The wireless, artifact-free neuromodulation device (WAND) works like a “pacemaker for the brain,” monitoring its electrical activity and delivering electrical stimulation if it detects something amiss, according to the researchers.
Deep-brain stimulators currently on the market either stop recording while delivering electrical stimulation or record at a different part of the brain from where the stimulation is applied because the electrical signals from the brain are overwhelmed by the large pulses of electricity delivered by the stimulation, the researchers said. They likened the work of these stimulators to measuring small ripples in a pond at a different point from which the splash that creates the ripples takes place.
Also, the electrical signatures that precede a seizure or tremor can be quite subtle and the frequency and strength of electrical stimulation required to prevent them must be precise. It can take years of small adjustments by doctors before the devices provide optimal treatment.
“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 lead researcher Rikky Muller of Cortera Neurotechnologies and an assistant professor of electrical engineering and computer sciences at UC 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’s custom-integrated circuits were designed to 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.
“Because we can actually stimulate and record in the same brain region, we know exactly what is happening when we are providing a therapy,” said Muller, in a statement.
WAND is both wireless and autonomous, meaning that once it learns to recognize the signs of a 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.
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 in Nature Biomedical Engineering.
The research 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, 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.”
Cortera Neurotechnologies has filed a patent application on the integrated circuit used in this work.