Reverse Engineering Proprioception: Development of a biomimetic neuroprosthesis to restore a sense of limb movement
Abstract:
We have developed a brain machine interface (BMI) that allows monkeys to pick up and move objects despite a peripheral nerve block causing complete paralysis of the flexor muscles below the elbow. Such a system might ultimately provide spinal cord injured patients with control of arm and hand movements through normal cognitive processes. However, a major issue to be addressed in the development of more effective BMIs is restoring the somatosensory feedback that is also lost in spinal cord injury. Proprioception is essential for normal movement. Its loss largely eliminates the ability to plan movement dynamics or to make rapid corrections to limb perturbations. Although some progress has been made toward restoring touch through intracortical microstimulation (ICMS), there has been as yet, little corresponding success for proprioception.We have embarked on a series of experiments designed to generate naturalistic sensations of limb movement by using ICMS to recreate natural patterns of activity in the primary somatosensory cortex (S1). Neurons in area 2 of S1 signal limb movement with discharge that is tuned to both the direction and speed of hand movement. By stimulating groups of electrodes that have similar directional tuning, we have succeeded in inducing perceptions of limb motion that appear to be similar to those induced by actual limb movement. However, in addition to velocity tuning, these neurons are related to the position of the limb and its interaction forces with the environment. Furthermore, although we and others represent the tuning as though it is in hand-centered coordinates, we now have evidence that it may be closer to muscle coordinates. If we are to be successful in mimicking natural proprioception, we will need methods capable of capturing the full extent of these multi-modal neural representations of limb state, and replicating them through spatiotemporal modulation of multi-electrode ICMS.
Biography:
Lee E. Miller is a Distinguished Professor of Neuroscience in the Departments of Physiology, Physical Medicine and Rehabilitation, and Biomedical Engineering at Northwestern University. He received the B.A. degree in physics from Goshen College, Goshen, IN, in 1980, and the M.S. degree in biomedical engineering and the Ph.D. degree in physiology from Northwestern University in 1983 and 1989, respectively. He completed two years of postdoctoral training in the Department of Medical Physics, University of Nijmegen, The Netherlands. He was inducted into the American Institute for Medical and Biological Engineering in 2016, and is the current president of the Society for the Neural Control of Movement.
Dr. Miller has had a career-long interest in the motor and sensory signals that are generated by single neurons in the brain during arm movement. His early work was devoted to studying these signals in the brainstem, cerebral cortex, and cerebellum, and their relation to muscle activity. In the past 10 years, Dr. Miller’s lab has increasingly focused on translational research, pioneering the use of brain machine interface technology in projects aimed at restoring movement and sensation to paralyzed patients. His interdisciplinary approach has led to productive collaborations locally, nationally, and internationally. He has authored over 100 manuscripts, book chapters, and review articles.