One of the many annoying consequences of getting older is that driving becomes increasingly difficult.
Seniors behind the wheel can't easily keep track of other cars, pedestrians or cyclists moving around them. And it's not simply a matter of deteriorating eyesight: Their brains also have a harder time focusing on what's visually important.
But a study by a team of researchers at the University of Rochester provides new insights into the aging brain and points to a possible way for seniors to maintain driving skills.
"We started this work knowing from prior research that older adults are better at perceiving large background-like motions. On the other hand, young healthy people perceptually suppress such visual motions," noted Duje Tadin, the lead author of the study published in The Journal of Neuroscience.
"This may sound like a good thing for older adults, but if presented with a highly dynamic visual scene - such as during driving - suppression of often-irrelevant background motions is advantageous. Think of it as eliminating irrelevant information. Basically, this is one more thing that makes driving harder as we age."
Based on earlier experiments, the Rochester researchers had a hunch that a young person's ability to suppress distracting background motion is rooted in a part of the brain known as the middle temporal visual area, or MT for short.
For their study, they decided to temporally de-activate the MT in six healthy young adults using a technique called Transcranial Magnetic Stimulation. (Magnetic coils, precisely placed at the back of the head, sent a mild electric current to the MT and inhibited its function.)
When the MT was briefly out of commission - or "off-line" - the young adults experienced the same visual perceptions as seniors. In other words, they had a harder time ignoring the unimportant motions of background objects.
Dr. Tadin said this study helps to confirm that an "improperly functioning" MT is likely responsible for some of the perception difficulties experienced by seniors while driving.
Knowing this piece of the puzzle may enable researchers to develop new strategies to help seniors cope with their visual limitations, he said.
His team has already begun a trial to see if older adults can be trained to block out extraneous visual data in the background and shift their attention to just the relevant details in the foreground.
"What we are doing now is conducting perceptual learning studies where older adults practice to detect moving objects on moving backgrounds," he explained. So far, the preliminary results look promising with the seniors showing some improvement. "Our hypothesis is that they get better because they get better at suppressing distracting background motion."