Take your time. Hold the horses. Overnight. When people must decide between the equally likely choices, they need time to deliberate. In the case of people with deep brain stimulation (DBS) for Parkinson's disease, a process that is not always in football, which is an impulsive behavior. Some people who receive deep brain stimulation for Parkinson's disease, behave impulsively, so fast, that decisions are often wrong.
New research on why that happens has led scientists to a detailed explanation of how the brain takes time to reflect on the tough decisions.
Michael Frank, professor of cognitive, linguistic and psychological sciences at Brown University, studied the impulsive behavior of patients with Parkinson's when he was at the University of Arizona several years ago. His goal was to model the decision-making mechanism of the brain. He began working with patients with Parkinson's disease because of the DBS, a treatment that suppresses the symptoms tremor that delivers pulses of electric current in the subthalamic nucleus (STN), a part of the brain that assumption of Frank had an important role in decisions. STN may be slamming the brakes on the impulses that give the medial prefrontal cortex (mPFC) time to think?
When the medial prefrontal cortex need time to consider it recruits help avoid impulsive urges elsewhere in the brain. "We had no direct evidence for it," said Frank, who is affiliated with Brown Institute for Brain Science. "To test this theory on how brain areas interact to prevent you from making impulsive decisions and how this can be changed by DBS, you have to do experiments where you record brain activity in both parts of the network that we believe are involved. So you also need to manipulate the system to see how the relationship between the activity recorded in an area and make changes according to stimulate the other domain. "
Frank and his team at Brown, and Arizona did just that. These are the results of the research were published online in the journal Nature Neuroscience.
The researchers' measurements of both experiments and computer model analysis support the theory that when the mPFC is facing a difficult decision, which recruits more impulsive momentum STN to exorcise the striatum, a third of the brain. This allows time for a decision.
For their first experiments, the researchers designed a computerized decision-making experience. They asked 65 healthy volunteers and 14 patients with Parkinson's disease to choose between pairs of generic art images online while their brain activity was recorded mPFC. Each image, each associated with a level of reward. Over time, subjects learn which completed a major award.
Sometimes, however, issues would be confronted with images of almost the same reward - a choice quite difficult. It is when the scalp electrodes detected a high activity in the mPFC in certain low frequency band. The lead author and postdoctoral fellow James Cavanagh found that when mPFC activity was higher, would be healthy participants and participants with Parkinson's when pacemakers were out takes proportionally more time to decide. But when the DBS was turned on to change the RTC mode, the relationship between activity and decision mPFC reversed, leading to the decision, which was faster and less accurate.
Patients with Parkinson's pacemaker showed the same high level of activity in the mPFC. The crust had the deliberate purpose, Cavanagh said, but the link with the brakes have been reduced.
"Patients with Parkinson on the DBS had similar signals," he said. "It does not relate to behavior. We eliminated the network."
In another experiment, the researchers presented eight patients at the same time, making the game while on an operating table in Arizona will receive their DBS implantation. The researchers used an electrode to record the events directly to the STN, and found a pattern of brain activity patterns, are closely observed in the mPFC.
"STN is more action and more times, [the decision] conflict," he said. "It 'a response to situations that the signals on the scalp to respond, and very similar to the frequency ranges and intervals of time."
A mathematical model to analyze the accuracy and extent of the response time has confirmed that the increase in neural activity, and people have had time to decide because the test was processed hard.
"It was not what was expected and do nothing," said graduate student Thomas Wieck, the second author of the article. "It's been slower since you took the time to make a more informed decision. They were treated in greater depth."
The results led researchers to believe that perhaps the various brain areas communicate with these low frequency signals. Perhaps impulsive side effects of DBS could be overcome if these bands could remain without being bothered by the pacer signal. Alternatively Wieck said, a more sophisticated DBS, could feel that the resolution of conflict in the mPFC and either temporarily suspend its activities pending a decision, or stimulate the STN of a more dynamic way to better imitate the STN function intact.
These ideas are not trivial to pass engineering DBS, but by understanding the mechanics behind the side effects - and sound decision making unfettered - Scientists say they now have a goal to consider.
Besides Frank, Cavanagh and Wieck, another author Christina Brown Figueroa. The authors include Arizona, Michael Cohen, Johan Samanta, and Scott Sherman.
People With Deep Brain Stimulation
