How do you make a tough choice? For most people, the answer is to pause and deliberate, as the brain puts the brakes on its initial impulses. Deep brain stimulation (DBS) used to treat Parkinson’s disease, however, can interfere with this braking action, according to new research that is starting to reveal the anatomy of choice.
Parkinson’s disease, which affects at least half a million Americans, is a progressive neurological disorder that is characterized by tremors and difficulty initiating and controlling movement, and can lead to dementia. Deep brain stimulation — which uses a device implanted in the brain like a pacemaker — can reduce symptoms when drug treatments fail.
DBS affects a part of the brain called the subthalamic nucleus (STN), which in turn affects multiple systems, according to Michael Frank, professor of cognitive, linguistic and psychological sciences at Brown University. During decision-making, it inhibits impulsive urges originating in a brain region known as the striatum. This allows a “pause,” during which slower deliberation can take place in an area called the medial prefrontal cortex (mPFC).
The STN also affects movement in Parkinson’s patients. “If the STN is really active, people have a hard time initiating movement,” Frank says, which helps explain why people with Parkinson’s may suffer from physical immobility or undirected shaking or become trapped in this “pause.”
Consequently, DBS is used to regulate STN activity to ease movement. If it overshoots, however, it may allow impulses from the striatum to slip past the mPFC. That can sometimes lead to impulsive, unwise decision-making — and an increased risk of addictive disorders like gambling problems. Read the rest of the article here.