University of Iowa researchers identified a connection between a routine treatment for Parkinson’s disease and a tendency for some patients to develop increased impulsivity located around a specific brain region in a study published March 4.

The research identified the subthalamic nucleus as a structure in the brain that specifically contributes to attention deficiencies, though it was previously known to be an affected area in Parkinson’s disease.

Performed by a team led by associate professor of psychological and brain sciences and neurology Jan Wessel, the study found the area to be more involved than previously known as a result of a popular treatment called deep brain stimulation.

Wessel said deep brain stimuli are effective for patients who have not sufficiently benefitted from dopamine medication, which is the initial option for Parkinson’s treatment. The procedure consists of surgeons triangulating the proper area of the patient’s brain to plant an electrode at the subthalamic nucleus, Wessel said.

That electrode is then turned on, and the stimulus helps to mitigate the tremors resulting from Parkinson’s disease, Wessel said.

Wessel said an important element of the research study was the identification of where cognitive issues resulted from the deep brain stimulus. Approximately 20 percent of patients who undergo deep brain stimulus can develop cognitive issues, according to a 2006 study. Wessel’s team set out to identify the connection.

Cognitive issues eventually arise in time with Parkinson’s, Wessel noted. Research studies in the past have found attention issues, he said, but the UI research identified a greater connection between deep brain stimulus and an increased occurrence of attention deficiencies.

Using brainwave recordings, Wessel’s team identified a decrease in focused attention by seeing how well patients with the electrode can focus on a visual object when an unexpected sound is played.

Wessel said the procedure’s ability to prevent the physical impulses, which he described as “braking,” in the identified brain region can also reduce the same braking of mental impulses.

The reduced braking of cognitive impulses results in attention deficiencies or even leads to unregulated impulsivity, such as the development of pathological gambling in some patients, Wessel said.

Wessel said some of the next steps are to look closer at regions of the brain to identify smaller and smaller sections that differ from each other to find the specific source of cognitive versus physical braking.

It is important for patient’s doctors to be on the lookout for any side effects of the treatment, Wessel said.

“This technique, which is a really miraculous technique, can have side effects. Doctors can be on the lookout,” Wessel said.

Qiang Zhang, a fellow researcher involved with Wessel’s study and who monitors patients after their operations, said deep brain stimulus is like a new medication.

“Your doctor will tell you that you have to double the dose in two days,” Zhang said. “And if there’s a side effect, go back. My role is to determine how strong and how exactly we should stimulate the brain with the new drug.”

Zhang said physical side effects rarely occur rapidly when a patient comes back to the clinic and is experiencing dramatic movement issues. Cognitive side effects take longer to develop. These all can be addressed by changing the level at which the electrode functions.

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Jeremy Greenlee is a neurosurgeon who works for UIHC and is the doctor who works directly with the deep brain stimulus procedure. Greenlee said he worked with Wessel to administer the deep brain stimulus while Wessel’s team performed their experimental analysis.

“He’s a great scientist, and it’s a great opportunity for us as a field to learn more from these kinds of unique test settings that we have the privilege to have in front of us,” Greenlee said.

Greenlee said the side effects are ultimately not harmful enough to ignore the improvements a person may see as a result of deep brain stimulation. He believes Wessel’s research has proven beneficial for future treatment.

“The benefits far outweigh these low risks,” Greenlee said. “These are fun patients to take care of and they come back like different people.”