Stimulating the brain to treat Parkinson’s disease

10 Feb 2017

Prof Madeleine Lowery. Image: University College Dublin

Prof Madeleine Lowery is modelling the brain, nerves and muscles in a bid to improve technology to treat tremors in Parkinson’s disease. She spoke to Claire O’Connell.

Watching videos of people who have had Deep Brain Stimulation (DBS) treatment to calm the tremors of the progressive neurological condition Parkinson’s disease, it’s obvious what a transformative effect it can have.

The treatment surgically implants an electrode into the brain that delivers electrical pulses to brain cells and motor neurons that control muscles. When it works, it can instantly stop tremors, like the flick of a switch.

DBS has become a relatively mainstream therapy for Parkinson’s disease in recent years, but it’s not a panacea for all. It involves surgery, not only to implant the electrode into the brain but also to place a battery in the chest cavity, and connect the two.

Over time, as the disease progresses, DBS may not manage the symptoms as effectively, and the battery typically needs to be replaced every few years.

There’s scope for improvement, and that is where Prof Madeleine Lowery is on the case. “Essentially, DBS can work really well but it is only prescribed for a small portion of people with Parkinson’s Disease, and we are not completely sure how it works,” she explained.

Towards smarter stimulation

One of the big issues is to know exactly how to fine-tune the stimulator for the individual person, according to Lowery, a professor at University College Dublin (UCD)’s School of Electrical and Electronic Engineering.

“You can set the stimulator to deliver voltage or current pulses at different frequencies and amplitudes. In fact, there are about 2m combinations of parameters you could come up with for DBS,” she said.  

One of the aims of her research, which is funded through the European Research Council, is to come up with a ‘smarter’ DBS system that can figure out the optimal settings for the individual by picking up signals from the muscles and adjusting accordingly.  

That ‘closed-loop’ DBS system is a long way off though. First, Lowery and her research group in UCD need to finish building computer models of the electrode, brain tissue, nerves and muscles involved, and to gather more information from the muscles of healthy volunteers and people with Parkinson’s disease.

Model behaviour

“Our lab is generally interested in how the nervous system works and, in particular, how it controls movement, and we want to use engineering to help to control that movement more smartly in DBS,” she said.  

“We are building computer models of the electrode in the brain and detailed models of the electric field around that, looking at how voltage spreads out through the brain tissue. Then we are modelling the neurons or brain cells that get stimulated, and the motor neurons that carry the signals to the muscle. And finally we model the muscle itself, including muscles controlling the hand.”

The researchers take ‘living’ measurements too, placing electrodes on the muscles of volunteers to see how the nerves and muscles are activated, what forces they generate, and how this changes with fatigue and in Parkinson’s disease.

All of these results will culminate in a model of the entire brain-to-muscle pathway, and will ultimately inform the design of a closed-loop DBS system that can figure out what stimulation is needed in real time.

“We want to use electrophysiological signals from muscles to tune the electrode in the brain,” explained Lowery. “That would mean the system could automatically adjust the parameters to just what is needed at that time to suppress the patient’s symptoms.

“It would avoid delivering too much electrical stimulus, so you are less likely to have side effects and you could also reduce the battery consumption, so the battery would not need to be replaced as often.”

The project is ongoing, but Lowery hopes that the information they gather along the way will shed light not only on how DBS works, but also on some of the muscle and nerve changes that take place in Parkinson’s disease.

Prosthetic arms

It’s not the first time Lowery has researched how biological signals can be harnessed for technology to control movement.

As a postdoctoral researcher at the Rehabilitation Institute of Chicago, she worked with Dr Todd Kuiken on linking nerves to chest muscles to control prosthetic arms.

“The arm may be gone, but parts of the nerves that previously relayed signals from the brain to the arm are still there,” she explained. “So the approach was to reassign those nerves to the pectoral muscle – then the person could use electrical signals from those muscles to control the prosthetic arm just by thinking about the movement they wanted to carry out.”

Multiple paths 

Growing up, Lowery says she was drawn to study both engineering and medicine. Engineering won out, but she now finds herself applying her expertise in a biomedical field.

“I think that is something that students can learn from,” she said. “Choose to study something you like doing and you may circle around to something else you like too – there are often multiple paths that open up. Who knows, had I chosen medicine I might still have been drawn into the research I am doing today.

“So don’t feel like anything is a roadblock, and pick what you enjoy doing.”

Dr Claire O’Connell is a scientist-turned-writer with a PhD in cell biology and a master’s in science communication