A new, ultrathin, ultraflexible implant loaded with sensors can record the electrical storm that erupts in the brain during a seizure with nearly 50-fold greater resolution than was previously possible. The level of detail could revolutionize epilepsy treatment by allowing for less invasive procedures to detect and treat seizures. It could also lead to a deeper understanding of brain function and result in brain-computer interfaces with unprecedented capacity.
For epilepsy patients who don’t respond to medication, neurologists will often try to map where in the brain the seizure originated so that region can be surgically removed. The doctor removes a section of skull and places a bulky sensor array on the surface of the patient’s frontal cortex.
“These clinical devices haven’t changed much since the ’50s or ’60s,” says Brian Litt, an epilepsy specialist and bioengineer at the University of Pennsylvania and one of the scientists who led the new research. Because the device has to accommodate wires for each electrode, it only has space for fewer than 100 electrodes and gives a poor resolution picture of the electrical activity. “It’s like trying to understand what’s going on in a crowd in Manhattan with a single microphone suspended from a helicopter,” Litt says.
Current technology has stalled out at a sensor array with about eight sensors per square centimeter; the new array—built in collaboration with John Rogers, a professor of materials science and engineering at the University of Illinois Urbana-Champaign—can fit 360 sensors in the same amount of space. To create a small device so densely packed with sensors, Rogers integrated electronics and silicon transistors into the array itself, drastically reducing the amount of wiring.
“This is more like an array of 360 microphones, lowered closer to the surface and recorded from much smaller regions: a couple of people at the street corner, a couple by the mailbox,” Litt says. “This new technique could be the key to understanding functional networks in the brain, and could even be the key to treating and potentially curing some diseases.”
In their first test of the device, on a cat with epilepsy, Litt, Rogers, and graduate student Jonathan Viventi (now an assistant professor studying translational neuroengineering at New York University), saw something striking: a storm of activity that looked like a self-propagating spiral wave. The pattern, only apparent with incredibly high-resolution recording, is remarkably similar to one seen in cardiac muscle during a life-threatening condition called ventricular fibrillation.
Rather than large sections of the brain being responsible for seizures, something Litt says has traditionally been thought to occur, it appears to instead stem from multiple clusters of very small areas, or “microdomains,” in the cortex. The research was published online last week in Nature Neuroscience.