Project Objectives: This is a multi-disciplinary study which aims to develop a fully implantable brain-computer interface system for the restoration of motor function after neurological injuries such as spinal cord injury (SCI) and stroke.
Background: Despite our highly successful development program of an EEG-based BCI-controlled lower-extremity prosthesis for restoration of walking after SCI, it became immediately apparent that the real-world applicability of such a system is limited by the low resolution and quality of the EEG. It also requires bulky external equipment that needs to be donned/doffed through tedious time consuming processes. Addressing these problems would most likely require the use of an implantable BCI system to acquire brain signals with higher resolution and fidelity.
However, two major problems can be observed in the current trend in the development of implantable BCI systems:
- The use of intracortical microelectrode: These electrodes are highly invasive and have a tendency to fail due to factors such as scarring, gliosis, electrode dissolution, and other unknown factors. Hence, they may need to be replaced after a period of months to years.
- Wireless transmission of electrophysiological signals: Transmitting brain signals to an external computer is a high-bandwidth, high power consumption process that leads to a variety of additional problems. First, the wireless transmission of brain signals to an external computer will inherently tether the recipient to this computer to execute the requisite BCI algorithms. Furthermore, the chronic brain exposure to wireless signals may present thermal risks and other unknown oncogenic risks. Environmental noise and interference can also affect BCI performance.
This set of problems stemming from limited longevity due to the signal instability of intracortical microelectrodes as well as limited practicality and safety due to the reliance on wireless transmission of brain signals to an external system makes the current generation of implantable BCIs systems highly unlikely to be adopted in clinical practice. As a result, the goal of our team is to develop a novel, fully implantable system that is clinically applicable, has long term signal stability, and can perform highly accurate on-board signal processing for online BCI operation.
Current Status: The project is now funded by the National Science Foundation (NSF) to develop the ultra-low powered hardware for a fully implantable, ECoG-based BCI system with novel, custom intergrated circuits (designed with nanoscale architecture). Work is underway to design, fabricate, and test these circuits and to develop efficient signal processing algorithms which can be executed in real time on a low-power embedded system to decode motor imagery with high performance.
2013-2014: The project was conceived as a collaboration between myself, Dr. Payam Heydari (UCI EECS), Dr. Zoran Nenadic (UCI BME), and Dr. Charles Liu (Rancho Los Amigos National Rehabilitation Center, Neurosurgery).