Learning becomes harder as we get older due to a reduced ability to filter out old memories, according to new international research.
In the brain, the hippocampus contains a “switch” called the NMDA receptor that optimizes learning and memory, expressing either NR2A or NR2B. The latter is found in larger amounts in children, allowing their neurons to work slightly longer, and form stronger links or synapses. After puberty, this ratio changes and more NR2A is produced.
“When you are young, your brain is able to strengthen certain connections and weaken certain connections to make new memories,” said study co-author Dr. Joe Z. Tsien at Georgia Regents University in a press release.
“If you only make synapses stronger and never get rid of the noise or less useful information, then it’s a problem.”
Tsien’s team studied genetically modified mice with more NR2A and less NR2B, i.e. the ratio found in human adults. The mice still formed strong synapses and short-term memories, but their ability to sculpt information was lower; they were less able to weaken synapses and make new long-term memories.
“What is abnormal is the ability to weaken existing connectivity,” Tsien noted.
This change in the adult brain could contribute to the phenomenon often seen in older people who can be stuck in their ways, and also adults who cannot get rid of their accent while learning a new language.
“We know we lose the ability to perfectly speak a foreign language if we learn that language after the onset of sexual maturity,” Tsien said. “I can learn English but my Chinese accent is very difficult to get rid of.”
“The question is why.”
The research was published in Scientific Reports on Jan. 8.
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