals 25 to 80 years of age and found that motion thresholds increased linearly with age and were approximately two times higher in those 70 to 80 years old than in participants under thirty. This increase was not attributable to pupil size or retinal image distortion, but probably reflects neurodegeneration in the primary visual pathway. We compared the motion sensitivity of patients with senile dementia of the Alzheimer type (SDAT) with results from a subset of the visual normals of similar age. In SDAT patients, there were significant threshold elevations, which were more pronounced in the patients with more severe dementia. These findings confirm previous reports of visual system involvement in SDAT and indicate motion testing may reveal preclinical visual system involvement in SDAT.
The results indicate motion detection and perception thresholds deteriorate with age. This may reflect a susceptibility to age-related degeneration in specific cortical areas responsible for motion perception as well as neurodegeneration in the retinogeniculate pathway.
To better understand the damage to the motion pathway that occurs in senile dementia of the Alzheimer type (SDAT), we developed a system to assess separately the conscious perception and unconscious detection of motion in patients with SDAT. Motion perception thresholds were significantly elevated in SDAT (n = 9) compared with controls (n = 12), but motion detection thresholds were normal. This dissociation between the perception and detection of motion in early SDAT parallels histologic evidence of a disconnection between primary and association visual cortices. This disconnection may underlie the severe visual perception deficits seen in SDAT.
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