The saying, “looking at things with fresh eyes”, may be more than just a metaphor, according to new studies led by Professor Kari Hoffman of York’s Centre for Vision Research, which have been published in scholarly journals.
Left: Kari Hoffman
While searching for experiments to use in a research methods course, Hoffman took a fresh look at an old visual perception test and realized it might hold a clue to understanding how we see things and when we remember them. Hoffman says the insight came when she was reviewing results of a flicker-change blindness test, a simple classroom experiment used to show how difficult it is for people to see the difference in two almost identical images or scenes. She realized that what was once a trick of the eye was no longer effective due to her memory of the images.
That led Hoffman and biology graduate student Vivian Chau (right) to develop an experiment that would monitor the eye movement of test subjects as they tried to solve the visual puzzle. What they found was striking: when the viewer remembered the image, the eye movement that indicated the time it took to search and locate the part of the scene that had changed was dramatically reduced compared to when they were viewing it for the first time. This suggested that it was possible to tell when a person was looking at an image for the first time and when they recognized it from memory.
“Not everyone shows the fast search times, though,” says Hoffman. “A participant with amnesia failed to remember the changing objects and his eyes told the story. This participant had suffered damage to his medial temporal lobe, a region which is especially affected in Alzheimer's patients and has been associated with memory function in healthy aging,” said Hoffman. “So we now have a task to help us study how that brain region functions to support memory formation.”
The study results were published in Frontiers in Behavioral Neuroscience (Sept. 20, 2011).
After seeing that eye movements could reflect memory, the outcome of brain processing, Hoffman and her lab team wondered if eye movements might also take part in influencing the inputs – how our brain processes images. In a second study, she and psychology graduate student Adrian Bartlett (right) found that eye movement is also an indication of the brain gearing up to process an image – a kind of neural “smart refresh” that created optimal conditions for seeing.
Hoffman says there is a noticeable change in a subject’s brain wave patterns when images are viewed with moving eyes as opposed to the more standard experimental method of viewing images with a fixed eye. “The neural populations become more synchronized,” she explains, “this can make processing an image easier and faster.” They found that the brain has a kind of “smart refresh” period when it gets ready to process visual information. If the presentation isn’t synched to that cycle, the brain is not as good at processing the image.
Designers of learning materials can use this knowledge to create visual presentations that interact with a viewer’s movements, making the displays more easily processed and therefore more effective. The study was published in the Journal of Neuroscience (Dec. 14, 2011).
Illustration above shows the path the viewer's eyes followed when scanning the photo for the first time and then again the next day
“Although scientists often study movement as a separate process from perception and cognition,” Hoffman says, “our results reveal examples of how eye movements are intertwined with perceptual and cognitive processes. In both studies, the eye movements give us a more complete picture of perceptual and memory processes,” Hoffman explains.
Exercising the brain in this way, Hoffman says, may be optimal for neural rewiring or "plasticity" that leads to better learning, more efficient performance and recovery after loss of function, such as following stroke. “This provides support for a more integrative view of brain function – one in which actions help shape brain performance.”
For more information on the Perception & Plasticity Lab, visit their website.
The studies, which were conducted in collaboration with researchers Jennifer Ryan, Shayna Rosenbaum and Nikos Logothetis, were funded through an NSERC Discovery Grant and an Ontario MRI Early Researcher Award. Hoffman is a professor in psychology & biology in York's Faculty of Health and a member of the Neuroscience Graduate Diploma Program.