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With potential to one day help people with brain or spinal injuries move or communicate, the brain-computer interface (BCI) system was developed by researchers at Brown University in Rhode Island.
BCI systems use implantable sensors that record electrical signals in the brain and use those signals to drive external devices like computers or robotic prosthetics. Most current systems use one or two sensors to sample up to a few hundred neurons, but neuroscientists are interested in systems that can gather data from much larger groups of brain cells.
The new wireless neurograins, each about the size of a grain of salt, independently record electrical pulses made by firing neurons and send the signals wirelessly to a central hub, which co-ordinates and processes the signals.
The researchers used 48 neurograins to record neural activity in a rodent. They said the results could lead towards a system that enables detailed recording of brain signals, leading to new insights into how the brain works.
“One of the big challenges in the field of brain-computer interfaces is engineering ways of probing as many points in the brain as possible,” said Professor Arto Nurmikko, the study’s senior author. “Up to now, most BCIs have been monolithic devices — a bit like little beds of needles. Our team’s idea was to break up that monolith into tiny sensors that could be distributed across the cerebral cortex. That’s what we’ve been able to demonstrate here.”
The first part required shrinking the complex electronics involved in detecting, amplifying and transmitting neural signals into the tiny silicon neurograin chips. The team designed and simulated the electronics before going through several fabrication iterations to develop operational chips.
The second challenge was developing the external communications hub that receives signals from the chips. The device is a thin patch, about the size of a thumb print, that attaches to the scalp outside the skull. It works like a miniature cellular phone tower, employing a network protocol to co-ordinate the signals from the neurograins, each of which has its own network address. The patch also supplies wireless power to the neurograins, which are designed to operate using a minimal amount of electricity.
“This work was a true multidisciplinary challenge,” said lead author Jihun Lee. “We had to bring together expertise in electromagnetics, radio frequency communication, circuit design, fabrication and neuroscience to design and operate the neurograin system.”
The team also tested the devices’ ability to stimulate the brain as well as record from it, using tiny electrical pulses to activate neural activity. The stimulation is driven by the same hub that co-ordinates recording and could one day restore brain function lost to illness or injury, researchers hope.
The size of the rodent’s brain limited the researchers to 48 neurograins for this study, but they ultimately aim for systems with ‘many thousands’ of chips.
The research was published in Nature Electronics.
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