Low-frequency Brain Stimulation Improves Parkinson’s Patients’ Thinking Ability, Study Shows

Using low-frequency electrical pulses to stimulate a deep brain region can improve the cognitive function of people with Parkinson’s and other neurological diseases, a study suggests.

The U.S. Food and Drug Administration has already approved high-frequency deep brain stimulation as a way to treat Parkinson’s. A team at the University of Iowa’s Neuroscience Institute showed that low-frequency stimulation is also a promising approach.

Their study also showed for the first time that there is a direct link between the thinking region of the brain — the frontal cortex — and the area that controls movement — the subthalamic nucleus, or STN.

The research, “A human prefrontal-subthalamic circuit for cognitive control,” was published in the journal Brain.

“It’s not very often that you identify a new connection in the human brain,” Dr. Nandakumar Narayanan, an assistant professor of neurology at the university’s Carver College of Medicine, said in a news release.

“The existence of this hyperdirect pathway from the prefrontal cortex to the STN has been bandied about for around a decade, but this is the first time we’ve experimentally shown that it exists and functions in people,” added Narayanan, the study’s senior author.

Jeremy Greenlee, a medical school neurosurgeon who co-authored the study, performed more than 30 surgeries to implant deep brain stimulation electrodes in Parkinson’s patients.

During the surgeries, while patients were still awake, the team recorded the activity in their  subthalamic nucleus and other brain regions.

Researchers also asked patients to do a simple cognitive task while they were in surgery. As they did so, the team stimulated their frontal cortex, recording activity in brain areas connected to it. This allowed the team to identify signals that suggested a direct connection between brain regions.

“We were able to evoke a response to show the functional connection,” Greenlee said. “The very fast response suggests a single, direct synaptic connection — that is what hyperdirect means.”

In follow-up visits, patients were asked to perform interval timing tasks again. Researchers alternated between setting their brain electrodes to high frequency or low frequency, or not sending electrical pulses at all.  Surprisingly, patients performed their task faster with low-frequency stimulation than with high-frequency or no stimulation.

“If we stimulate the STN and change cortical activity, we can actually change behavior in a beneficial way, improving the patients’ cognitive performance,” Narayanan said.

“It is exciting to potentially have a way to improve cognition that could be life-changing for patients,” Greenlee said.

This study was funded in part by two U.S. government agencies — the National Institute of Neurological Disorders and Stroke and the National Institute on Deafness and Other Communication Disorders.