For individuals with early stage Alzheimer’s disease, memory problems may be due, in part, to having trouble noticing the differences between similar objects, according to researchers from Georgia Tech and the University of Toronto.
The findings support growing research which suggests that a part of the brain once believed to support memory only — the medial temporal lobe — also plays a role in object perception.
Mild cognitive impairment (MCI) is considered a precursor to Alzheimer’s disease. For the study, researchers asked MCI patients to look at two rotated, side-by-side pictures, and tell if they were different or identical.
In one episode, many photos of the same thing (a blob-like object) were shown. The photos varied only slightly when they weren’t a perfect match, either by shape, color or fill pattern. During these high-interference photos, MCI patients struggled greatly to pinpoint identical objects.
In another episode, the blob-like objects appeared with photos in which non-matches were more extreme and varied widely. For example, a picture of a butterfly was shown next to a photo of a microwave. Mixing the very similar blob-like objects with photos of dissimilar objects greatly reduced the amount of interference.
“Minimizing the degree of perceptual interference improved patients’ object perception by reducing the number of visually similar features,” said project leader Rachel Newsome, a University of Toronto Ph.D. student and Georgia Tech graduate.
The results indicate that, under certain circumstances, reducing “visual clutter” might help MCI patients perform everyday activities.
For example, telephone buttons tend to be the same size and color. Only the numbers are different — a very slight visual difference for a person who struggles with object perception. Perhaps a phone with varying sized buttons and different colors would help.
“Not only does memory seem to be very closely linked to perception, but it’s also likely that one affects the other,” said Toronto’s Morgan Barense, Ph.D. “Alzheimer’s patients may have trouble recognizing a loved one’s face, not only because they can’t remember it, but also because they aren’t able to correctly perceive its distinct combination of features to begin with.”
MCI patients weren’t the only ones who struggled during the study. Individuals at-risk for MCI, people who had previously shown no signs of cognitive impairment, performed about the same as those with MCI.
This suggests that the perception test could be used as an early indicator of cognitive decline.
“People often associate MCI and dementia solely with memory impairment,” said Audrey Duarte, Ph.D., one of the study’s authors. “Memory and perception appear to be intertwined in the same area of the human brain.”
The researchers are among a growing number of others studying Alzheimer’s who believe damage to a small area of the medial temporal lobes, the perirhinal cortex, affects object perception.
The results are published in the October edition of Hippocampus.
Source: Georgia Institute of Technology