3 days ago
Simple, Noninvasive Eye Tracking May Flag Cognitive Decline
Naturalistic gaze patterns appear to be a simple, noninvasive, and reliable indicator of cognitive decline, new research suggested.
Investigators found that gaze patterns during image viewing mirrored memory performance and distinguished healthy adults from those at risk for, or with, cognitive impairment.
'We are still in the early stages of establishing eye tracking as a marker of memory and cognitive status,' lead investigator Jordana S. Wynn, PhD, assistant professor of psychology at the University of Victoria, British Columbia, Canada, told Medscape Medical News .
Although larger, more diverse, and longitudinal research validation is warranted, 'this work lays important groundwork by demonstrating that naturalistic eye movement patterns are meaningfully related to memory function,' she added.
The study was published online on August 11 in the Proceedings of the National Academy of Sciences.
Novel Research
Because the fovea — a small, cone-dense region at the center of the retina — captures high-resolution detail only in the center of the visual field, the eyes must constantly move to sample the full environment.
These movements provide a precise, noninvasive measure of how visual information is encoded and retrieved from memory. While prior research has linked certain gaze metrics to memory decline, it remains unclear how multivariate gaze patterns — considering multiple eye movement features together — relate to memory function.
For the study, which researchers note is the first work to analyze how eye movements differ across a range of brain health and memory function levels, Wynn and colleagues assessed 106 individuals across five groups — young adults, healthy older adults, individuals at risk for significant cognitive decline, those with mild cognitive impairment (MCI), and those with amnesia.
They hypothesized that changes in gaze patterns would correspond in a linear fashion to cognitive function from the healthiest participants to those with amnesia.
The study included two experiments. In the first, participants viewed a series of 120 distinct images, each for 5 seconds, to assess 'idiosyncratic gaze similarity,' or the uniqueness of their viewing patterns. As expected, memory function declined across groups — from young adults to healthy older adults, then to the at-risk group, followed by individuals with MCI and those with amnesia, showing a 'meaningful linear relationship.'
In the second experiment, investigators used the same set of images, presenting 60 images once and another 60 three times for 5 seconds each to measure 'repetitive gaze similarity.' This approach revealed whether participants consistently encoded the same image features each time on repeat viewings or if they updated their memory with different features, indicating stronger or more flexible memory encoding.
The researchers found that the healthy young adult group encoded unique image features with each image presentation. In contrast, participants with decreased memory and/or hippocampal/medial temporal function tended to focus on the same features each time they saw the same image.
These results confirm that memory decline is associated with reduced visual exploration, less effective updating of encoded representations over repeated exposures, and lower differentiation of the images.
Exciting, but Not Surprising
Wynn said she was not particularly surprised by the study findings. 'Our previous work in healthy populations provided evidence that the brain and cognitive systems supporting eye movements and memory are closely linked. In past experimental work, we found that certain gaze patterns were predictive of memory performance,' she said.
Therefore, Wynn and colleagues postulated that memory decline from aging, disease, or injury would yield similar changes in eye movements.
'That our prediction was confirmed was certainly exciting, but not surprising,' she added.
The investigators concluded that the results provide 'compelling evidence that naturalistic gaze patterns can serve as a sensitive marker of cognitive decline.'
This research lays a foundation for future work using multivariate gaze metrics to diagnose and track memory and/or hippocampal/medial temporal lobe function, they added.
It's too early to determine whether naturalistic eye movements could become a first-line screening tool for cognitive decline, Wynn said.
'The value of eye tracking compared to standard neuropsychological tests is that it is noninvasive, cost-effective, and perhaps most importantly, universal,' she noted. Nearly anyone — regardless of age, ability, or language — can view pictures on a screen, so creating a screening tool that doesn't rely on written or verbal responses would be particularly practical, Wynn said.
It is still too early to know whether naturalistic eye movements could serve as a first-line screening tool for cognitive decline. Wynn noted that eye tracking is noninvasive, cost-effective, and broadly accessible — anyone, regardless of age, ability, or language, can view images on a screen. With further refinement, she said, these measures could provide a high-resolution way to monitor memory and brain function in clinical settings.
Novel Insights
Commenting on the research for Medscape Medical News , Mariam Aly, PhD, acting associate professor of psychology at the University of California, Berkeley, said the study 'yields novel insights into how the way people move their eyes can contribute to, and reflect, memory impairments.'
'This elegant study uses sophisticated analyses to provide a comprehensive picture of how eye movement patterns differ across groups that span a continuum of memory abilities.'
Importantly, these differences in eye movements were apparent even though participants had no explicit task, added Aly, who was not affiliated with the research.
'This means that assessment of eye movements during natural viewing of images has the potential to be developed into an important tool for detecting memory decline in clinical settings,' she said.
