November 09, 2003
Brain-computer interfaces
New research into how signals from the brain can be captured by a computer or other device to carry out an individual’s command may allow people with motor disabilities to more fully communicate and function in their daily lives.
Brain-computer interfaces (BCIs) using new wireless technology have shown advances in BCI-based movement control. Research in technologies for obtaining brain signals for BCI applications has led to the development of implantable BCI devices that could be used by people with severe motor disabilities.
Groundbreaking work conducted by Douglas J. Weber, PhD, at the University of Alberta, Edmonton, Canada, and his colleagues has led to the development of an implantable microelectrode array that can record neural sensory responses resulting from movements of the leg. The investigators have developed an analysis technique that allows accurate prediction of leg positions from the patterns of recorded neural activity.
The technique relies on the fact that multiple sensors acting together provide the central nervous system with important feedback for controlling movement. For example, sensors called muscle spindles that are embedded in muscle fibers measure the length and speed of muscle stretch, while other sensors in the skin respond to stretch and pressure. When an individual is paralyzed by injury or disease, neural signals from these sensors cannot reach the brain, and thus cannot be used to control motor responses. Paralysis also keeps neural signals originating in the motor regions of the brain from reaching the muscles.
The work of Weber and his colleagues shows that it is possible to extract feedback information from the body’s natural sensors that could then be used to control a prosthetic device, allowing an individual to regain some command and control of his or her own movements.
A sterile surgical procedure is used to implant arrays of 36 microelectrodes into the dorsal root ganglion, part of the spinal nerve that contains the nerve cell bodies that house these natural sensors. Historically, it was difficult to record from these sensors because their cell bodies are located in this difficult-to-reach nerve bundle entering the spinal cord. The wires from the microelectrode array are led out through the skin to a small electrical conductor. The procedure allows simultaneous recordings from many sensory nerves during normal motor activities such as walking. A digital camera tracks the position of the leg, and a mathematical analysis relates the sensory activity to leg movement. The investigators found that fewer than 10 neurons are needed to accurately predict the path of the leg. This finding is encouraging because it suggests that a small number of neurons could provide the feedback signals needed to control a prosthetic device.
Other investigators are developing wireless devices for recording neural activity. Groups from Brown University in Providence, R.I., and the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., have both developed wireless implantable devices that use advanced microelectronic technology that eliminates the shortfalls of currently available neural recording systems.
These results are being presented at the Society for Neuroscience 2003 Annual Meeting.