Study: Alzheimer's Patients Develop "Motion Blindness"

Alzheimer's disease patients are subject to a unique form of brain damage that causes "motion blindness," according to researchers at the University of Rochester Medical Center.

The condition can be assessed by looking at a person's loss of ability to stay in one lane while driving a car.

"While it's obvious that people with Alzheimer's disease are losing their memory, that's only part of the reason why they become lost," said Dr. Charles Duffy, neurologist and lead researcher. "These patients also lose their ability to perceive their own motion. That's ultimately what puts them at much greater risk than others of becoming lost."

Researchers studied 26 elderly patients with Alzheimer's disease, 50 healthy elderly adults, and 32 healthy young adults. The participants were evaluated for vision and their ability to perceive motion.

The Alzheimer's patients who were still driving were given a standard New York State driver's test. As expected, older patients had more difficulty with memory than the younger patients and among the older patients, the group with Alzheimer's had a harder time detecting motion than the healthy group, according to the researchers.

The 11 Alzheimer's patients who were still driving performed adequately on all areas of the test except the portion that measures their own knowledge of their location on the road. These patients tended to drift out of their lane, either across the middle or to the right, and they had a hard time knowing how close or far away they were from the car ahead of them, according to the study published in the journal Cerebral Cortex.

"These people weren't just bad drivers. They were bad drivers in a particular way," said Duffy. "They couldn't judge where they were in their lane, which mirrors what we've found in the laboratory."

"Losing the right to drive is a tremendous burden; it inflicts further hardship on people who are already having a very difficult time," said Duffy. "If we can understand who is really at risk for having difficulty driving, and for getting lost -- if the disease didn't mean the kind of loss of independence it now means for most people -- that would be significant. It's crucial not to be arbitrary."

Duffy first reported the condition of motion blindness three years ago when he discovered that many Alzheimer's patients had a harder time detecting motion as they move in the world.

Other sources: University of Rochester Medical Center