Wireless ‘pacemaker for the brain’ could be new standard treatment for neurological disorders

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, 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 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 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 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 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.



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