CONTRAST SENSITIVITY IN ALZHEIMERS-DISEASE - A 1-YEAR LONGITUDINAL ANALYSIS

Spatial contrast sensitivity was evaluated in normal elderly adults an d a group with probable Alzheimer's disease (AD) in three sessions ove r a 1-year period. There was evidence of a reduction over 1 year in co ntrast sensitivity for static, high spatial frequencies in both groups of subjects. A striking difference between the subject groups was obs erved in their response to flickered stimuli. Although normal elderly adults yielded good stability in sensitivity for both static and flick ered spatial frequencies over the 1 year, AD patients experienced a si gnificant decline in response to flickered (7.5 Hz) stimuli. The signi ficant decline in sensitivity for low contrast, high temporal events i n AD patients is consistent with reports of cell loss at the retinal a nd cortical levels of the magnocellular (M) channel in AD. Thus, the s patial contrast sensitivity change in AD may reflect a more rapid loss of cells specifically in the M channel over a 1-year period.