neurosciencestuff:

New insight into aging

They say you can’t teach old dogs new tricks, but new research shows
you can teach an old rat new sounds, even if the lesson doesn’t stick
very long.

Researchers at the Montreal Neurological Institute and Hospital (The
Neuro) of McGill University examined the effects of aging on
neuroplasticity in the primary auditory cortex, the part of the brain
that processes auditory information. Neuroplasticity refers to the
brain’s ability to modify its connections and function in response to
environmental demands, an important process in learning.

Plasticity in the young brain is very strong as we learn to map our
surroundings using the senses. As we grow older, plasticity decreases to
stabilize what we have already learned. This stabilization is partly
controlled by a neurotransmitter called gamma-Aminobutyric acid (GABA), which inhibits neuronal activity. This role of GABA was discovered by K.A.C. Elliot and Ernst Florey at The Neuro in 1956.

First author Dr. Mike Cisneros-Franco and lab director Dr. Étienne de
Villers-Sidani wanted to test the hypothesis that plasticity
stabilization processes become dysregulated as we age. They ran an
experiment where rats were exposed to audio tones of a specific
frequency to measure how neurons in the primary auditory cortex adapt
their responses to the tones. They found that tone exposure caused
neurons in older adult rats to become increasingly sensitized to the
frequency, but this did not happen in younger adult rats. The effect in
the older adult rats quickly disappeared after exposure, showing that
plasticity was indeed dysregulated. However, by increasing the levels of
the GABA neurotransmitter in another group of older rats, the
exposure-induced plastic changes in the auditory cortex lasted longer.

These findings suggest the brain’s ability to adapt its functional
properties does not disappear as we age. Rather, they provide evidence
that plasticity is, in fact, increased but dysregulated in the aged
brain because of reduced GABA levels. Overall, the findings suggest that
increasing GABA levels may improve the retention of learning in the
aging brain.

“Our work showed that the aging brain is, contrary to a widely-held
notion, more plastic than the young adult brain,” says Cisneros-Franco.
“On the flip side, this increased plasticity meant that any changes
achieved through stimulation or training were unstable: both easy to
achieve and easy to reverse.”

“However, we also showed that it is possible to reduce this
instability using clinically available drugs. Researchers and clinicians
may build upon this knowledge to develop rehabilitation strategies to
harness the full plastic potential of the aging brain.”

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