Early detection of cognitive decline in Alzheimer’s disease using eye tracking

 Didn't your competent? doctor create an eye tracking protocol over a decade ago?NO? So, you DON'T have a functioning stroke doctor, do you? 

eye tracking (15 posts to June 2013)

Early detection of cognitive decline in Alzheimer’s disease using eye tracking

Shin-ichi Tokushige^1,2Hideyuki Matsumoto³Shun-ichi Matsuda⁴Satomi Inomata-Terada⁵Naoki Kotsuki²Masashi Hamada¹Shoji Tsuji^1,6Yoshikazu Ugawa⁷Yasuo Terao^1,5*

• ¹Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
• ²Department of Neurology, Kyorin University, Tokyo, Japan
• ³Department of Neurology, Mitsui Memorial Hospital, Tokyo, Japan
• ⁴Department of Neurology, NTT Medical Center Tokyo, Tokyo, Japan
• ⁵Department of Medical Physiology, Kyorin University, Tokyo, Japan
• ⁶Institute of Medical Genomics, International University of Health and Welfare, Chiba, Japan
• ⁷Department of Human Neurophysiology, Fukushima Medical University, Fukushima, Japan

Background: Patients with Alzheimer’s disease (AD) are known to exhibit visuospatial processing impairment, as reflected in eye movements from the early stages of the disease. We investigated whether the pattern of gaze exploration during visual tasks could be useful for detecting cognitive decline at the earliest stage.

Methods: Sixteen AD patients (age: 79.1 ± 7.9 years, Mini Mental State Examination [MMSE] score: 17.7 ± 5.3, mean ± standard deviation) and 16 control subjects (age: 79.4 ± 4.6, MMSE score: 26.9 ± 2.4) participated. In the visual memory task, subjects memorized presented line drawings for later recall. In the visual search tasks, they searched for a target Landolt ring of specific orientation (serial search task) or color (pop-out task) embedded among arrays of distractors. Using video-oculography, saccade parameters, patterns of gaze exploration, and pupil size change during task performance were recorded and compared between AD and control subjects.

Results: In the visual memory task, the number of informative regions of interest (ROIs) fixated was significantly reduced in AD patients compared to control subjects. In the visual search task, AD patients took a significantly longer time and more saccades to detect the target in the serial but not in pop-out search. In both tasks, there was no significant difference in the saccade frequency and amplitude between groups. On-task pupil modulation during the serial search task was decreased in AD. The number of ROIs fixated in the visual memory task and search time and saccade numbers in the serial search task differentiated both groups of subjects with high sensitivity, whereas saccade parameters of pupil size modulation were effective in confirming normal cognition from cognitive decline with high specificity.

Discussion: Reduced fixation on informative ROIs reflected impaired attentional allocation. Increased search time and saccade numbers in the visual search task indicated inefficient visual processing. Decreased on-task pupil size during visual search suggested decreased pupil modulation with cognitive load in AD patients, reflecting impaired function of the locus coeruleus. When patients perform the combination of these tasks to visualize multiple aspects of visuospatial processing, cognitive decline can be detected at an early stage with high sensitivity and specificity and its progression be evaluated.