Characterizing the Relationship Between Eye Movement Parameters and Cognitive Functions in Non-demented Parkinson's Disease Patients with Eye Tracking

Summary

Here, we present a protocol to study the relationship between the eye movement parameters and cognitive functions in non-demented Parkinson's disease patients. The experiment used an eye tracker to measure the saccadic amplitude and fixation duration in a visual search task. The correlation with performance in multi-domain cognitive tasks was subsequently measured.

Abstract

Cognitive impairment is a common phenomenon in Parkinson’s disease that has implications on the prognosis. A simple, noninvasive and objective proxy measurement of cognitive function in Parkinson’s disease will be helpful in detecting early cognitive decline. As a physiological metric, eye movement parameter is not confounded by the subject's attributes and intelligence and can function as a proxy marker if it correlates with cognitive functions. To this end, this study explored the relationship between the eye movement parameters and performance in cognitive tests in multiple domains. In the experiment, a visual search task with eye tracking was set up, where subjects were asked to look for a number embedded in an array of alphabets scattered randomly on a computer screen. The differentiation between the number and the alphabet is an overlearned task such that the confounding effect of cognitive ability on the eye movement parameters is minimized. The average saccadic amplitude and fixation duration were captured and calculated during the visual search task. The cognitive assessment battery covered domains of frontal-executive functions, attention, verbal and visual memory. It was found that prolonged fixation duration was associated with poorer performance in verbal fluency, visual and verbal memory, allowing further exploration on the use of eye movement parameters as proxy markers for cognitive function in Parkinson’s disease patients. The experimental paradigm has been found to be highly tolerable in our group of Parkinson's disease patients and could be applied transdiagnostically to other disease entities for similar research questions.

Introduction

Parkinson’s disease is classically a motor disorder; yet, the disease is also associated with cognitive deficits, and progression into dementia is common¹. The pathophysiology of cognitive impairment in Parkinson's disease is not well understood. It is thought to be related to alpha-synuclein deposition in the cortical area based on Braak's staging². It was also proposed that a dual syndrome of degeneration of the dopaminergic and the cholinergic system leads to different cognitive deficits with prognostic implication³. More research is needed to further elucidate the exact mechanism....

Protocol

This research project was approved by the Joint Chinese University of Hong Kong-New Territories East Cluster Clinical Research Ethics Committee (CREC Ref. No.: 2015.263).

1. Participants Recruitment and Baseline Assessment

1. Recruit Parkinson's disease patients aged less than or equal to 70 from a neurology specialist clinic with the diagnosis made based on the United Kingdom Parkinson's Disease Society (UKPDS) Brain Bank Diagnostic Criteria¹²........

Discussion

The protocol presented above was designed as the first part of a longitudinal study in exploring the potential clinical utility of eye movement parameters as surrogate markers for cognitive functions in Parkinson's disease. While there are studies that examine more classical eye tracking paradigms such as self-paced saccade, reflexive saccade, and anti-saccade^25,26,27, a visual search task was used in this study to measure e.......

Materials

Name	Company	Catalog Number	Comments
Computer	Intel
Computerized cognitive assessment tool	CANTAB	CANTAB Research Suite	Contains Pattern Recognition Memory, Spatial Span, and Stockings of Cambridge
Eye Movement Analyzer	Lab Viso Limited		https://github.com/lab-viso-limited/visual-search-analyzer
Eye tracker	Tobii	Tx300	23 inch computer screen with resolution of 1920x1080, Sampling rate at 300Hz
Hong Kong List Leanrning Test	Department of Psychology, The Chinese University of Hong Kong	The Hong Kong List Learning Test (HKLLT) 2nd Edition
Stroop test	Laboratory of Neuropsychology, The University of Hong Kong	Neuropsychological Measures: Normative Data for Chinese, Second Edition (Revised)
Tobii Studio	Tobii	Tobii Studio version 3.2.2	Computer programme for running the visual search task
Visual Search Task	Lab Viso Limited		https://www.labviso.com/#products