A new neurostimulator de­veloped by engineers at UC Berkeley can listen to and stimulate electric current in the brain at the same time, po­tentially delivering fine-tuned treatments to patients with dis­eases like epilepsy and Parkin­son’s.
The device, named the WAND, works like a “pace­maker for the brain,” monitor­ing the brain’s electrical activ­ity and delivering electrical stimulation if it detects some­thing amiss.
These devices can be ex­tremely effective at preventing debilitating tremors or seizures in patients with a variety of neurological conditions. But the electrical signatures that precede a seizure or tremor can be extremely subtle, and the frequency and strength of elec­trical stimulation required to prevent them is equally touchy. It can take years of small ad­justments by doctors before the devices provide optimal treat­ment.
WAND, which stands for wireless artifact-free neuro­modulation device, is both wireless and autonomous, meaning that once it learns to recognize the signs of tremor or seizure, it can adjust the stimulation parameters on its own to prevent the unwanted movements. And because it is closed-loop — meaning it can stimulate and record simulta­neously — it can adjust these parameters in real-time.
“The process of finding the right therapy for a patient is extremely costly and can take years. Significant reduction in both cost and duration can potentially lead to greatly im­proved outcomes and accessi­bility,” said Rikky Muller as­sistant professor of electrical engineering and computer sci­ences at Berkeley. “We want to enable the device to figure out what is the best way to stimu­late for a given patient to give the best outcomes. And you can only do that by listening and re­cording the neural signatures.”
WAND can record electri­cal activity over 128 channels, or from 128 points in the brain, compared to eight channels in other closed-loop systems. To demonstrate the device, the team used WAND to recognize and delay specific arm move­ments in rhesus macaques. The device is described in a study that appeared today (Dec. 31) in Nature Biomedical Engi­neering.
Ripples in a pond
Simultaneously stimulating and recording electrical signals in the brain is much like trying to see small ripples in a pond while also splashing your feet — the electrical signals from the brain are overwhelmed by the large pulses of electricity delivered by the stimulation.
Currently, deep brain stimu­lators either stop recording while delivering the electrical stimulation, or record at a dif­ferent part of the brain from where the stimulation is ap­plied — essentially measuring the small ripples at a differ­ent point in the pond from the splashing.
“In order to deliver closed-loop stimulation-based thera­pies, which is a big goal for people treating Parkinson’s and epilepsy and a variety of neurological disorders, it is very important to both perform neural recordings and stimu­lation simultaneously, which currently no single commer­cial device does,” said former UC Berkeley postdoctoral as­sociate Samantha Santacruz, who is now an assistant profes­sor at the University of Texas in Austin.
Researchers at Cortera Neu­rotechnologies, Inc., led by Rikky Muller, designed the WAND custom integrated cir­cuits that can record the full signal from both the subtle brain waves and the strong electrical pulses. This chip de­sign allows WAND to subtract the signal from the electrical pulses, resulting in a clean sig­nal from the brain waves.
Existing devices are tuned to record signals only from the smaller brain waves and are overwhelmed by the large stimulation pulses, making this type of signal reconstruction impossible.
“Because we can actually stimulate and record in the same brain region, we know exactly what is happening when we are providing a ther­apy,” Muller said.
In collaboration with the lab of electrical engineering and computer science profes­sor Jan Rabaey, the team built a platform device with wire­less and closed-loop compu­tational capabilities that can be programmed for use in a variety of research and clinical applications.
In experiments lead by Santacruz while a postdoc at UC Berkeley, and by and elec­trical engineering and com­puter science professor Jose Carmena, subjects were taught to use a joystick to move a cur­sor to a specific location. After a training period, the WAND device was capable of detect­ing the neural signatures that arose as the subjects prepared to perform the motion, and then deliver electrical stimula­tion that delayed the motion.
“While delaying reaction time is something that has been demonstrated before, this is, to our knowledge, the first time that it has been demonstrated in a closed-loop system based on a neurological recording only,” Muller said.
“In the future we aim to incorporate learning into our closed-loop platform to build intelligent devices that can fig­ure out how to best treat you, and remove the doctor from having to constantly intervene in this process,” said Muller said.
Andy Zhou and Benjamin C. Johnson of UC Berke­ley join Santacruz as co-lead authors on the paper. Other contributing authors include George Alexandrov, Ali Moin and Fred L. Burghardt of UC Berkeley. This work was sup­ported in part by the Defense Advanced Research Projects Agency (W911NF-14- 2- 0043) and the National Sci­ence Foundation Graduate Research Fellowship Program (Grant No. 1106400). Authors Benjamin C. Johnson, Jan M. Rabaey, Jose M. Carmena and Rikky Muller have financial interest in Cortera Neurotech­nologies, Inc., which has filed a patent application on the inte­grated circuit used in this work.