A Visualization Microdisplay for Neuronal Activity on the Brain Surface Using Electroencephalography

Background Introduction

Current functional mapping in neurosurgery primarily relies on verbal communication between neurosurgeons and electrophysiologists. These processes are time-consuming and have limited resolution. Additionally, the electrode grids used to measure brain activity have low resolution and do not sufficiently conform to the brain surface. To more effectively monitor and display neuronal activity on the brain surface in real-time during surgery, this study proposes and develops a micro-electrophysiological display (iEEG microdisplay) with 2048 gallium nitride (GaN) light-emitting diodes (LEDs).

Research Overview

This paper, authored by Youngbin Tchoe and others, belongs to various departments at the University of California, San Diego, including the Department of Electrical and Computer Engineering, the Department of Bioengineering, the Department of Anesthesiology, the Department of Neurosurgery, among others. The paper was published on April 24, 2024, in Science Translational Medicine.

Research Workflow

Experimental Design and Methods

This study integrates multiple phases of experiments, including the selection of experimental animals (rats and pigs), the construction and validation of the display, and the detection of electrophysiological signals under various stimulation and pathological models.

Display Construction

The developed iEEG microdisplay embeds 2048 GaN μLEDs in an ultra-thin polyimide layer. GaN μLEDs were chosen for their high efficiency and low power consumption, capable of providing high-intensity light output in bright surgical environments while generating minimal heat. The display uses quantum dot color conversion technology, enabling the display to emit multiple colors, enriching the visual representation of brain activity patterns.

Construction and Validation

To construct the display, a combination of the GaN μLED array and platinum nanorod (PtNR) mesh was used, followed by a series of experiments for validation. These experiments included checking temperature changes and thermal effects on brain tissue, and verifying the electrical safety of the display. Results showed that the display maintained a relatively stable temperature during operation, causing no significant damage to the brain tissue.

Experimental Results

Detection of Functional Cortical Boundaries

Using rat and pig models, the study utilized different colored LEDs to display functional cortical boundaries in real-time during surgery, particularly focusing on the motor cortex (M1) and somatosensory cortex (S1).

Identification of Individual Cortical Columns

Through local sensory mapping, the research team applied electrical and air-puff stimulation to the pig’s face and limbs, successfully displaying local high-gamma responses (HGA) in real-time. These experiments indicate that the iEEG microdisplay has the capability to display cortical columns and corresponding brain region activities.

Display of Electrical Stimulation Responses

Using bipolar probes and stereoelectroencephalography probes to conduct deep brain electrical stimulation on pigs, the display successfully showed real-time potential distribution maps of electrical stimulation responses.

Dynamic Monitoring of Pathological Activities

Using epileptiform activities induced by different neurotoxins (e.g., Bicuculline and 4-Aminopyridine), the display was able to show pathological wave dynamics, monitoring the onset and spread of seizures in real-time.

Conclusion and Significance

This study demonstrates the potential of the iEEG microdisplay in real-time visualization of cortical activity, significantly improving the precision and efficiency of neurosurgical operations. With high-resolution real-time visual feedback, the iEEG microdisplay is expected to replace existing brain functional mapping techniques, enhancing the accuracy and safety of neurosurgical procedures.

Research Highlights

1. Proposed a novel real-time iEEG microdisplay technology, providing high-resolution and highly visualized cortical activity mapping.
2. Successfully combined GaN μLED with PtNR mesh, offering colorful visual representation, achieving real-time dynamic monitoring in surgical settings.
3. Showed promising application prospects in handling pathological wave dynamics, aiding in the precise identification of functional and pathological brain regions during surgery.

Future Applications and Prospects

The iEEG microdisplay developed in this study offers potential technological advancements for future neurosurgical operations and basic neuroscience research. Future directions for improvement include: - Further reducing noise interference to improve display quality; - Increasing full-color display capabilities to further enhance visual effects; - Conducting tests and validations for human applications to ensure clinical safety and efficacy.

This study provides a new technical means for brain functional mapping and intraoperative neurological monitoring, showing broad clinical and research application prospects.