Laboratory monkeys that had been careless procrastinators became super-efficient workers after injections into their brains that suppressed a gene linked to their ability to anticipate a reward.
The monkeys, which had been taught a computer game that rewarded them with drops of water and juice, lost their slacker ways and worked faster while making fewer errors.
The government researchers used a new technique to temporarily block a gene, known as D2, that normally produces receptors for the brain chemical dopamine - a component in the perception of pleasure.
Terrence Sejnowski, a neurobiologist at the Salk Institute for Biological Studies in San Diego, called the experiment a "tour de force" for opening a new way of modulating brain chemistry.
"The ability to block a specific type of receptor in a specific part of the brain could allow a new generation of therapeutics with fewer side effects," he said.
The results, reported this week in the Proceedings of the National Academy of Sciences, could shed light on mental illnesses that involve motivation, such as obsessive compulsive disorder and mania.
The monkeys' work ethic resembled that of many humans.
"If the reward is not immediate, you procrastinate," said Barry Richmond, a neurologist who led the study at the National Institutes of Mental Health.
During the task, a monkey, perched in a cage in front of a computer monitor, released a lever each time a red dot on the screen turned green. Only quick responses counted.
The number of successes needed for a reward varied - one, two or three. A gray bar on the monitor told the seven monkeys of their progress, brightening as a drink became imminent.
Before their genetic treatment, the monkeys in the test dawdled when the gray bar was dim. Only when it glowed did they become conscientious.
That changed after the scientists performed brain surgery to inject a snippet of DNA known as an "antisense expression vector." The vector suppressed the expression of the D2 gene, hampering the ability of the rhinal cortex to detect dopamine.
The monkeys no longer understood the meaning of the gray bars. As a result, their interest never waned. They worked their levers like obsessed gamblers, never knowing when the jackpot would be delivered. They stopped only after their thirst was quenched.
But don't expect any gene-suppressing injections for chatty office workers or inattentive students.
"Perhaps they would look like manic people all the time," Richmond said.
The Los Angeles Times is a Tribune Publishing newspaper.