NEUROSENSING
Reconnecting a prosthetic device to the human neurological system represents another major step in replacing lost function. This type of intervention is already proving successful in enabling the user of such a device to regain voluntary control over the prosthesis at a neurological level, instead of having to manipulate the prosthetic function solely by means of joint mobility and muscular activity.
Over recent decades, much research has been undertaken in the quest to better understand neural activity, with the objective of restoring anatomical function after paraplegia, spinal cord injury or amputation. This fast-evolving concept is one of small electrodes that will pick up electrical activity from a nerve. These signals will be interpreted by an Artificial Neural Network that recognizes patterns in the activity. A cornerstone of such research is the establishment of durable and sensitive connections with the body’s nerves.
Neurosensing poses two major challenges. Firstly, the implant must be accepted by the body tissue and have the necessary stability for long-term use. The other challenge is to successfully obtain reliable and useful recording and stimulating characteristics from a high number of the primary transmission lines of the body’s nervous system simultaneously. It is along these lines, or axons, that electrical impulses are conducted. These axons are microscopic in diameter but can sometimes be quite lengthy – like the sciatic nerve which runs from the base of the spine to the big toe in each foot.
Already implants have been used in short-term tests to extract and interpret sensory neural signals. The signals from many nerve axons have been mapped and identified in relation to different tasks such as muscle activity, the movement of limbs and senses like touch or pressure.
In the control of an artificial motorized arm, nerve signals have been “re-wired” to a muscle, allowing the muscle to work as an amplifier to extract nerve activity that was then interpreted at certain arm movements. One of Össur’s partners, Victhom Human Bionics Inc., has been granted a patent for a signal amplifying circuit for electroneurographic recording. This invention is a significant technological advancement in the field of neurostimulation and more specifically in neurosensing.