ASU research on impulsivity may help in understanding how young adults and children are behaviorally affected by ADHD.
Federico Sanabria, the principal investigator for the research project, is an assistant psychology professor at the Tempe campus.
“We’re basically doing research on impulsivity and developing a procedure to test a particular kind of impulsivity that characterizes ADHD,” Sanabria said.
Impulsivity that relates to ADHD is defined as “an ability to withhold a response that would otherwise be very likely to happen,” he said.
Sanabria said he uses animal models, such as rats, for the research in order to “develop a procedure to evaluate [impulsivity].”
“The reason why we’re particularly interested in rats is because there is a particular strain of rats that is thought to be an animal model of ADHD in general,” Sanabria said.
Overall, ADHD has multiple features, including attention, impulsivity and hyperactivity components, he said. The research focuses solely on impulsivity, though.
Part of the research observes how the psycho-stimulant drug methylphenidate (or Ritalin) affects rats, Sanabria said, which will help deliver results consistent with effects of the drug seen in humans.
In the experiments with the drug, the special strain of rats (known as the Spontaneously Hypertensive Rat) are not yet used, Sanabria said.
However, the specific strain is put through experiments that make the rats create an association between pressing a lever and being rewarded with food, he said.
The rats were expected to press the lever and wait 6 seconds for food, Sanabria said.
“The special strain of rats was holding down the lever for much less [time than the normal rats], suggesting that these are in fact impulsive animals,” he said.
This first test doesn’t allow the rats to do any other activities while waiting for the food reward, Sanabria added.
This led Sanabria to do another type of test to introduce a new procedure to deliver results analogous to the ones found in humans, including drug effectiveness.
“What we wanted to do is develop a task where we can actually allow the animal to engage in activities while waiting,” Sanabria said.
When the experiment allows animals to participate in alternative activities, there is an obvious increase in participation, he said.
“The animal engages more in lever-pressing that has nothing to do with the task [while waiting],” Sanabria said.
The activities include continually pressing the lever without punishment as well as sticking its head inside the hole where food is delivered to obtain its reward, he said.
“What it’s showing is that the way that the drug might be helping kids with impulsivity is making it easier for them to engage in alternative activities that may not be so enjoyable for them, but that will allow them to pass the time while they are waiting,” Sanabria said.
Sanabria said research has found that there is substantial evidence on how methylphenidate works at the neurological level, but “we don’t know what it is exactly at the behavioral level that is making it easier for the kids to wait.”
Future research might help college students self-diagnose themselves and get help for ADHD, potentially even from the convenience of a laptop.
“[The student can] compare himself against the mean of the national population or the mean of other college students and see if he is responding too fast or if he is having problems waiting relative to other students,” Sanabria said.
Psychology graduate student Jade Hill works with Sanabria in the study.
“We’re trying to publish the paper [on the current project] in a journal called Behavioral Pharmacology that looks at a lot of processes like this,” Hill said.
There’s an issue of the magazine devoted to impulsivity that is coming out at the end of March — although the research team has not submitted a paper yet, she said.
“By studying the mechanisms and studying the specific behaviors that are changed with methylphenidate, we can get an idea of what’s changing and of how to best change children and people’s behavior [who have ADHD or other disorders],” Hill said.
Reach the reporter at reweaver@asu.edu.
