Aging process improves certain abilities 

Psychologists from McMaster University have discovered that the aging process improves certain abilities -- the ability to grasp the 'big picture'. The study, published in the journal Neuron dispels the myth that older people perform slower and worse than younger people.

"Going into the study, we knew that ageing changes the way people see the world," says Allison Sekuler, one senior author of the study. "But these results are an unusual twist on the standard 'ageing makes you worse' story, and they provide clear insight into what is changing in the ageing brain."

The researchers measured how long it took for study participants to indicate which direction a set of bars moved across a computer screen. Younger participants were faster when the bars were small or low in contrast. When the bars were large and high in contrast, however, the older people were faster.

"The results are exciting not only because they show an odd case in which older people have better vision than younger people, but also because it may tell us something about how ageing affects the way signals are processed in the brain" says Patrick Bennett, the other senior author.

According to the researchers, the results suggest that the ability of one neuron to inhibit another is reduced as we age. Inhibition helps younger individuals find objects within clutter, but this makes it hard to see the clutter itself. The large, high-contrast bars are 'tuned out' because there is nothing hidden within the bars. Older brains, on the other hand, do not 'tune out' the bars so they can perform the task faster.

"As we get older, it becomes harder to concentrate on one thing and ignore everything else," says Bennett. "It takes more effort to tune out distractions. We've seen it in cognition and speech studies, and now we see it in vision. Although we don't know if those are all linked, we think the visual effect is due to changes in the effectiveness of inhibitory neurotransmitters in the brain."

Neurotransmitters are chemicals in the brain that regulate how neurons communicate with each other -- some enhance brain activity and others inhibit it.

The study suggests that one type of inhibitory neurotransmitter may not have as great an effect in older people as in younger ones. However this also leads to decreased performance on some tasks.

"It's critical to understand how ageing affects vision and the brain. If we can characterize what is happening to our brains as we age, we'll be in a better position to help seniors see better for longer," says Sekuler.

Elderly Eyes Vs. Young

The study involved eight younger volunteers (averaging 23 years old) and eight elderly people (averaging 68 years old). In a series of computer-generated images, the appearance of a set of bars changed while volunteers watched. The bars first appeared small, then larger, low-contrast (light gray vs. dark gray), and high-contrast (black vs. white).

Each volunteer was asked to determine the direction in which the bars moved. Researchers monitored the time it took for them to decide.

Younger volunteers took less time when the bars were small, or when the bars were low in contrast (light gray vs. dark gray).

Elderly volunteers did better when the bars were large, and high in contrast (black vs. white).

"The results are exciting not only because they show an odd case in which older people have better vision than younger people, but also because it may tell us something about how aging affects the way signals are processed in the brain," says Bennett, in a news release.

His study indicates that, as we age, the ability of one brain cell to inhibit another is reduced, Bennett writes. That sort of inhibition helps young people find an object hidden among clutter. But it can make it hard to tune into the clutter itself.

Normally, low-contrast objects require briefer periods of presentation to discriminate the direction of motion as an object size increases. Meanwhile, high contrasting objects normally require longer presentations to discriminate motion.

When the young brain sees big, high-contrast objects (the bars), it effectively tunes out the rest of the picture. It does so through nerve pathways that help inhibit other signals. But older brains do not inhibit information in the same way. Therefore, the older brain requires less time to discriminate motion patterns — and actually performs the task better.

"As we get older, it becomes harder to concentrate on one thing and ignore everything else," says Bennett. "It takes more effort to tune out distractions. We've seen it in [brain function] and speech studies, and now we see it in vision."

Although it's not clear if those factors are all linked, performance changes in elderly people may be due to brain cells' ability to affect other brain cells. Some brain cells enhance brain signals while others inhibit them.

Sources: News release, McMaster University. Betts, L. Neuron, Feb. 2, 2005: vol 45.