Nav: Home

Evolving deep brain stimulation patterns

January 04, 2017

DURHAM, N.C. -- Duke University biomedical engineers have used computers to "evolve" more effective patterns of electric shocks delivered deep within the brain to treat Parkinson's disease symptoms.

The new energy-saving patterns could reduce the number of battery replacement surgeries needed during a patient's lifetime and lead to patterns tailored to treat specific symptoms.

First introduced in 1987, deep brain stimulation sends electrical pulses deep into the brains of people suffering from neurological motor control diseases through wires implanted into an area of the brain called the basal ganglia. Stimulation greatly improves motor function in many patients, though the reasons why remain unclear.

While trying to understand the basic mechanisms involved, Duke engineers discovered that timing patterns of deep brain stimulation became less effective as they became more random. This implied that there might be non-random patterns that work better than a constant barrage of pulses. Over the past few years, the team has serendipitously discovered several such patterns.

Now, the Duke researchers have built an evolutionary computer algorithm to more purposefully design effective patterns. In a new study with human patients, the program developed a pattern that cuts stimulator energy usage by up to 75 percent while losing none of the treatment's benefits. With a greater understanding of the neural activity that gives rise to specific symptoms, the algorithm could design patterns tailored to each person's needs.

The results appear online on Jan. 4, 2017, in the journal Science Translational Medicine.

"Cutting energy use is important because when these devices' primary cell batteries run out, they have to be replaced through a surgical procedure," said Warren Grill, the Edmund T. Pratt Jr. School Professor of Biomedical Engineering. "Besides being expensive, studies have shown that that there is a 2 to 3 percent chance of infection, which goes up each time the procedure is done. And because these batteries only last three to five years, someone receiving an implant at age 50 could undergo many procedures in a lifetime."

Grill and his colleagues developed timing patterns by splitting each second of electrical pulses into five segments, which they further divided into 200 individual slices. Each segment formed one repetition of a pattern, with each millisecond-long slice randomly receiving a pulse or a blank. With that number of slices and no further restrictions, however, the researchers faced one hundred quindecillion possible patterns. (That's a 1 with 50 zeroes after it -- far too many to test experimentally in a laboratory.)

To pick the most promising patterns out of this impossibly large haystack, the team turned to computational evolution.

"The method works very similarly to biological evolution, but it occurs inside of a computer," said Grill. "In our world, instead of a giraffe's neck getting longer to reach higher leaves, the positions of electric pulses change so that the pattern gets better over time."

The evolutionary algorithm begins by randomly creating 10 patterns of deep brain stimulation and testing them in a computational model of Parkinson's disease. The better a pattern performs, the more likely it is to "parent" a new pattern. In each generation, the computer introduces random mutations into the offspring as well as new "immigrant" patterns to keep the "gene pool" fresh. After thousands of iterations, a new, highly efficient pattern is born.

In this case, the algorithm evaluated the patterns on two measures -- efficiency and effectiveness. By weighting the two appropriately, the computer evolved patterns that used the least amount of energy while maintaining performance just as good as a standard, constant stream of pulses.

The pattern that emerged used an average of only 45 pulses per second -- a large reduction from the standard 130 to 185 used currently. That's an energy savings of 60 to 75 percent, which could double or triple the lifetime of the implanted battery.

After receiving encouraging results from testing the pattern in rats with Parkinson's-like symptoms, Grill decided to test it in humans.

"But modern deep brain stimulation devices can't deliver the patterns we're developing," said Grill. "So we had to come up with an innovative approach."

In collaboration with neurosurgeons at Duke Health and Emory Healthcare in Atlanta, Grill and his team recruited Parkinson's patients with deep brain stimulation implants to test the pattern when they came in for surgical battery replacements. Patients received only local anesthesia during the surgical procedure, retaining control over many motor functions so researchers could assess their symptoms. In between the removal and installation of the new and old batteries, the researchers temporarily connected their test devices to each patient's implanted brain lead to test the new pattern.

The computationally evolved pattern performed just as well as the individually optimized treatments developed by each patient's neurologist over the course of many years, while requiring substantially less energy.

Although it's not yet clear how this abnormal neural activity produces Parkinsonian symptoms--nor exactly how deep brain stimulation is interrupting the oscillations--the study still may provide enough data to bring new relief to patients.
-end-
This research was supported by the National Institutes of Health, including a Javits Neuroscience Investigator Award to Grill to provide long-term support to investigators with a history of exceptional talent, imagination and preeminent scientific achievement (R01-NS040894, R37-NS040894, R01-NS079312).

"Optimized temporal pattern of brain stimulation designed by computational evolution." David T. Brocker, Brandon D. Swan, Rosa Q. So, Dennis A. Turner, Robert E. Gross, Warren M. Grill. Science Translational Medicine, 2016. DOI: 10.1126/scitranslmed.aah3532.

Duke University

Related Brain Articles:

Study describes changes to structural brain networks after radiotherapy for brain tumors
Researchers compared the thickness of brain cortex in patients with brain tumors before and after radiation therapy was applied and found significant dose-dependent changes in the structural properties of cortical neural networks, at both the local and global level.
Blue Brain team discovers a multi-dimensional universe in brain networks
Using a sophisticated type of mathematics in a way that it has never been used before in neuroscience, a team from the Blue Brain Project has uncovered a universe of multi-dimensional geometrical structures and spaces within the networks of the brain.
New brain mapping tool produces higher resolution data during brain surgery
Researchers have developed a new device to map the brain during surgery and distinguish between healthy and diseased tissues.
Newborn baby brain scans will help scientists track brain development
Scientists have today published ground-breaking scans of newborn babies' brains which researchers from all over the world can download and use to study how the human brain develops.
New test may quickly identify mild traumatic brain injury with underlying brain damage
A new test using peripheral vision reaction time could lead to earlier diagnosis and more effective treatment of mild traumatic brain injury, often referred to as a concussion.
This is your brain on God: Spiritual experiences activate brain reward circuits
Religious and spiritual experiences activate the brain reward circuits in much the same way as love, sex, gambling, drugs and music, report researchers at the University of Utah School of Medicine.
Brain scientists at TU Dresden examine brain networks during short-term task learning
'Practice makes perfect' is a common saying. We all have experienced that the initially effortful implementation of novel tasks is becoming rapidly easier and more fluent after only a few repetitions.
Balancing time & space in the brain: New model holds promise for predicting brain dynamics
A team of scientists has extended the balanced network model to provide deep and testable predictions linking brain circuits to brain activity.
New view of brain development: Striking differences between adult and newborn mouse brain
Spikes in neuronal activity in young mice do not spur corresponding boosts in blood flow -- a discovery that stands in stark contrast to the adult mouse brain.
Map of teenage brain provides evidence of link between antisocial behavior and brain development
The brains of teenagers with serious antisocial behavior problems differ significantly in structure to those of their peers, providing the clearest evidence to date that their behavior stems from changes in brain development in early life, according to new research led by the University of Cambridge and the University of Southampton, in collaboration with the University of Rome Tor Vergata in Italy.

Related Brain Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...