Distinctive features of microsaccades in Alzheimer’s disease and in mild cognitive impairment
During visual fixation, the eyes are never completely still, but produce small involuntary movements, called “fixational eye movements,” including microsaccades, drift, and tremor. In certain neurological disorders, attempted fixation results in abnormal fixational eye movements with distinctive characteristics. Thus, determining how normal fixation differs from pathological fixation has the potential to aid early and differential noninvasive diagnosis of neurological disease as well as the quantification of its progression and response to treatment. Here, we recorded the eye movements produced by patients with Alzheimer’s disease, patients with mild cognitive impairment, and healthy age-matched individuals during attempted fixation. We found that microsaccade magnitudes, velocities, durations, and intersaccadic intervals were comparable in the three subject groups, but microsaccade direction differed in patients versus healthy subjects. Our results indicate that microsaccades are more prevalently oblique in patients with Alzheimer’s disease or mild cognitive impairment than in healthy subjects. These findings extended to those microsaccades paired in square-wave jerks, supporting the hypothesis that microsaccades and square-wave jerks form a continuum, both in healthy subjects and in neurological patients.
KeywordsFixational eye movements Fixation Saccadic intrusions Neurological disorder Dementia
This study was supported by the following funding agencies: CNRS (grant PICS, no. 4197 to ZK), GIS-CNRS, Vieillissement et Longévité (to ZK), the Barrow Neurological Foundation (to SLM and SMC), the National Science Foundation (award 0852636 to SMC), the Arizona Alzheimer’s Consortium (to SMC), and the Science Foundation Arizona Bisgrove Award (to SLM).
Conflict of interest
The authors of this manuscript have no conflicts of interest to disclose.
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