Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study pinpoints effects of different doses of an ADHD drug; Finds higher doses may harm learning

09.03.2012
New research with monkeys sheds light on how the drug methylphenidate may affect learning and memory in children with attention deficit hyperactivity disorder.

The results parallel a 1977 finding that a low dose of the drug boosted cognitive performance of children with ADHD, but a higher dose that reduced their hyperactivity also impaired their performance on a memory test.

"Many people were intrigued by that result, but their attempts to repeat the study did not yield clear-cut results," says Luis Populin, an associate professor of neuroscience at the University of Wisconsin-Madison School of Medicine and Public Health.

Populin was senior author of the new study exploring the same topic, now available in the early access section of the Journal of Cognitive Neuroscience, published last week. In the study, three monkeys were taught to focus on a central dot on a screen, while a "target" dot flashed nearby. The monkeys were taught that they could earn a sip of water by waiting until the central dot switched off, and then looking at the location of the now-vanished target dot.

The system tests working (short-term) memory, impulsiveness and willingness to stick with the task, as the monkeys could quit "working" at any time, says Populin. The study used different doses of methylphenidate -- the generic name for Ritalin -- that were comparable to the range of clinical prescriptions for ADHD.

According to the Centers for Disease Control, almost 5 percent of American children are taking medications for ADHD.

Strikingly, dosage had a major and unexpected impact. "At a low dose, the performance scores improved because the monkeys could control their impulses and wait long enough to focus their eyes on the target. All three were calmer and could complete a significantly larger number of trials," says Populin, who collaborated with Jeffrey Henriques and graduate student Abigail Rajala on the study.

At the higher dose, "performance on the task is impaired," Populin says, "but the subjects don't seem to care, all three monkeys continued making the same errors over and over." The monkeys stayed on task more than twice as long at the higher dose, even though they had much more trouble performing the task.

Although ADHD drugs are commonly thought to improve memory, "If we take the accuracy of their eye movements as a gauge of working memory, memory was not helped by either dose," says Populin. "It did not get better at the lower dose, and there actually was a small negative effect at the higher dose."

Memory is at the root of many intellectual abilities, but it can be affected by many factors, says Bradley Postle, a professor of psychology at UW-Madison.

Postle, an expert on working memory who was not involved in the study, says methylphenidate affects the brain's executive function, "which can create an internal environment that, depending on the dose, is either more or less amenable to memory formation and/or retention. If you can concentrate, and are able to process information without being interrupted by distracting thoughts or distractions in your environment, you will perform much better on a memory test. Apparently, the lower dose of methylphenidate helped create the conditions for success without actually improving memory itself."

Monkeys are not people, but monkeys in the study still reminded him of school children, Populin says.

"They made premature movements, could not wait to look at the target before they could be rewarded for doing so. It's like a kid where the teacher says, 'When you complete the task, raise your hand.' But he can't wait, even if he knows that by responding prematurely he will not get rewarded," he says.

The study results had another parallel with daily life, Populin says. Drug dosages may be set high enough to reduce the characteristic hyperactivity of ADHD, "but some children say that makes them feel less creative and spontaneous; more like a robot. If learning drops off as it did in our study, that dose may not be best for them. Our monkeys actually did act like robots at the higher doses, keeping at it for up to seven hours even though their performance was so low."

The logical way forward would involve a similar study with people diagnosed with ADHD, Populin says. With millions of children, and an increasing number of adults, taking medicines for the condition, "We have to be very careful about finding the right spot on the dose curve, or we may get changes in behavior that we don't want. People think these drugs help improve memory, but our data say, 'No, your memory is not getting better.' At the higher dose, you get a behavioral improvement at a price, and that price is cognitive ability."

David Tenenbaum, 608-265-8549, djtenenb@wisc.edu

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

More articles from Health and Medicine:

nachricht New High-Performance Center Translational Medical Engineering
26.04.2017 | Fraunhofer ITEM

nachricht A promising target for kidney fibrosis
21.04.2017 | Brigham and Women's Hospital

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Scientist invents way to trigger artificial photosynthesis to clean air

26.04.2017 | Materials Sciences

Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli

26.04.2017 | Agricultural and Forestry Science

SwRI-led team discovers lull in Mars' giant impact history

26.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>