Older people get the big pictureFeb 05, 2005; Posted 03:49 am EST (08:49 GMT) 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 researcers 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.
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