The Impulsive Brain

For some time now, scientists have thought that impulsive behavior is linked, in some way, to the neurotransmitter dopamine, which causes a "reward" feeling in the brain. But how?

According to a new paper from a team of researchers at Vanderbilt University, impulsive people have fewer dopamine receptors in the midbrain, and this deficit affects the level of dopamine in other parts of the brain. When these people are given a stimulant that triggers the release of dopamine, they release much more of the chemical in a part of the brain called the striatum than nonimpulsive people do. The excess, it seems, is due to the fact that the dopamine receptors in the midbrain appear to regulate how much of the chemical is released in the striatum. Since this dopamine is important for organizing behavior to obtain things that feel good, it makes sense that these people would be more likely to do things that give them this rush. As Joshua Buckholtz, a doctoral student who led the study, describes in a write-up of the research:

The brain has a number of different thermostats, which sense the levels of certain brain chemicals and adjust the output of those chemicals accordingly. We show that one particular thermostat-like mechanism—midbrain autoreceptor regulation of striatal dopamine release—is out of whack in people with high levels of trait impulsiveness.