Engineers out of UC Berkeley have developed a new type of neurostimulator which has the ability to stimulate and observe electric current in the brain concurrently. This has the potential to offer fine-tuned treatments to patients living with epilepsy.
The device, named the WAND, has been described as a “pacemaker for the brain,” it monitors the brain’s electrical activity and delivers electrical stimulation if it identifies something wrong.
These neurostimulator devices are highly effective in the prevention of tremors or seizures of patients suffering from neurological conditions. However, electrical signatures that precede a seizure are extremely subtle and difficult to track. Therefore the strength and frequency of electrical stimulation which is required to prevent them is highly sensitive. Medical practitioners can spend long periods making small adjustments before the devices provide favourable treatment.
WAND, which stands for wireless artifact-free neuromodulation device, is both wireless and autonomous. This means that once it learns to recognize the signs of a tremor or seizure, it can adjust the stimulation specifications independently to prevent the unwanted movements. It also operates on a closed-loop — this means it can stimulate and record simultaneously and that 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, an 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 is capable of recording electrical activity over 128 channels, or from 128 points in the brain. Previous closed-loop systems have only been able to record up to eight channels. To demonstrate the device, the team used WAND to recognize and delay specific arm movements in rhesus macaques.
Simultaneously stimulating and recording electrical signals in the brain is similar to observing 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.
Current deep brain stimulators will either stop recording while electrical stimulation is being delivered or they will record at a different part of the brain.
“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 Samantha Santacruz, assistant professor at the University of Texas in Austin.
Cortera Neurotechnologies Inc.’s research team, led by Muller, designed the WAND custom integrated circuits. This can record the entire signal from both the subtle brain waves and the more intense electrical pulses. The chip’s design allows WAND to subtract the signal from the electrical pulses. This results in a clean signal from the brain waves.
Previous devices of this nature have only been adapted to record signals from the smaller brainwaves. They became overwhelmed by larger stimulation pulses which made WAND’s new 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.
The research team collaborated with Berkeley EECS computer science professor Jan Rabaey to build a platform device with wireless and closed-loop computational capabilities. This device could be programmed for use in a wide range of research and clinical applications.
In experiments lead by Santacruz while a postdoc at UC Berkeley, and by 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,” she said.