Name: characterizing the relationship between eye movement parameters and cognitive functions in non-demented parkinson's disease patients with eye tracking
Uploaded: 2019-09-26T14:30:00
Description: Watch this Scientific Journal Video about Characterizing the Relationship Between Eye Movement Parameters and Cognitive Functions in Non-demented Parkinson's Disease Patients with Eye Tracking at JoVE

The authors would like to thank Dr. Harvey Hung for his advice&#160;on the manuscript.

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
<ol>
	<li>Recruit Parkinson&#39;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&#39;s Disease Society (UKPDS) Brain Bank Diagnostic Criteria12....

<ol>
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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visual+exploration+in+Parkinson's+disease+and+Parkinson's+disease+dementia.">Visual exploration in Parkinson's disease and Parkinson's disease dementia.</a> Brain. 136 (3), 739-750 (2013).</li><li>Litvan, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnostic+criteria+for+mild+cognitive+impairment+in+Parkinson's+disease:+Movement+Disorder+Society+Task+Force+guidelines.">Diagnostic criteria for mild cognitive impairment in Parkinson's disease: Movement Disorder Society Task Force guidelines.</a> Movement Disorders. 27 (3), 349-356 (2012).</li><li>R&#246;sler, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alterations+of+visual+search+strategy+in+Alzheimer's+disease+and+aging.">Alterations of visual search strategy in Alzheimer's disease and aging.</a> Neuropsychology. 14 (3), 398-408 (2000).</li><li>Hughes, A. 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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&#39;s disease. While there are studies that examine more classical eye tracking paradigms such as self-paced saccade, reflexive saccade, and anti-saccade25,26,27, a visual search task was used in this study to measure e...

Parkinson&#8217;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&#39;s disease is not well understood. It is thought to be related to alpha-synuclein deposition in the cortical area based on Braak&#39;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 mechanisms involved in cognitive impairment in Parkinson&#39;s disease. On the clinical aspect, the presence of cognitive impairment has a significant impact on prognosis4,5. Assessment of cognitive function in clinical practice is, therefore, essential. However, a lengthy cognitive assessment is limited by patients&#8217; mental and motor conditions. Therefore, a noninvasive and simple measurement that can reflect the disease&#39;s burden on cognitive function is needed.
The eye movement abnormalities are widely described detectable signs of Parkinson&#39;s disease from its early stages6, yet the pathophysiology is even less well-characterized than that of cognitive impairment. The generation of eye movement is through a transformation of the visual sensory input, subserved by an intertwined cortical and subcortical network, into signals to the oculomotor nuclei in the brainstem for effect7. Involvement of Parkinson&#39;s disease pathologies in these networks may lead to observable eye movement abnormalities. There is, perhaps overlapping of neuroanatomical structures that govern the control of eye movement and cognitive function. Furthermore, there have been studies examining the relationship between saccadic eye movement and cognitive function in other neurodegenerative disorders8. On such grounds, it is worthwhile to explore the use of eye movement parameters as a proxy marker of cognitive functions in Parkinson&#39;s disease. One cross-sectional study9 showed that reduced saccadic amplitude and longer fixation duration was associated with the severity of global cognitive impairment in Parkinson&#39;s disease. However, there is a lack of data on the correlation between eye movement parameters and specific cognitive domains. The significance and need of measurement of specific cognitive domains, rather than a general cognitive state, is that individual cognitive domain informs differential prognostic information in Parkinson&#39;s disease3 and they are subserved by different neural networks. The aim of this study is to explore the specific relationship between eye movement metrics and different cognitive functions. This is the first step to establish a foundation on which the development of biomarkers of cognitive decline in Parkinson&#39;s disease using eye tracking technology could be built.
The experimental paradigm presented is composed of 2 major parts: the cognitive assessment and the eye tracking task. The cognitive assessment battery encompassed a range of cognitive functions, including attention and working memory, executive function, language, verbal memory and visuospatial function. The choice of these 5 cognitive domains is based on the Movement Disorder Society Task Force Guidelines for the mild cognitive impairment in Parkinson&#39;s disease10, and a set of locally available cognitive tests were selected to build the assessment battery. In a previous similar eye tracking study on Parkinson&#39;s disease cognition mentioned9, the author extracted the eye movement parameters while the subjects were engaged in visual cognitive tasks, where the parameters may potentially be influenced by the subject&#39;s cognitive ability. As this study aimed to assess the correlation between the eye movement parameters and different cognitive domains, the potential confounding effect of cognitive abilities on the eye parameters must be addressed. In this regards, a visual search task, adapted from another eye tracking study on Alzheimer&#8217;s disease11, was employed to capture the eye movement parameters of the subjects. During the task, subjects had to search for a single number on a computer screen among multiple alphabet distracters. This task would elicit the alternate use of saccadic eye movement and visual fixation, the abnormalities of which are described widely in Parkinson&#39;s disease. The identification and differentiation of number and alphabet is an overlearned task where the demand for cognitive functions is only minimal and would, therefore, be suitable to answer the research question of this study. A computer program was developed based on the specifications and design as stated by R&#246;sler et al.11. in their original study to be run within the in-built software of our eye tracker. An in-house algorithm for classification and analysis of the eye tracking data was also developed for this study.

<table border="0" cellpadding="0" cellspacing="0" style="width:1008px;" width="1007">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Computer&#160;</td>
			<td style="width:121px;">Intel</td>
			<td style="width:505px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Computerized cognitive assessment tool</td>
			<td style="width:121px;">CANTAB</td>
			<td style="width:505px;">CANTAB Research Suite</td>
			<td>Contains Pattern Recognition Memory, Spatial Span, and Stockings of Cambridge</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Eye Movement Analyzer</td>
			<td style="width:121px;">Lab Viso Limited</td>
			<td style="width:505px;"></td>
			<td>https://github.com/lab-viso-limited/visual-search-analyzer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Eye tracker</td>
			<td style="width:121px;">Tobii</td>
			<td style="width:505px;">Tx300</td>
			<td>23 inch computer screen with resolution of 1920x1080, Sampling rate at 300Hz</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:215px;">Hong Kong List Leanrning Test</td>
			<td style="width:121px;">Department of Psychology, The Chinese University of Hong Kong</td>
			<td style="width:505px;">The Hong Kong List Learning Test (HKLLT) 2nd Edition</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:215px;">Stroop test</td>
			<td style="width:121px;">Laboratory of Neuropsychology, The University of Hong Kong</td>
			<td style="width:505px;">Neuropsychological Measures: Normative Data for Chinese, Second Edition (Revised)</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Tobii Studio</td>
			<td style="width:121px;">Tobii</td>
			<td style="width:505px;">Tobii Studio version 3.2.2</td>
			<td>Computer programme for running the visual search task</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Visual Search Task</td>
			<td style="width:121px;">Lab Viso Limited</td>
			<td style="width:505px;"></td>
			<td>https://www.labviso.com/#products</td>
		</tr>
	</tbody>
</table>

characterizing the relationship between eye movement parameters and cognitive functions in non-demented parkinson's disease patients with eye tracking

Cognitive impairment is a common phenomenon in Parkinson&#8217;s disease that has implications on the prognosis. A simple, noninvasive and objective proxy measurement of cognitive function in Parkinson&#8217;s disease will be helpful in detecting early cognitive decline. As a physiological metric, eye movement parameter is not confounded by the subject&#39;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&#8217;s disease patients. The experimental paradigm has been found to be highly tolerable in our group of Parkinson&#39;s disease patients and could be applied transdiagnostically to other disease entities for similar research questions.

The full result of this study is available in the original paper published23. Parkinson&#8217;s disease subjects (n = 67) were recruited and completed the assessment. However, 5 cases failed to complete the visual search task as they wore progressive lens incompatible with the eye tracker and their data was discarded. The mean age of the subjects was 58.9 years (SD = 7.5 years) with a male to female ratio of 1.7:1. 62 healthy age-, sex-, and education-matched controls were recruited for comparison...

Watch this Scientific Journal Video about Characterizing the Relationship Between Eye Movement Parameters and Cognitive Functions in Non-demented Parkinson's Disease Patients with Eye Tracking at JoVE

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

Here, we present a protocol to study the relationship between the eye movement parameters and cognitive functions in non-demented Parkinson&#39;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.

Cognitive impairment is a common phenomenon in Parkinson&#8217;s disease that has implications on the prognosis. A simple, noninvasive and objective proxy ...

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