Visual masking: a reliable measure for the assessment of cognitive dysfunction in the elderly?

Reliable assessment of cognitive dysfunction in the elderly is a prerequisite for the evaluation of treatment of age-related cognitive decline. Psychophysical thresholds are known to be more reliable than psychometric tests, as assessed by stability of performance in visual masking. A backward (Till & Franklin, 1981) and a forward masking study (Coyne, 1981) were replicated. Thereafter, the same volunteers carried out a backward and forward masking task adapted to minimize noncognitive age-related influences: target and mask duration were individually adjusted to control for reduced eye transmissiveness. Attention was assessed with the electrooculogram; a dependent variable insensitive to sporadic decreases of attention was selected. Test-retest stability in the elderly after 2-4 weeks was r = .97 in backward and r = .86 in forward masking. As Alzheimer's disease mainly affects the cortex, backward masking, which is primarily cortical, may be useful to assess aspects of cognitive dysfunction.