Give a dog a treat, and she just might learn that new trick. Could the same concept also help a human recover from a brain injury, or become a violin virtuoso?
Rewards, especially in combination with drugs that enhance the neurotransmitter dopamine, may boost both cognitive and tactile learning, according to research published today in the journal PLoS Biology.
“We have known a lot about reward mechanisms,” says Burkhard Pleger of the Max Planck Institute for Human Cognitive and Brain Sciences and lead author on the study, “but it was not well known how rewards influence sensory processing.”
Researchers designed a game to elucidate this process. Prior to each set of four consecutive trials, Pleger and his colleagues showed participants how much reward could potentially be earned (incentives ranged from zero to 80 pennies). Subjects then attempted to distinguish which of two electric currents applied to their index fingers carried a higher frequency. If they were correct, the visual monetary reward was displayed.
The higher the reward, Pleger and his colleagues found, the more correct decisions were made on subsequent trials. Subjects appeared to be learning. “They always had the carrot in front of their eyes,” says Pleger. A feedback between the sensory and reward centers, he explains, “optimized brain functions to get the highest possible reward.”
Evidence of a “dopaminergic dependency” also arose in the experiment, Pleger said. Researchers randomly assigned each subject to one of three groups. Learning improved the most for those receiving a drug that raised dopamine levels, and less so for those on a placebo. Subjects who took a dopamine inhibitor showed the least improvement in sensory discrimination.
Potential applications of insights from these findings could range from music to medicine. “Let’s say you want to learn to play a string instrument,” says Pleger. “You don’t just need motor skills; you also need sensory skills. Such a drug could be of interest.” He cautions, however, that dopamine could be “quite dangerous” in “higher doses,” noting a link between raised levels of the neurotransmitter and mental illnesses such as schizophrenia.
The most important use of this research, Pleger suggests, may be in brain trauma or stroke rehabilitation—as long as a doctor controls administration of the pharmaceuticals, of course. “You could use reward in combination with dopamine to boost therapeutic effects,” notes Pleger. “This could be really helpful.”
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