Deficits in saccadic eye movements differ between subtypes of patients with mild cognitive impairment

Introduction: Mild cognitive impairment (MCI) is known to be heterogeneous in its cognitive features and course of progression. Whilst memory impairment is characteristic of amnestic MCI (aMCI), cognitive deficits other than memory can occur in both aMCI and non-amnestic MCI (naMCI) and accurate assessment of the subtypes of MCI is difficult for clinicians without the application of extensive neuropsychological testing. In this study, we examine metrics derived from recording of reflexive and voluntary saccadic eye movements as a potential alternative method for discriminating between subtypes and assessing cognitive functions in MCI.Method: A total of 29 MCI patients and 29 age- and education-matched healthy controls (HCs) participated in the cross-sectional study. We recorded horizontal and vertical pro-saccades and anti-saccade responses. All the participants also completed a comprehensive neuropsychological tests battery.Results: Significant differences in saccadic eye movement were found between the subtypes of MCI and HCs. Patients with aMCI had a higher percentage of short latency "express" saccades than HCs. We found strong associations between saccadic reaction times and cognitive domains, including executive functions and attention. The mini-mental state examination (MMSE) was also found to correlate with uncorrected errors in the anti-saccade task.Conclusions: The increased proportion of saccades in the express latency range in aMCI may be indicative of problems with cognitive inhibitory control in these patients. A focus on this and other saccade metrics in the preclinical and prodromal stages of dementia may help to predict the clinical progression of the disease and direct interventions for the management of MCI. The clinical significance of saccadic eye movement impairments in MCI is not yet fully understood and should be investigated in further studies using larger samples.