A new study finds that rats with impulsive tendencies tend to have poorer working memories. Scientists define working memory in people as the ability to hold details like a name or phone number in mind.
On the other hand, rats that avoided risky situations tend to have poor cognitive flexibility, which in this case means they were unable to learn a new way to get a food pellet after they had been trained to expect it from a different lever.
By studying the rats’ behavior, researchers are examining the ways impulsivity, working memory, and cognitive flexibility may or may not interact.
Published online in the journal Neurobiology of Learning and Memory, the study could provide animal models for people with certain mental disorders such as anorexia or addiction, says Kristy Shimp, a doctoral candidate at the University of Florida.
People with anorexia tend to have poorer cognitive flexibility, whereas people with addiction often engage in risky behavior.
“Instead of treating psychiatric disorders based on a cluster of symptoms and a single diagnosis, the National Institutes of Health is shifting to treating separate symptoms,” Shimp says. “Researching things like risky decision-making, impulsivity, and other features that are part of multiple disorders is becoming more important.”
Now or Later?
To study impulsivity, Shimp’s rats were presented with two levers. Pressing the first lever yielded the rats one pellet right away. If the rats pressed the other lever, however, they got three pellets of food—but only after a delay.
The delay increased as the test went on. Some rats were able to delay gratification, continuing to choose the large reward even when they had to wait for it. But other rats still opted for the smaller amount of food that came more quickly.
The finding that impulsive rats have poor working memories echoes research conducted at Virginia Tech with people addicted to methamphetamine, who had poor working memories and tended to be more impulsive than non-users.
But, this earlier research showed, when given computer-based working memory training, the subjects’ working memory strengthened and their impulsivity decreased. Similarities between the results of the two studies could give researchers a new animal model to study the neurobiology underlying addiction.
“Better working memory leads to less impulsivity. Intuitively, if you have a more salient recall that, ‘Hey, if I do drugs, bad things will happen,’ you’d be less likely to use drugs,” she says.
In humans, it is difficult to study whether their behavior is a result of genetics or a result of other environmental factors, or both. Neuroscientist Barry Setlow, who is a coauthor on the paper, says the team’s goal is to examine both the genetic and environmental causes of risky behavior, impulsivity, and addiction. “In this experiment, the rats all came from a very homogenous background,” he says.
Understanding how these features are connected may help change medical treatment for people with attention deficit hyperactivity disorder, schizophrenia, addiction, and other disorders associated with risk-taking.
“While pharmaceuticals can be very helpful, there may be side effects. Things like exercise and mental diversion in addition to typical kinds of therapies could be helpful,” Shimp says. “We can find natural ways that can help people modify their behavior in a healthy way.”