In a paper published today in Nature Nanotechnology, the researchers report on successful tests of their new probes in rodents.

The researchers say the ability to record and map the full range of brain signals using electrophysiological probes will greatly advance our understanding of brain diseases and aid the clinical management of patients with diverse neurological disorders. However, current technologies are limited in their ability to accurately obtain with high spatial fidelity ultraslow brain signals.

Co-lead author Dr Rob Wykes (UCL Queen Square Institute of Neurology and University of Manchester) said: “Epilepsy is the most common serious brain disorder worldwide, and many people do not benefit from drug treatments and thus require surgery. As the surgery needs to be precisely targeted, it is vital to be able to accurately pinpoint where a person’s seizures originate.

“Our technology is able to clearly map a wide range of brain signals with very high resolution, so we hope it could enable more effective epilepsy surgery, which could also be done by removing less brain tissue.”

The international team led by researchers at UCL, the Catalan Institute of Nanoscience and Nanotechnology (ICN2), and the Institute of Microelectronics of Barcelona (IMB-CNM-CSIC) report on a probe they have developed which is capable of recording the full spectrum of brain signals.

Epilepsy remains difficult to treat, as up to 30% of people are unable to control their seizures using traditional anti-epileptic drugs. For those who do not benefit from medication, epilepsy surgery may be a viable option. Surgical removal of the area of the brain where the seizures first start can put a stop to seizures; however, the success of surgery relies on accurately identifying the seizure onset zone.

Epileptic brain signals span over a wide range of frequencies – much larger than the band monitored in conventional electroencephalogram (EEG). Electrographic biomarkers of a seizure onset zone include very fast oscillations as well as infraslow activity (electrical oscillations in the brain with very low frequency) and direct-current (DC) shifts. Infraslow oscillations can provide very relevant information associated with seizure onset but are seldom used due to the poor performance of current probes to record these types of slow brain signals. Application of this technology will allow researchers to investigate the role infraslow oscillations play in promoting susceptibility windows for the transition to seizure, as well as improving detection of clinically relevant electrophysiological biomarkers associated with epilepsy.

The graphene depth neural probe (gDNP) developed by the research team consists of a millimetre-long linear array of micro-transistors imbedded in a micrometre-thin polymeric flexible substrate. The flexible gDNP devices were chronically implanted in rats and mice used as models of seizures and epilepsy. The implanted devices provided outstanding spatial resolution and very rich wide bandwidth recording of epileptic brain signals over weeks. In addition, further tests confirmed no significant tissue damage and neuro-inflammation, attributed to the biocompatibility of the used materials, including graphene, and the flexible nature of the gDNP device.

Once this technology progresses to human trials and clinical use, it may enable surgeons to identify and confine much more precisely the zones of the brain responsible for seizure onset before surgery, leading to less extensive resections and better outcomes. Ultimately, this technology may also be applied to improve our understanding of other neurological diseases associated with ultraslow brain signals, such as traumatic brain injury, stroke and migraine.

This study was led by researchers at UCL and the ICN2 and IMB-CNM-CSIC in Spain, alongside co-authors at the University of Manchester, the Universitat Autònoma de Barcelona (Spain) and g.tec medical engineering GmbH (Austria).

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  • Design reflecting the probes and registered signals