Abstract
Our perception of the world is remarkably stable despite of distorted retinal input due to frequent eye movements. It is considered that the brain uses corollary discharge, efference copies of signals sent from motor to visual regions, to compensate for distortions and stabilize visual perception. In this study, we tested whether patients with Alzheimer’s disease (AD) have impaired corollary discharge functions as evidenced by reduced compensation during the perception of optic flow that mimics self-motion in the environment. We asked a group of early-stage AD patients and age-matched healthy controls to indicate the perceived direction of self-motion based on optic flow while tracking a moving target with smooth pursuit eye movement, or keeping eye fixation at a stationary target. We first replicated the previous findings that healthy participants were able to compensate for distorted optic flow in the presence of eye movements, as indicated by similar performance of self-motion perception between pursuit and fixation conditions. In stark contrast, AD patients showed impaired self-motion perception when the optic flow was distorted by eye movements. Our results suggest that early-stage AD pathology is associated with disrupted eye movement compensation during self-motion perception.
Highlights
In addition to the progressive loss of memory and cognitive functions, patients with Alzheimer’s disease (AD) at the early stage often exhibit declined visuospatial capabilities[1, 2]
The current study revealed that AD pathology is associated with disrupted eye movement compensation during the perception of optic flow
We showed that both the sensitivity and bias of optic flow perception were impaired in AD patients in the presence of pursuit eye movement
Summary
In addition to the progressive loss of memory and cognitive functions, patients with Alzheimer’s disease (AD) at the early stage often exhibit declined visuospatial capabilities[1, 2]. Comparing to healthy elderly individuals, AD patients possess elevated optic flow thresholds[6] and are worse at perceiving and steering in the direction of self-motion based on the pattern of optic flows[7]. Consistent with these behavioral deficiencies, imaging studies have revealed that AD patients have noticeable atrophy in the superior parietal lobules[8, 9] and they show reduced activations in dorsal visual stream areas that are implicated in visuosptial processing[10,11,12]. We will compare the performance of optic flow perception between a group of AD patients and age-matched healthy elder participants, under the condition of either smooth pursuit eye movements or pure fixations
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