Measuring pupils to chart brain health
Using pupil dynamics to assess cognitive functions in healthy aging and clinical populations
Whenever we make a decision, pay attention to a detail, or use our working memory, our pupils change size. That’s because pupil size reflects activities occurring in our brain.
At Queen’s University in Kingston, ON, PhD candidate Po Yueh (Jeff) Huang and his colleagues in the laboratory of Prof. Douglas Munoz measure the relationship between pupil size and people’s decision-making, cognitive flexibility, and planning.
By tracking people’s pupil size while they perform tasks that require mental preparation, Huang and his colleagues are developing a diagnostic test to identify people with neurodegenerative illnesses.
“We want to be able to use eye tracking to look at someone’s eye when they are doing a cognitive task and be able to tell if they have any cognitive deficits, or are at risk of developing diseases such as Parkinson’s or Alzheimer’s,” Huang says.
During his research, Huang measures pupil size as people watch a screen, glancing either towards or away from a visual target.
In healthy people, there is a difference in the size of their pupils as they perform each task. Looking away from the target requires them to engage their brain’s frontal lobe—an area affected by Parkinson’s disease—to prepare for the job.
In people with Parkinson’s, there is less difference in the size of their pupils when they look straight at the target or away from it, reflecting deficits in the underlying neural processes.
“Their performance is worse as well,” Huang explains. “The brain needs to prepare to look away from the target, but their ability to do so is impaired.”
By measuring pupil size against the performance of people with different kinds of neurodegenerative diseases, Huang is also creating a database of measurements that may be useful as early indicators and risk factors of diseases associated with dementia: Parkinson’s, Alzheimer’s, frontal temporal degeneration, vascular dementia and Amyotrophic Lateral Sclerosis (ALS).
Eventually, pupil measurements could be combined with genetic and imaging tests to create a set of markers that could help to diagnose Parkinson’s and other progressive brain disorders earlier.
An early diagnosis could be vital for people with Parkinson’s if there are new drugs or therapies developed to slow or stop the disease’s progression.
Huang’s father, who is an ophthalmologist in Taiwan, and his grandfather, who had Parkinson’s disease, both influenced Huang’s decision to become a neuroscientist.
When he first heard about Munoz’s work on the eye as it relates to neurodegeneration, Huang was hooked. He found it to be the perfect intersection of his interests. Huang hopes his work will contribute to improving the lives of people with Parkinson’s.