The long-held belief that older people perform slower and worse
than younger people has been proven wrong. In a study published
today in Neuron, psychologists from McMaster University discovered
that the ageing process actually improves certain abilities: Older
people appear to be better and faster at grasping the big picture
than their younger counterparts.
"Going into the study, we knew that ageing changes the way people
see the world," says Allison Sekuler, one of the senior authors
and a Canada Research Chair at McMaster. "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
Using computer-generated stimuli, the researchers monitored how
much time subjects needed to process information about the direction
in which a set of bars moved. When the bars were small, or when
the bars were low in contrast (light gray vs. dark gray), younger
subjects took less time to see the direction of motion. But when
the bars were large, and high in contrast (black vs. white), older
subjects outperformed the younger subjects.
"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, also a Canada Research Chair at McMaster.
The results suggest that as we age, the ability of one brain cell
to inhibit another is reduced. 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. When the young brain sees big,
high-contrast bars, it effectively tunes out because there is no
object hidden in the bars. But older brains do not inhibit information
in the same way, so they do not tune out the bars, and they can
actually perform 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 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 chemical substances that can modify the way
in which brain cells talk to one another. Some neurotransmitters
enhance brain signals, and others inhibit them.
The study, conducted in collaboration with PhD students Lisa Betts
and Christopher Taylor, suggests that one type of inhibitory neurotransmitter
may not have as much effect in old brains as in young brains. However,
the researchers caution that although such a change makes older
people perform better on this task, the same change likely leads
to increased difficulties in a much wider range of 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," say
Reference Source 131