Behavioral and cognitive markers of mild cognitive impairment: diagnostic value of saccadic eye movements and Simon task.

Abstract

Mild Cognitive Impairment (MCI) has been considered as a prodromal stage of Alzheimer disease (AD). Subtle changes in specific aspects of executive function like inhibitory control have been found in MCI. We examined attentional and inhibitory control with the aim to distinguish between amnestic MCI patients and healthy controls. Using neuropsychological, behavioral, and oculomotor function experiments, we examined executive function in 59 normal control, 49, multiple domain amnestic MCI (a-MCI) subjects, and 21 early stage AD patients using eye tracking and Simon task as measures of attentional control, to determine which saccade and behavioral tasks were sensitive enough to identify a-MCI. Saccades were investigated in gap and overlap pro-saccade and anti-saccade tasks. Scores on the Simon task were inversely correlated with general cognitive status and can distinguish a-MCI from controls with excellent specificity (AUC = 0.65 for reaction time and 0.59 for false responses). More importantly, our results showed that saccadic gains were affected in a-MCI and were the most sensitive measures to distinguish a-MCI from normal participants AST gap task AUC = 0.7, PST gap task AUC = 0.63, AST overlap task (AUC = 0.73). Moreover, these parameters were strongly correlated with neuropsychological measures. Using tests in parallel model, improved sensitivity up to 0.97. The present results enable us to suggest eye tracking along with behavioral data as a possible sensitive tools to detect a-MCI in preclinical stage.