Dopamine is a neurotransmitter perhaps best known for being associated with the brain’s reward system. However, dopamine has several functions. It regulates motivation, motor control, and spatial working memory. A recent study showed that dopamine is also involved in processing rules in the prefrontal cortex (PFC), the part of the brain in charge of abstract thought and executive functioning.
Image source: Science Photo Library – PASIEKA
In the study, two rhesus monkeys were trained to complete a task in which they were shown an initial sample of dots. In one scenario, researchers gave them a cue to apply the “greater than” rule: after a subsequent test sample was shown, the monkeys had to release a lever if the test sample had more dots than the original sample. In another scenario, they were given a cue to apply the “less than” rule: they had to release the lever if the test sample had fewer dots than the original sample.
Knowing that the monkeys used half of certain PFC “rule neurons” for the “greater than” scenario and the other half for the “less than” scenario, the researchers administered dopamine agonists (substances that mimic the effect of dopamine) and dopamine antagonists (substances that oppose the effect of dopamine) in the brain to activate or inhibit these neurons. They found that activation of the “rule neurons” by dopamine agonists enhanced their ability to distinguish between “greater than” and “less than” and thus their performance of the numerical rule switching task.
These findings indicate that dopamine in the prefrontal cortex plays a role in facilitating goal-directed behavior and applications of mathematical rules. This knowledge can be used to better understand the effects of medications for psychological disorders that are known to affect dopamine levels in the prefrontal cortex.
Feature Image Source: Daydreamer by Darren Puttock
