Young kids can pick up a new language or learn a musical instrument in a flash compared to us old-timers. It seems the older we get, the worse our auditory learning becomes.
Scientists have now identified a key chemical messenger in the brain of mice that may slow down this type of learning. By playing around with this chemical, the researchers now think they can manipulate it and extend the mice's – and perhaps one day our – window to learn new sounds, which could impact language and musical acquisition. The new study is published in the journal Science.
By either reducing levels of adenosine or blocking the A1 receptor in the auditory thalamus, the team found that adult mice had significantly better auditory learning skills.
This part of the brain is where sounds are “collected” before being sent to the auditory cortex for processing. The researchers found that the experimental compound, known as “FR194921”, blocks the A1 receptor, thereby inhibiting the effect of adenosine.
"By disrupting adenosine signaling in the auditory thalamus, we have extended the window for auditory learning for the longest period yet reported, well into adulthood and far beyond the usual critical period in mice," study author Stanislav Zakharenko, a member from St Jude Department of Developmental Neurobiology, said in a statement. "These results offer a promising strategy to extend the same window in humans to acquire language or musical ability by restoring plasticity in critical regions of the brain, possibly by developing drugs that selectively block adenosine activity."
In one demonstration, the mice improved in their ability to distinguish between tones with slightly different frequencies. Another showed that months later the mice were able to remember tones they were trained to respond to.
“Taken together, the results demonstrated that the window for effective auditory learning re-opened in the mice and that they retained the information," Zakharenko said.
As we age, our levels of an enzyme called ecto-5'-nucleotidase increase. This enzyme has been shown by the scientists to be involved in the production of adenosine. They're now on the hunt for compounds that target this enzyme, thereby dropping adenosine levels and extending the window of auditory learning.
This could have implications for humans, but it is much too early to say for certain. Questions have been raised by neuroscientist Jennifer Linden, who was involved in the study, in Scientific American.
The study's researchers, for their part, say it could inspire treatments for tinnitus and people recovering from strokes. Perhaps one day, it could even be used to extend this “juvenile plasticity" window, and give us greater time to learn instruments and pick up languages as quickly as a child.