Why it's hard to learn new things as we get older
Why does our capacity to pick up skills like playing instruments or learning languages, to remember where we put our keys and a thousand other things, get poorer and poorer as we age? A study just published in the Journal of Neuroscience suggests that one crucial reason is the loss of certain structures in brain cells called "spines."
The authors, at the Mt. Sinai School of Medicine, looked at two groups of rhesus monkeys: young adults and elderly adults. First they tested the animals' ability to quickly learn where some food was hidden -- and, not surprisingly, found the young monkeys were a lot better at the task than the old ones, especially when they had to retain the memory of where the food was hidden for a longer period of time. Then the scientists examined nerve cells in each group in a part of the brain called the prefrontal cortex, important for learning and memory.
They found that numbers of spines -- tiny spiky projections on the nerves that make connections with other nerves -- were greatly reduced in the older brains. Specifically, the number of thin spines, which change rapidly and are actively involved in learning new things, were reduced. Fatter spines that seem to be more involved in retaining old memories weren't affected -- the first time to the authors' knowledge that this has ever been demonstrated.
What goes for rhesus monkeys very probably goes for what happens during normal human aging, the authors added -- and so this finding could explain (at least in part) why we're able to remember events and skills we learned long ago but become poorer and poorer at setting down new memories and developing new skills as we grow older.
"The bad news may be that we can't make an old dog learn new tricks," they conclude. "The good news, however, is that we can age gracefully by emphasizing learning in our youth."
-- Rosie Mestel
Photo: Skills like playing the violin become a heck of a lot tougher to pick up as we get older -- perhaps because our brain cells don't readily form new "spikes."
Credit: Ricardo DeAratanha / Los Angeles Times