The dementia associated with Parkinson’s disease could be diagnosed earlier with new visual tests developed by University of Queensland researchers.
Neurologist Professor Peter Nestor from UQ’s Queensland Brain Institute and Mater Hospital Brisbane’s Memory and Cognitive Disorders Clinic, led the development of the tests to detect early signs of dementia in Lewy body disease, which includes Parkinson’s disease and dementia with Lewy bodies.
“Difficulty in the brain’s ability to process visual information is an early feature of Lewy body disease and can appear before any other obvious symptoms of dementia,’’ Professor Nestor said.
“We haven’t invented the idea of testing how the brain processes visual information; but existing tests were often too simple, rendering them incapable of detecting mild, early deficits.’’
Lewy body disease is the second most common form of degenerative dementia and occurs when Lewy bodies - abnormal clumps of a protein called alpha-synuclein - build up in the brain’s nerve cells and interfere with how they work.
It can manifest in different ways: as a movement disorder, that is referred to clinically as Parkinson’s disease; or as a disorder of cognitive abilities, that is labelled clinically as dementia with Lewy bodies.
In the UQ-led study, researchers worked with 53 people with Lewy body disease and 29 people with Alzheimer’s disease who were recruited from Professor Nestor’s clinic and the Movement Disorder Clinic of neurologist Associate Professor John O’Sullivan from UQ’s Frazer Institute .
Study lead author Dr Emily McCann , who conducted the research as part of her PhD at the Queensland Brain Institute, said this allowed the full spectrum of Lewy body disease to be examined, including people with Parkinson’s disease who were not experiencing any cognitive symptoms.
“The study examined the 2 visual streams used by the brain to process what we see with our eyes: the ventral stream allows us to recognise what we are looking at, such as the face of a loved one; and the dorsal stream which processes where something is located, such as finding an object in a busy room,” Dr McCann said.
To test the ventral stream, participants were asked to complete a Graded Blurry Image test, identifying a series of objects that started blurred beyond recognition but gradually became clearer.
The dorsal stream was examined by identifying numbers (from zero to 9) ‘hidden’ in a series of images of disordered black dots and background noise.
“Rather than take a positive image and degrade it, the number was formed from the absence of background noise, meaning the brain had to fill in the missing information to solve the test,’’ Dr McCann said.
Results showed visual problems were worse for those with Lewy body disease than Alzheimer’s disease, and that the 2 visual processing pathways were affected differently for the 2 diseases.
Visual hallucinations, a common symptom of Lewy body disease, were also closely linked to visual processing difficulties.
Professor Nestor said the tests were designed to be sensitive to the earliest signs of impairment and would also allow clinicians to track change in people over time.
“Building gradations of difficulty into the tests means that even healthy people cannot score perfectly,’’ he said.
“Our results show these new tests can detect the very earliest signs of emerging dementia in Lewy body disease, including some people with Parkinson’s disease who were not yet aware that they were beginning to develop problems with visual information processing.
“In my experience, giving people accurate information and a clear diagnosis for the symptoms they are experiencing, or are going to experience, enables them to cope better with the situation they find themselves in.
“When people are held in limbo, where they are developing symptoms of a degenerative brain disease and no one can give them a clear answer, they can experience significant distress, as do their families.’’
Read the research in Journal of Neurology .
Collaborations and acknowledgements:
The research was conducted with the support of the Mater Foundation.
Media: UQ Communications, communications@uq.edu.au , +61 429 056 139.
Journal of Neurology
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Dorsal and ventral stream visuoperceptual processing deficits in Lewy body disease
25-Sep-2026