UC Berkeley researchers have developed a wireless, autonomous, closed-loop neurostimulator that sits outside the head, monitoring electrical activity in the brain and intervening with electrical stimulation to ward off seizures. The device, which the team has called WAND (Wireless, Artifact-free Neuromodulation Device), can record activity at up to 128 points in the brain, and is designed to quickly learn and refine its model of the kinds of signals that precede tremors or seizures in each patient.

Importantly, as the device is a closed-loop system, it's able to record activity in the brain even as it fires electrical stimulation back into it, which makes the device incredibly quick and effective in determining what kinds of stimulation are most effective in stopping seizures and other events in their tracks. It can take years for doctors to fine-tune a system without real-time feedback like this.

Closed-loop stimulation therapies are extremely difficult to achieve, because you're trying to measure very small electrical fluctuations from the brain while blasting it with much larger electrical pulses from the stimulators. The Berkeley team compares this challenge to trying to measure small ripples in a pond while splashing with your feet.

But researchers at Cortera Neurotechnologies managed to design an integrated circuit capable of measuring the full signal from the brain and the strong pulses from the stimulator, allowing the WAND device to subtract the latter from the former to get a clean signal showing exactly what the stimulation is doing to the brain in real time.

The WAND device sits outside the head, in a custom-built chassis. The team demonstrated it with a study in which rhesus macaques were trained to use a joystick to move a cursor into a box. The device learned the brain patterns that arose before the monkey's arms made a specific movement to use the joystick, then successfully began intervening with neurostimulation to delay that movement, while simultaneously recording brain activity throughout the process. To the researchers' knowledge, it's the first time a closed-loop system has been demonstrated delaying reaction time based on a neurological recording.

The next step is for the researchers to upgrade the WAND system with intelligence that would allow them to experiment with its neurostimulation therapy and refine its own techniques in response to real-time data.

"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," says Cortera's lead researcher Rikky Muller.

Source: UC Berkeley

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