June 2019 create digital
Future medical devices could cut out the need for external interventions by using the body’s own electrical signals to predict problems and help the nervous system keep them in check. Almost all bionic ear, bionic eye, epilepsy control and brain-computer interface devices must be tuned by a medical specialist to deliver the right level of electrical stimulation to patients’ nervous systems. This is known as open-loop control. Closed-loop control systems allow devices to tune themselves in response to electrical signals produced by the patient’s body.
For example, a bionic ear could automatically adjust stimulation levels to control the volume heard by a patient, or an implant could monitor brain activity for signs of an impending seizure and stimulate the brain in a way that steers it away from the seizure state. “Our own bodies have these closed-loop control systems, but these systems can fail with disease or injury, which is why an artificial system is so appealing,” said Professor David Grayden, an electrical and electronic engineer and computer scientist based in the University of Melbourne’s biomedical engineering department.
As the son of a linguist, Grayden developed an early fascination with the mechanics of language. So much so, that during his electrical engineering degree he took linguistics as a non-technical elective. He later combined the two disciplines during a PhD in speech recognition using artificial neural networks. This flowed into a fellowship at the Bionics Institute, where Grayden developed sound processing strategies for cochlear implants to help bionic ear users understand speech in noisy environments.
He now focuses on understanding the language of the nervous system, which uses electrical signals to communicate what is happening in the body. Like spoken language, the nervous system has a wide range of dialects. Grayden said that one of the greatest challenges faced by medical bionics researchers is the complexity of the human brain and nervous system, which can vary greatly between patients. “A stimulation strategy for one person might be completely inappropriate for another who has the same condition,” he explained.
