Eliminating useless information important to learning, making new memories

January 9, 2013
As we age, it just may be the ability to filter and eliminate old information -- rather than take in the new stuff -- that makes it harder to learn, according to Dr. Joe Tsien, Medical College of Georgia at Georgia Regents University, neuroscientist and Co-Director of the GRU Brain & Behavior Discovery Institute. Credit: Phil Jones, Georgia Regents University, Campus Photographer

As we age, it just may be the ability to filter and eliminate old information – rather than take in the new stuff - that makes it harder to learn, scientists report.

"When you are young, your brain is able to strengthen certain connections and weaken certain connections to make new memories," said 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 critical weakening that appears hampered in the older brain, according to a study in the journal Scientific Reports.

The NMDA receptor in the 's hippocampus is like a switch for regulating learning and memory, working through subunits called NR2A and NR2B. NR2B is expressed in higher percentages in children, enabling neurons to talk a fraction of a second longer; make stronger bonds, called synapses; and optimize and memory. This formation of strong bonds is called long-term potentiation. The ratio shifts after puberty, so there is more NR2A and slightly reduced communication time between neurons.

When Tsien and his colleagues genetically modified mice that mimic the adult ratio – more NR2A, less NR2B – they were surprised to find the rodents were still good at making strong connections and short-term memories but had an impaired ability to weaken existing connections, called long-term depression, and to make new long-term memories as a result. It's called information sculpting and adult ratios of NMDA receptor subunits don't appear to be very good 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 relentless onslaught of information and experiences necessitates some selective whittling. Insufficient sculpting, at least in their mouse, meant a reduced ability to remember things short-term – like the ticket number at a fast-food restaurant – and long-term – like remembering a favorite menu item at that restaurant. Both are impacted in Alzheimer's and age-related dementia.

All long-term depression was not lost in the mice, rather just response to the specific electrical stimulation levels that should induce weakening of the synapse. Tsien expected to find the opposite: that long-term potentiation was weak and so was the ability to learn and make . "What is abnormal is the ability to weaken existing connectivity."

Acknowledging the leap, this impaired ability 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.

Tsien and his colleagues already have learned what happens when NR2B is overexpressed. He and East China Normal University researchers announced in 2009 the development of Hobbie-J, a smarter than average rat. A decade earlier, Tsien reported in the journal Nature the development of a smart mouse dubbed Doogie using the same techniques to over-express the NR2B gene in the hippocampus.

Doogie, Hobbie-J and their descendants have maintained superior memory as they age. Now Tsien is interested in following the NR2A over-expressing mouse to see what happens.

Explore further: Habit formation is enabled by gateway to brain cells

Related Stories

Habit formation is enabled by gateway to brain cells

December 21, 2011
A brain cell type found where habits are formed and movement is controlled has receptors that work like computer processors to translate regular activities into habits, researchers report.

New target for Alzheimer's drugs

February 9, 2012
(Medical Xpress) -- Biomedical scientists at the University of California, Riverside have identified a new link between a protein called beta-arrestin and short-term memory that could open new doors for the therapeutic treatment ...

Recommended for you

Researchers find monkey brain structure that decides if viewed objects are new or unidentified

August 18, 2017
A team of researchers working at the University of Tokyo School of Medicine has found what they believe is the part of the monkey brain that decides if something that is being viewed is recognizable. In their paper published ...

Artificial neural networks decode brain activity during performed and imagined movements

August 18, 2017
Artificial intelligence has far outpaced human intelligence in certain tasks. Several groups from the Freiburg excellence cluster BrainLinks-BrainTools led by neuroscientist private lecturer Dr. Tonio Ball are showing how ...

Study of nervous system cells can help to understand degenerative diseases

August 18, 2017
The results of a new study show that many of the genes expressed by microglia differ between humans and mice, which are frequently used as animal models in research on Alzheimer's disease and other neurodegenerative disorders.

How whip-like cell appendages promote bodily fluid flow

August 18, 2017
Researchers at Nagoya University have identified a molecule that enables cell appendages called cilia to beat in a coordinated way to drive the flow of fluid around the brain; this prevents the accumulation of this fluid, ...

Researchers make surprising discovery about how neurons talk to each other

August 17, 2017
Researchers at the University of Pittsburgh have uncovered the mechanism by which neurons keep up with the demands of repeatedly sending signals to other neurons. The new findings, made in fruit flies and mice, challenge ...

Neurons involved in learning, memory preservation less stable, more flexible than once thought

August 17, 2017
The human brain has a region of cells responsible for linking sensory cues to actions and behaviors and cataloging the link as a memory. Cells that form these links have been deemed highly stable and fixed.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Tausch
not rated yet Jan 09, 2013
Comedian Harmonists
The Revelers

A melody replaces your accent when 'speaking'(singing) the songs' text/lyrics.
The question is why.

Answering your question of why:

I can learn English but my Chinese accent is very difficult to get rid of. The question is why," Tsien said.


What sounds are overriding(?) the sounds of normal conversational pronunciation?

How is 'connectivity' being 'outwitted'?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.