Attentional Distractibility Induced by Optokinetic Stimulation in Mild Cognitive Impairment

A recent study has shown that optokinetic stimulation (OKS) can induce attentional distractibility in Alzheimer disease (AD). In this study, we investigated whether OKS also perturbs balanced attentional deficit in patients with amnestic mild cognitive impairment (aMCI), a prodromal phase of AD, and explored whether the effects of OKS at baseline differ between aMCI patients who convert to AD at follow-up (converters) and those who do not (nonconverters). A total of 44 patients with aMCI, 14 patients with subcortical vascular mild cognitive impairment (svMCI), and 35 age-matched and education-matched normal controls were studied for their ability to bisect solid lines superimposed on a background of OKS. Background OKS movements were either leftward or rightward, or were stationary. A total of 33 of the 44 patients with aMCI were clinically followed for an average of 2.8 years, of which there were 15 converters and 18 nonconverters. Under both the leftward and rightward movement conditions, the magnitudes of line bisection errors (LBEs) in aMCI patients were greater than in normal controls. However, there were no differences in LBEs between svMCI patients and normal controls or between aMCI and svMCI patients. Baseline LBEs of aMCI converters were significantly greater than those of nonconverters in both leftward and rightward movement conditions. These results may indicate that OKS is useful for detecting AD at a very early stage and for predicting the conversion of aMCI to AD.