SEMINAR

Neural Interface Technologies for Human Brain

Youngbin Tchoe

Department of Biomedical Engineering
Ulsan National Institute of Science and Technology (UNIST)

Electrophysiological devices are critical for mapping eloquent and diseased brain regions and therapeutic neuromodulation in clinical settings and are extensively utilized for research in brain-machine interfaces. However, the existing devices are often limited in either spatial resolution or cortical coverage, even including those with thousands of channels used in animal experiments. Here, we developed scalable manufacturing processes and dense connectorization to achieve reconfigurable thin-film, multi-thousand channel neurophysiological recording grids using platinum-nanorods (PtNRGrids). With PtNRGrids, we have achieved a multi-thousand channel array of small (30 μm) contacts with low impedance, providing unparalleled spatial and temporal resolution over a large cortical area. The 7” long cortical electrodes together with our sterilizable compact connector overcome challenges associated with the required large separation between the sterile surgical field and the non-sterile acquisition electronics enabling reliable intraoperative recordings from patients undergoing neurosurgical resections.

In the clinical setting, PtNRGrids resolved fine, complex temporal dynamics from the cortical surface in an awake human patient performing grasping tasks. High gamma activities (HGAs) showed distinctive neural correlates of hand movements when compared to baseline. Furthermore, we recorded phase reversal boundaries during motor mapping to precisely localize the central sulcus in sub-mm scale resolution. These results with our high-density grids offer an unprecedented view of the functional organization and coordination of motor function over large brain regions in the human cortex. Additionally, the PtNRGrids identified the spatial spread and dynamics of epileptic discharges in a patient undergoing epilepsy surgery at 1 mm spatial resolution, including activity induced by direct electrical stimulation. These findings demonstrate the power of the PtNRGrids to transform clinical mapping and research with brain-machine interfaces and highlights a path toward novel therapeutics.

Furthermore, we integrated a flexible micro-LED display technology with PtNRGrids to provide automated and real-time feedback directly from the cortical surface for efficacious and high-precision neurosurgery. Flexible gallium nitride micro-LEDs with thousands of pixels were combined on the backside of the PtNRGrids to make a transparent LED+ECoG grid which could record the cortical activities, process the data in real time, and display brain mapping information on the cortical surface. On top of the pig’s brain, the LED+ECoG grid precisely displayed the functional boundary between the motor and sensory cortices, localized HGAs under the sensory stimulus, and the propagation of interictal discharges induced by epileptogenic neurotoxin. By providing direct and immediate feedback of the boundary between healthy and pathological tissues to the operating neurosurgeon, this technology has the potential to significantly shorten surgical time and enhance the precision of resective neurosurgery. The real-time brain mapping information displayed on the LED+ECoG grid can help surgeons accurately identify the functional boundaries of brain regions and determine the optimal area to remove tissue, reducing the risk of damage to healthy brain tissue.