26th January 2022
Human brain signals in record-breaking resolution
High-resolution recordings of electrical signals from the surface of the brain could improve neurosurgeons' ability to remove brain tumours and treat epilepsy and could open up new possibilities for medium- and longer- term brain-computer interfaces.
A team of engineers, neurosurgeons and medical researchers has published data showing that a sensor array can record electrical signals directly from the surface of the human brain in record-breaking detail. The new device features densely packed grids of either 1,024 or 2,048 embedded electrocorticography (ECoG) sensors. A paper on this advance, led by Professor Shadi Dayeh at the University of California, San Diego (UCSD), is published this month in the journal Science Translational Medicine.
These thin, flexible grids of sensors, if approved for clinical use, would capture brain-signal information directly from the surface of the cortex in 100 times greater resolution than is available today. Access to this highly detailed perspective on which specific areas of tissue are active, and when, could provide better guidance for planning surgeries to remove brain tumours and surgically treat epilepsy. Longer term, the team is working on wireless versions of these ECoG grids that could be used for up to 30 days of brain monitoring for people with intractable epilepsy.
The technology also holds potential for permanent implantation, to improve the quality of life of people who live with paralysis or other neurodegenerative diseases treatable with electrical stimulation – such as Parkinson's disease, essential tremor, and neurological movement disorders.
Today, the ECoG grids most commonly used in surgeries typically have between 16 and 64 sensors, although research grade grids with up to 256 sensors can be custom made. The device created at UCSD is therefore a major advance in the field. It could improve neurosurgeons' ability to remove as much of a brain tumour as possible while minimising damage to healthy tissue. In the case of epilepsy, the higher resolution could enable a surgeon to precisely identify the brain regions where seizures are originating, so that these can be removed without touching nearby regions not involved in seizure initiation. In this way, these high-resolution grids may enhance preservation of normal, functioning brain tissue.
ECoG grids with sensors in the thousands could also help in uncovering a deeper understanding of how the brain functions. Basic science advances, in turn, could lead to improved treatments grounded in enhanced understanding of brain function.
The team at UCSD – who collaborated with Massachusetts General Hospital and Oregon Health & Science University – achieved their breakthrough by packing individual sensors significantly closer to each other, while avoiding problematic interference between nearby sensors. The ECoG grids already in clinical use typically have sensors that are spaced one centimetre apart. But the new 1,024-sensor device has sensors just one millimetre apart, with a total grid area measuring three by three centimetres and is scalable to 2,048 sensors.
The researchers also developed nanoscale platinum rods for recording electrical activity from neurons. The nano-rod shape offers more sensing surface area than flat platinum sensors, giving higher sensitivity and precision. In addition, the sensor grid is thinner and more flexible than today's clinically approved ECoG grids. This allows it to move with the brain; during each heartbeat, for example, when the brain "moves" with the pulsating blood flowing through it, which enables a closer connection and finer signal quality.
During their study, the scientists mapped key regions of the brain in four subjects while they performed motor tasks. They also mapped the cortical column of a rat brain for the first time without the use of a needle and electrical stimulation.
The device's manufacturing process allows for a wide variety of sizes and shapes, which opens up new possibilities for greater and more customised coverage in the future. Scaling up to larger areas and collecting signals from multiple regions simultaneously could unlock more of the brain's mysteries.
For their next step, the team will develop a brain-sensing and brain-stimulating platform to enable treatment of drug-resistant epilepsy. They have been awarded a $12.3 million grant from the National Institutes of Health for their work. This includes funding to make the system wireless, which would be important for implantable grids requiring medium- and longer- term use.
With the goal of getting higher-resolution ECoG grids approved for clinical use, Professor Dayeh and two of his colleagues have also co-founded a startup called Precision Neurotek Inc.
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