Taylor Schmitz is a PhD student in U of T’s Collaborative Program in Neuroscience, and conducts studies at the intersection of neuroscience and psychology. By measuring activation in the visual cortex in his most recent experiment, he tested both younger and older adults’ ability to focus on pictures and select relevant information from them.
Schmitz assembled a group of 15 healthy young adults with a mean age of 22.2 years, along with a group of 15 healthy older adults averaging 77.4 years of age. Before conducting the experiment, Schmitz chose to observe two specific parts of the brain: the parahippocampal place area, or PPA, which responds to images of houses and buildings; and the fusiform face area, or FFA, which responds to faces.
Although 15 individuals in each group may not seem like a very large sample size, Schmitz assures that “the brain regions being studied do not differ significantly from one individual to the next. Some studies make the mistake of generalizing specific findings, but this does not concern us, because of the brain regions that we chose to study.”
Schmitz selected photographs of expressionless faces from a “psychological and computer-recognition database,” and cropped all hair and non-facial features from each picture. He then obtained images of houses from real estate websites.
In the “adaption” task, participants were placed in an fMRI scanner, and were asked to identify whether each face that was presented was female or male. Results showed that the older group generally made more errors when identifying male and female faces. PPA activation was significantly greater for the young adults, and overall FFA activation tended to be greater in the younger group as well.
In the second part of the experiment, both groups were asked to look at a picture of a 50 per cent transparency face that had been superimposed on a picture of a house. Researchers asked participants to focus only on the face, and identify its gender.
The fact that the PPA was activated in the older adults during this task showed that they were encoding both the face and the location, despite being asked to focus only on the face. In contrast, younger adults did not encode the locations at all but only encoded the faces, showing activation in the FFA only. Ten minutes after the study was conducted, the older adults also still remembered the places that corresponded to each face.
“Our brain-behaviour results suggest the intriguing possibility that a reduced discriminatory signal originating from receptive field push-pull mechanisms might underlie age-related declines in perceptual attention,” Schmitz mentions in his study.
Schmitz concludes that younger adults possess a perceptual filter that can separate out unwanted information, while only focusing on what is relevant. On the other hand, older adults have a “leaky” perceptual filter, which means they tend to process more irrelevant information.
However, Schmitz has yet to understand what precisely occurs at a neural level to make the filter “leaky.” Further experimental work will also include altering the perceptual load — in other words, varying the opacity of the pictures — in order to see how each group responds to the stimuli under different conditions.
At present, Schmitz is focused on expanding his current findings by altering the images and observing the brain changes that occur in each age group, in order to fully prove that older adults are more vulnerable to distraction.
