“Anytime you have a change in behavior you have a change in the brain,” said UCLA psychiatrist Dr. Lewis Baxter. “Behavior therapy and drugs appear to rearrange brain circuitry in the same way.”
Baxter and his colleagues studied the brains of obsessive-compulsive patients with PET (positron emission tomography) scans, a technique that measures the activity of cells in different areas of the brain. They found that an area called the caudate nucleus was overactive in these patients.
The caudate nucleus acts as a gate-keeper that prevents unwanted thoughts from establishing self-reinforcing circuits in the brain. Like a record stuck in the same groove, unwanted thoughts keep repeating themselves and drive compulsive behavior.
Fluoxetine (Prozac) is highly effective in curbing unwanted thoughts through a mechanism that is little understood, but which involves raising the level of an important brain chemical messenger called serotonin.
Behavior therapy, which is also effective in breaking unwanted habits, involves gradual exposure to a fear-triggering agent, such as dirt, and teaching a patient not to respond to compulsive urges.
Although the two treatments appear to be highly dissimilar, PET scans showed that they produced identical changes in calming down caudate nucleus activity in both groups.
Both therapies appear to correct the abnormal circuits causing unwanted thoughts by changing connections between brain cells in the caudate nucleus, Baxter said.
The caudate nucleus has been implicated with voluntary movement, learning, memory, sleep, and social behavior. The caudate nucleus is highly innervated by dopamine neurons.
- A 2013 study has suggested a link between Alzheimer’s patients and the caudate nucleus
- Parkinson’s disease depletes dopaminergic neurons in the nigrostriatal tract, a dopamine pathway that is connected to the head of the caudate. As such, many studies have correlated the loss of dopaminergic neurons that send axons to the caudate nucleus and the degree of dementia in Parkinson’s patients.
- A 2002 study draws a relationship between caudate asymmetry and symptoms related to ADHD.
- The volume of white matter in the caudate nucleus has been linked with patients diagnosed with Schizophrenia.
- It has been theorized that the caudate nucleus may be dysfunctional in persons with obsessive compulsive disorder (OCD).