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A wireless 'pacemaker for the brain' could offer new treatment for neurological disorders.
The WAND, developed by engineers at the University of California, Berkeley, can listen to and stimulate electric current in the brain at the same time, potentially delivering 'fine-tuned' treatments for patients with conditions such as epilepsy and Parkinson's.
Scientists say it works like a 'pacemaker for the brain,' monitoring the brain's electrical activity and delivering electrical stimulation if it detects something amiss.
This is hardly the first attempt at such a device, but experts believe this version is the first that can adapt itself to each person's subtle and ever-changing symptoms, that can be hard to detect and hard to stimulate.
Once the WAND 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 the parameters in real-time.
Doctor Rikky Muller, Assistant Professor of electrical engineering and computer sciences at UC Berkeley, said: '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.
'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.'
A device like this could 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, according to the researchers.
WAND - which stands for Wireless Artifact-free Neuromodulation Device - is both wireless and autonomous.
It 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 recognise and delay specific arm movements in rhesus macaques.
They explained that 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.
Dr Samantha Santacruz said: '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,'
Researchers at Cortera Neurotechnologies, led by Dr Muller, designed the WAND custom integrated circuits that can record the full signal from both the subtle brain waves and the strong electrical pulses.
The 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 that type of signal reconstruction impossible.
Dr Muller said: 'Because we can actually stimulate and record in the same brain region, we know exactly what is happening when we are providing a therapy.'
Working with the lab of electrical engineering and computer science Prof Jan Rabaey, the team built a platform device with wireless and closed-loop computational capabilities that can be programmed for use in 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.
Dr Muller said: '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.'
She added: '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.'
The findings were published in the journal Nature Biomedical Engineering.