Tiny implant ‘speaks’ to the brain with LED light
A new brain-machine interface (BMI) uses light to “talk” to the brain, experiments on mice show.
The minimally invasive wireless device, placed under the scalp, receives information in the form of light patterns, which are then transmitted to genetically modified neurons in the brain tissue.
In the new study, these neurons fired as if responding to sensory information coming from the mice’s eyes. Mice learned to match these different patterns of brain activity to perform specific tasks, including discovering the location of delicious snacks in a series of laboratory experiments.
The device marks a step toward a new generation of BMIs that will be capable of receiving artificial inputs – in this case, LED light – independent of the typical sensory channels that the brain relies on, such as the eyes. This would help scientists build devices that interface with the brain, without requiring trailing wires or bulky external parts.
“This technology is a very powerful tool for doing basic research,” and it could solve human health problems in the long term, said John Rogersbioelectronics researcher at Northwestern University and lead author of the study, published Dec. 8 in the journal Natural neuroscience.
Bypass the sensory system
The device, which is smaller than a human index finger, is soft and flexible, so it adapts to the curvature of the skull. It includes 64 tiny LEDs, an electronic circuit that powers the lights, and a receiving antenna. Additionally, an external antenna controls the LEDs using near-field communications (NFC) – electromagnetic fields for short-range communications, as is the case for contactless card payments.
The compact device is designed to be placed under the skin rather than being implanted directly into the brain. “It projects light directly onto the brain [through the skull]and the brain’s response to this light is generated by a genetic modification in the neurons,” Rogers told Live Science.
Brain cells do not normally respond to light shining on them, so genetic modification is necessary for this to happen.
“Genetic modification creates light-sensitive ion channels,” Rogers explained. When activated by light, these channels allow charged particles to flow into brain cells, triggering a signal that is then sent to other cells. “Through this mechanism, we create light sensitivity directly in the brain tissue itself,” he said. Genetic modification of brain cells was carried out using a viral vector, a harmless virus designed to deliver the desired genetic modification into specific cells in different regions of the brain.
The use of light to control the activity of genetically modified cells is called optogeneticsand it is a relatively new science. In previous worksThe researchers used a similar approach to activate a single group of brain cells, but the new device allowed them to change the activity of many neurons in the brain.
“[The genetic modification] “It’s as if we can project a series of images – almost as if we were playing a movie – directly into the brain by controlling [the] pattern sequence. »
The researchers tested the implant on mice by wirelessly instructing it to produce various patterned bursts of light. The mice were trained to respond to each pattern with a specific behavior, indicating that they could distinguish the transmitted patterns. For each type of signal, they had to go to a specific cavity in a wall and, if they chose correctly, they received sugar water as a reward.
Well hea neuroengineering researcher at Carnegie Mellon University who was not involved in the study, called it a new technique for using light to tune circuits throughout the brain. “This could have various applications in neuroscience research using animal models… and beyond,” he said.
For example, researchers see the potential of this device in future prostheses. Applications could include adding sensations, such as touch or pressure, to prosthetic limbs, or sending visual or auditory signals to visual or hearing prostheses.
“Optogenetic techniques are just beginning to be used with humans” said Rogers. “There are huge benefits [to using light] because you don’t need to disrupt brain tissue. You can use different wavelengths of light to control different regions of the brain. »
Rogers said that from a technological perspective, the platform could scale to cover much larger areas of the brain and contain more micro-LEDs. However, they would have to rethink the power supply requirements to support a larger device. Technically, it should work in both humans and mice, but more research will be needed before attempting human testing.
“The biggest hurdle is regulatory approval of genetic modification,” he said.
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