Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Impulsivity, rewards and Ritalin: Monkey study shows tighter link

14.11.2013
Even as the rate of diagnosis has reached 11 percent among American children aged 4 to 17, neuroscientists are still trying to understand attention deficit hyperactivity disorder (ADHD). One classic symptom is impulsivity — the tendency to act before thinking.

Scientifically, impulsivity can appear as a choice for a small but immediate reward over a larger one that requires some delay. Choosing between present and future rewards is a fundamental need in schooling, says Luis Populin, associate professor of neuroscience at University of Wisconsin-Madison.

"If you say to an impulsive child, 'Do your homework so you will get a good grade at the end of the quarter,' that has less appeal than 'Let's play baseball this afternoon instead of studying chemistry.'"

To study impulsive behavior, Populin and graduate student Abigail Zdrale Rajala selected two rhesus macaque monkeys with opposite behaviors. One was extremely calm, while the other was nervous, fidgety and impulsive. The monkeys were trained to stare at a dot on a screen and, when it went dark, to choose between two pictures placed to the side. Their choice of picture determined whether they got a small but immediate sip of water, or a larger sip, after a delay ranging up to 16 seconds.

As expected, the calm monkey, but not the impulsive one, quickly figured out that waiting would bring the sweeter result.

This willingness to take a smaller reward right away rather than a larger, delayed reward, called "temporal discounting," is a common feature of "combined type" ADHD, which specifically lists impulsivity among its diagnostic criteria, Populin says.

When the monkeys were given a dose of methylphenidate, the active ingredient of the common ADHD drug Ritalin, they chose the delayed reward more frequently. The impulsive monkey actually showed the same preference for delayed rewards as the unmedicated, calm monkey. However, identifiable differences in their performance mean that methylphenidate improved the condition, but did not eliminate it.

"There is no perfect animal model of ADHD," says Rajala, "but many studies are performed on rodents; this one was done in a non-human primate, which is much closer to humans." The Society for Neuroscience adjudged the paper valuable enough to support Rajala's travel to the conference in San Diego.

Methylphenidate changes the elimination of dopamine, a "reward" neurotransmitter that is elevated by drugs like cocaine and amphetamine. The result is that more dopamine remains in the brain, which is the most likely explanation for the altered reward processing in the medicated monkeys.

Some scientists have thought that temporal discounting in ADHD may result from cognitive processing, which relies on the highly evolved frontal cortex in the brain. The new results support an alternative, but less common, hypothesis: that temporal discounting is linked to the reward-processing mechanism, which is governed by more primitive parts of the brain.

By teasing apart one characteristic of ADHD, the study could help refine drug or behavioral treatments of a disability that has grown 16 percent more common just since 2007, Populin says.

David Tenenbaum
608-265-8549
djtenenb@wisc.edu
CONTACT:
Luis Populin
608-265-6451
lpopulin@wisc.edu
Abigail Zdrale Rajala
608-265-6711
azdrale@gmail.com

Luis Populin | EurekAlert!
Further information:
http://www.wisc.edu

Further reports about: ADHD Monkey Monkey study Populin frontal cortex impulsivity rhesus macaque monkeys

More articles from Studies and Analyses:

nachricht Researchers simplify tiny structures' construction drip by drip
12.11.2018 | Princeton University, Engineering School

nachricht Mandibular movement monitoring may help improve oral sleep apnea devices
06.11.2018 | Elsevier

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>