October 2 : Researchers at the University of Arizona have found links to learning behaviours in three separate genes associated with dopamine, a chemical in the brain that is often associated with pleasure, learning and other behaviours.

Michael Frank, an assistant professor of psychology and director of the Laboratory for Neural Computation and Cognition at The University of Arizona, says that his study points to fundamental genetic differences between “positive” and “negative” learners.

“All three genes affect brain dopamine functioning, but in different ways, and in different parts of the brain. The genes predicted people’s ability to learn from both the positive and negative outcomes of their decisions,” he said.

The researcher said that two of the genes—DARPP-32 and DRD2— control dopamine function in a region of the brain called the striatum, and they predict learning about the average, long-term probability of rewards and punishments, not unlike ones personal preference for why, for example, one might choose steak over salmon.

“When making these kinds of choices, you do not explicitly recall each individual positive and negative outcome of all of your previous such choices. Instead, you often go with your ‘gut,’ which may involve a more implicit representation of the probability of rewarding outcomes based on past experience,” he said.

Frank further said that the third gene, COMT, did not predict long-term reward or punishment learning, but instead predicted a person’s tendencies to change choice strategies after a single instance of negative feedback.

He revealed that this gene affects dopamine function in the prefrontal cortex of the brain, the area associated with conscious processing and working memory.

“The reason we looked at these three individual genes in the first place, out of a huge number of possible genes, is that we have a computer model that examines how dopamine mediates these kinds of reinforcement processes in the striatum and prefrontal cortex,” Frank said.

“The model makes specific predictions on how subtle changes in different aspects of dopamine function can affect behaviour, and one way to get at this question is to test individual genes,” he added.

During the study, the researchers collected DNA from 69 healthy individuals who were asked to perform a computerized learning program. The volunteers were asked to pick one of two Japanese characters that appeared on a screen, and were “rewarded” for a “correct” response, and “punished” for an “incorrect” one.

The study showed that dopamine production increased in the wake of unexpected rewards, and that it declined when rewards were expected but not received.

Frank said more research was needed to confirm that genetic effects are accompanied by brain-related changes in behaviour, but insisted that the study offered insights into the genetic basis for learning differences, and into improving cognition and learning in humans, both normal and abnormal.

“Understanding how dopaminergic variations affects learning and decision-making processes may have substantial implications for patient populations, such as (those with) Parkinson’s disease, attention-deficit hyperactivity disorder (ADHD) and schizophrenia,” Frank said.

“The genetics might also help us identify individuals who might gain from different types of learning environments in the classroom,” he added. (ANI)