When we are young, our brain can strengthen certain connections and weaken other connections to make new memories, says Dr. Joe Z. Tsien, neuroscientist at the Medical College of Georgia at Georgia Regents University and Co-Director of the GRU Brain & Behavior Discovery Institute. It's that weakening that appears suffer as the brain ages, according to a study published in the journal Scientific Reports.
When Tsien and his colleagues genetically modified mice to mimic old age, they were amazed to discover that the rodents were still able to make strong connections and short-term memories but could not weaken existing connections effectively, [called long-term depression] It's also called information sculpting and as the mice aged they seem appear to get worse at it.
"If you only make synapses stronger and never get rid of the noise or less useful information then it's a problem," said Tsien, the study's corresponding author. While each neuron averages 3,000 synapses, the continuous barrage of information and experiences should ideally result in some selective whittling. Insufficient sculpting, at least in the mouse, was observed with apparent effects on memory.
This impaired ability to trash away unnecessary information could also help explain why adults can't learn a new language without their old accent and why older people tend to be more stuck in their ways, the memory researcher said.
"We know we lose the ability to perfectly speak a foreign language if we learn than language after the onset of sexual maturity. I can learn English but my Chinese accent is very difficult to get rid of. The question is why," Tsien said.
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