Scientists have identified a key chemical messenger in the brain that slows down learning such as language or music in adults.

The study, conducted on mice, showed that limiting the supply or the function of a chemical, adenosine, in a brain structure known as the auditory thalamus -- brain's relay station where sound is collected -- could preserve the ability of adult mice to learn from passive exposure to sound much as young children learn from the soundscape of their world.Much as young children pick up language simply by hearing it spoken, when adenosine was reduced or the A1 receptor blocked in the auditory thalamus, the adult mice responded to the tone much stronger when it was played weeks or months later than before.

The findings could lead to new drugs to turn off this chemical so learning becomes a breeze, the researchers said, in the paper appearing in the journal Science."By disrupting adenosine signalling 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," said Stanislav Zakharenko, from the St. Jude Children's Research Hospital in Tennessee, US.These adult mice also gained an ability to distinguish between very close tones (or tones with similar frequencies), an ability they usually lack."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," Zakharenko said.