The influence of stimulus eccentricity on prosaccade outcomes in patients with Alzheimer's Disease dementia at an early stage and amnestic mild cognitive impairment

Introduction: Prosaccade task is a widely used objective method to evaluate reflexive saccade and visual attention. The study aimed to investigate prosaccade stimulus eccentricity, compare prosaccade parameters in patients with Alzheimer's disease dementia (AD), amnestic mild cognitive impairment (aMCI), and neurotypical adults (NA), and examine the relationship between prosaccade and neuropsychological tests. Methods: Thirty patients with AD, 34 with aMCI, and 32 NA were included in the study. Eye movements were recorded with the EyeLink 1000 Plus in the prosaccade task, and this study evaluated cognitive function with comprehensive neuropsychological tests assessing attention, memory, executive function, visuospatial function, and language domains. Results: The correct saccade rates of patients with AD were significantly lower than NA in the 5 degrees and 10 degrees stimulus eccentricities. Patients with AD had significantly longer latencies in the 10 degrees stimulus eccentricity than those with aMCI and NA. Patients with aMCI did not differ in prosaccade performance compared to NA. Prosaccade parameters were significantly correlated with all cognitive domains. As the amplitude of the stimuli increased, the rate of correct saccades decreased, while the express saccade rate, latency, amplitude, and peak velocity increased. Conclusion: Our findings that correct saccade rates and latency may be distinguishing parameters of early AD are promising. This study also found that stimulus eccentricity affects prosaccade measures in AD, MCI, and NA.