A team of researchers from New York and Beijing have developed a conformable neural interface device that can be wrapped around the brain and used to monitor local field potentials (LFPs) and action potentials from the cortical surface.
The cellophane-like device – called a NeuroGrid – is now being used in human trials for the first time. While the trials are still at the early stages, the device is proving effective on human patients. Should the trials continue to prove successful, the device could be a huge breakthrough for treating patients suffering from epilepsy.
There are approximately 2.9 million individuals in the United States with active epilepsy. While drugs can be used to prevent seizures in certain patients, some individuals do not respond to the drugs. When drugs cannot be used to control the disease, surgery is required. While it is possible to perform surgery on parts of the brain where the seizures begin, identifying targets can be difficult.
Prior to surgery, doctors use electrocorticography (ECoG) technology to monitor brain activity in patients for several days. The technique is invasive and has only been used to record broad patterns of brain activity. For more precise measurements, doctors need to insert electrodes into the brain tissue.
These techniques naturally have numerous drawbacks, yet an alternative method for monitoring brain activity has not been developed. However, the NeuroGrid promises to change that. The 4-micrometer thick cellephane-like membrane is made from a polymer called parylene that has already been shown to be clinically safe to use in humans. The wrapper fits over the surface of the brain and conforms to the contours. The membrane contains 120 conductive polymer electrodes that record brain activity and the device can be used to cover 420 mm2 of the neocortex. Wires connect groups of 10 electrodes to a single chip and the recordings are sent to a computer for analysis.
When fitted, the device can be used to obtain precise recordings from the cortical surface of the brain without the use of brain-penetrating electrodes. The NeuroGrid is also sensitive enough to monitor the activity of single neurons, although doing so is a challenge.
Trials in rats have been successful, although the technology has only just been used for a clinical trial on humans. The NeuroGrid was fitted to five patients prior to surgery to monitor the effectiveness of the technology.
The NeuroGrid may be many years away from clinical use, although the results of the limited human trial have been promising. The team is now looking to decrease the size of the Neurogrid and reduce the number of wires required. It is hoped that further development of the membrane will allow doctors to use multiple grids to obtain precise measurements from larger areas of the neocortex to obtain detailed data to guide surgery.