Their findings may partly explain cocaine's addictive pull. It might also have meaning for other brain conditions related to dopamine activity such as Parkinson's disease, the researchers write.
The report comes from researchers including Carl Anderson, PhD, of Harvard Medical School and McLean Hospital in Belmont, Mass.
The report appears in Neuropsychopharmacology.
Fresh Look at Old Data
Anderson's team dusted off a small study from 1998 comparing 10 people who used crack cocaine regularly for six or more months and eight other people with no history of drug addictions.
Participants watched two videotapes: one of butterflies, and one of people using crack cocaine. Meanwhile, they got brain scans using functional magnetic resonance imaging (fMRI).
Special attention was paid to the brain's cerebellum, which handles balance and complex actions like walking and talking. The cerebellum is found at the back of the brain, tucked under the much larger cerebrum.
When the study was done in 1998, the researchers looked at the entire cerebellum and didn't see any major differences between the two groups.
Anderson's team re-examined the findings with a closer look. They focused on a part of the cerebellum called the cerebellum vermis.
The cerebellum vermis was especially active when addicts viewed the crack cocaine videotape, the researchers report.
Brain Chemical Clue
Next, the scientists turned their attention to dopamine, a brain chemical which coordinates movement and is stimulated with the use of cocaine.
Their big question: Does the cerebellum vermis have anything to do with dopamine?
Dopamine is important in several brain conditions. For instance, dopamine production falters in people with Parkinson's disease.
The cerebellum had been thought to be largely out of the picture with regards to dopamine, according to the researchers. They note "relatively low concentrations of dopamine and dopamine receptors" in the cerebellum as a whole.
The cerebellum vermis may be involved in the brain's dopamine system, the researchers found.
That's based on their review of past research, which included PET (positron emission tomography) brain scans of 11 healthy people.
"Scientists previously contended that the vermis had little involvement in addiction or other disorders involving dopamine," says Anderson, in a news release. "This changes the perspective on how brain regions may interact during addiction. It introduces an entirely new player."
Anderson's colleagues included Luis Maas, MD, PhD, who had worked on the original videotaped study.