Graphene-based implant overcomes technical limitations to record brain activity at extremely low frequencies

The body of knowledge about the human brain is growing exponentially, but questions big and small remain unanswered. Researchers have been using electrode arrays to record the brain’s electrical activity for decades, mapping activity in different brain regions to understand what it looks like when everything is working, and what is happening when it is not.

Until now, however, these arrays have only been able to detect activity over a certain frequency threshold. A new technology developed in Barcelona overcomes this technical limitation, unlocking the wealth of information found below 0.1 Hz, while at the same time paving the way for future brain-computer interfaces.

Developed at the Barcelona Microelectronics Institute (IMB-CNM) of the Spanish Council of Scientific Research (CSIC), and the Catalan Institute of Nanoscience and Nanotechnology (ICN2, a center of BIST and CSIC), and the CIBER in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), and adapted for brain recordings in collaboration with the August Pi i Sunyer Biomedical Research Institute (IDIBAPS), the technology moves away from electrodes and uses an innovative transistor-based architecture that amplifies the brain’s signals ‘in situ’ before transmitting them to a receiver.

Furthermore, the use of graphene to build this new architecture means the resulting implant can support many more recording sites than a standard electrode array, plus is slim and flexible enough to be used over large areas of the cortex without being rejected or interfering with normal brain function. The result is an unprecedented mapping of the kind of low frequency brain activity known to carry crucial information about different events in the brain, such as the onset and progression of epileptic seizures and strokes.

For neurologists this means they finally have access to the brain’s whispered clues. Prof. Matthew Walker, of University College London and world specialist in clinical epilepsy, has called it a ground-breaking technology that has the potential to change the way we record and view electrical activity from the brain. Future applications will give unprecedented insights into where and how seizures begin and end, enabling new approaches to the diagnosis and treatment of epilepsy.

Details of the underlying technological advances (patent pending) can be found in Nature Materials. The development of this technology has been promoted by the Biomedical Applicattions Group at the IMB-CNM, group led by the CSIC scientist Rosa Villa, with Anton Guimerà Brunet as a principal investigator of the project and Eduard Masvidal Codina as the first author of the paper. On the other hand, ICREA Prof. Jose A Garrido has led the research group at the ICN2. The graphene microtransistors were adapted for brain recordings and tested in vivo at IDIBAPS, led by ICREA Prof. Mavi Sánchez-Vives. An imaging technique was developed in collaboration with ICFO, led by ICREA Prof. Turgut Durduran (ICFO is a center of BIST). The project is co-funded by the Graphene Flagship and the BrainCom project.

Article reference:
Eduard Masvidal-Codina, Xavi Illa, Miguel Dasilva, Andrea Bonaccini Calia, Tanja Dragojević, Ernesto E. Vidal-Rosas, Elisabet Prats-Alfonso, Javier Martínez-Aguilar, Jose M. De la Cruz, Ramon Garcia-Cortadella, Philippe Godignon, Gemma Rius, Alessandra Camassa, Elena Del Corro, Jessica Bousquet, Clement Hébert, Turgut Durduran, Rosa Villa, Maria V. Sanchez-Vives, Jose A. Garrido & Anton Guimerà-Brunet. High-resolution mapping of infraslow cortical brain activity enabled by graphene microtransistors. Nature Materials (2018). Published: 31 December 2018. https://www.nature.com/articles/s41563-018-0249-4

Jed A. Hartings. How slow can you go? Nature Materials (2018). Published: 31 December 2018. https://www.nature.com/articles/s41563-018-0272-5