People with Parkinson's often have subtle cognitive changes and a particular area of difficulty is in visuo-perceptual problems. Patients commonly report visual hallucinations - from very subtle "passage hallucinations" - the sense that there is some movement in the periphery of vision to more complex "formed" hallucinations of animals and people. It is now clear that the visual problems affect all aspects of the visual pathway, from the retina to higher processing areas in the brain.
This understanding underpins the work presented here by one of our collaborators, Dr Rimona Weil. She has developed online visual tasks which are sensitive to some of these issues. Her 6 tests covered different aspects of visual processing; the test for object invariance, the ability to detect an image despite distortion is shown in the image below. Also tested were peripheral vision, the ability to detect hidden images, to detect biological motion, relative sizes of shapes and mental rotation.
Image from the Cats-and-Dogs Test, which assesses object invariance. From https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765443/
Interestingly, not all the tests differentiated Parkinson's patients from healthy participants. The distorted image was particularly sensitive to detect differences between groups but the results from mental rotation and subjective size perception were similar.
The importance of these findings - that a short online test performed remotely can detect differences between Parkinson's patients and healthy older people - opens up many possibilities. These kinds of tools are likely to find a role in remote monitoring of patients, especially those who find it difficult to attend clinic. Here at PREDICT-PD we are interested in using these tests for screening and will be working with Dr Weil to find out whether any of the changes in visual processing are present before diagnosis of Parkinson's.
-Anna
https://www.ncbi.nlm.nih.gov/pubmed/29473691
Weil RS, Schwarzkopf DS, Bahrami B, Fleming SM, Jackson BM, Goch TJC, Saygin AP, Miller LE, Pappa K, Pavisic I, Schade RN, Noyce AJ, Crutch SJ, O'Keeffe AG, Schrag AE, Morris HR
BACKGROUND:
People with Parkinson's disease (PD) who develop visuo-perceptual deficits are at higher risk of dementia, but we lack tests that detect subtle visuo-perceptual deficits and can be performed by untrained personnel. Hallucinations are associated with cognitive impairment and typically involve perception of complex objects. Changes in object perception may therefore be a sensitive marker of visuo-perceptual deficits in PD.
We developed an online platform to test visuo-perceptual function. We hypothesised that (1) visuo-perceptual deficits in PD could be detected using online tests, (2) object perception would be preferentially affected, and (3) these deficits would be caused by changes in perception rather than response bias.
We assessed 91 people with PD and 275 controls. Performance was compared using classical frequentist statistics. We then fitted a hierarchical Bayesian signal detection theory model to a subset of tasks.
People with PD were worse than controls at object recognition, showing no deficits in other visuo-perceptual tests. Specifically, they were worse at identifying skewed images (P < .0001); at detecting hidden objects (P = .0039); at identifying objects in peripheral vision (P < .0001); and at detecting biological motion (P = .0065). In contrast, people with PD were not worse at mental rotation or subjective size perception. Using signal detection modelling, we found this effect was driven by change in perceptual sensitivity rather than response bias.
Online tests can detect visuo-perceptual deficits in people with PD, with object recognition particularly affected. Ultimately, visuo-perceptual tests may be developed to identify at-risk patients for clinical trials to slow PD dementia. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
This understanding underpins the work presented here by one of our collaborators, Dr Rimona Weil. She has developed online visual tasks which are sensitive to some of these issues. Her 6 tests covered different aspects of visual processing; the test for object invariance, the ability to detect an image despite distortion is shown in the image below. Also tested were peripheral vision, the ability to detect hidden images, to detect biological motion, relative sizes of shapes and mental rotation.
Interestingly, not all the tests differentiated Parkinson's patients from healthy participants. The distorted image was particularly sensitive to detect differences between groups but the results from mental rotation and subjective size perception were similar.
The importance of these findings - that a short online test performed remotely can detect differences between Parkinson's patients and healthy older people - opens up many possibilities. These kinds of tools are likely to find a role in remote monitoring of patients, especially those who find it difficult to attend clinic. Here at PREDICT-PD we are interested in using these tests for screening and will be working with Dr Weil to find out whether any of the changes in visual processing are present before diagnosis of Parkinson's.
-Anna
https://www.ncbi.nlm.nih.gov/pubmed/29473691
Assessing cognitive dysfunction in Parkinson's disease: An online tool to detect visuo-perceptual deficits.
Weil RS, Schwarzkopf DS, Bahrami B, Fleming SM, Jackson BM, Goch TJC, Saygin AP, Miller LE, Pappa K, Pavisic I, Schade RN, Noyce AJ, Crutch SJ, O'Keeffe AG, Schrag AE, Morris HR
BACKGROUND:
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