Getting a good look inside the brain would be an enormous help to doctors who treat conditions such as epileptic seizures. But despite advances in scans, the only way to really see which neurons are firing is to take direct measurements of the brain, which involves opening up the skull.
Recent work funded by the National Institutes of Health is addressing that issue with the development of a flexible brain implant. The implant has only been used in cats so far, but it looks promising as a way to get a high-resolution picture of neural firing.
Seizures happen when neurons in certain parts of the brain — the regions differ among cases — start firing all at once. Drugs can alleviate the symptoms, but some people need to have a piece of their brain removed to stop their seizures. To do that surgery correctly, doctors need an accurate picture of which neurons are sending the wrong signals. Current methods involve implanting sensors that are as much as a centimeter apart and up to 5 millimeters across.
A patient's brain with the currently used type of electrodes attached for monitoring. Image courtesy of Brian Litt.
The new device is an array of interconnected sensors, only 25 microns thick, with 360 electrodes in every square centimeter. The electrodes are spaced only a half millimeter apart and could be made even smaller, said Brian Litt, associate professor of neurology and bioengineering at the University of Pennsylvania and one of the researchers involved in the study. “Usually any medical device that’s electrical has wires going to a 'can,'” he said. “One of the big inventions here is active processing.” That means the implant can do a lot of the signal processing on-site rather than send the data elsewhere.
Another advance is the ability to network the sensors, similar to the way they are set up in a digital camera. (Litt credits Jonathan Viventi, an assistant professor of electrical and computer engineering at the Polytechnic Institute of New York University, who helped lead the research team, with the inspiration).
Litt said he hopes to scale up the technology and pack in more sensors, eventually building devices that will be able to both sense and stimulate regions of the brain. Beyond treating epilepsy, they could be used for interfacing with artificial limbs and applying stimulation where needed for some neurological disorders.
Image: National Institutes of Health.