Intra vs. extracortical command signals to restore six dimensional hand movements

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DESCRIPTION (provided by applicant): The long-term goal of this project is to restore arm and hand function to people paralyzed below the neck due to a spinal cord injury. New implanted neuroprosthetic devices can now restore arm and hand movements to paralyzed individuals by electrically activating the peripheral nerves. Wheelchair-mounted robotic arms can also provide reach and grasp capabilities to the severely paralyzed. However, one current limitation of these technologies is that the user must be able to convey to the device how they want their arm and hand to move. In people paralyzed below the neck, control options for any assistive device are limited to using retained function from the neck up. Many command options, such as voice commands, tongue-touch keypads, or chin- operated joysticks, can be awkward and can interfere with talking, eating, and normal social interaction. Accessing desired limb movements directly from the brain would allow these people to move their arm and hand just by thinking about doing so while also allowing them to retain normal use of their face and mouth. Two main types of implanted brain recording technologies are being developed and commercialized for chronic human use: 1) small intracortical microelectrodes that are implanted a few millimeters into the brain and can detect the firing activity of many individual neurons, and 2) larger extracortical electrodes that detect the average electrical activity of larger groups of neurons from locations outside the brain. Both types of recording technologies have shown promise as a means to generate movement commands for controlling assistive devices. Intracortical microelectrodes have been used in monkeys and humans to directly control two- and three-dimensional movements of computer cursors and robotic arms. Extracortical brain recordings have also been used in humans to control the two-dimensional movements of computer cursors and robots. The present study will use a monkey model in which each animal receives both types of brain recording technologies in configurations similar to those likely to be commercially available to paralyzed humans within the next five years. Methods will then be developed to translate signals from each type of brain recording technology into the specific movement instructions needed to use the current upper-limb neuroprosthesis systems (i.e. where to place the hand in space, how much to open/close the hand, pronation/supination angle of the forearm, and wrist flexion/extension angle). The speed, accuracy, and stability of the movement commands generated with each type of brain recording technology will be measured. By developing methods for using both brain recording technologies to generate the movement commands needed to control an upper limb neuroprosthesis, this study will move both brain recording technologies forward into practical applications while providing potential users with the performance information they need to weigh these benefits against the inherent risks and decide if either of these implanted brain recording systems is right for them. PUBLIC HEALTH RELEVANCE: Implanted devices are now available that can activate muscles of paralyzed individuals to restore arm and hand movements. The goal of this project is to enable these paralyzed individuals to control the movements of their own arm and hand just by thinking about doing so. This study develops methods for detecting a person's desired movement from the brain using two different types of sensors and then provides potential users with the information they need to decide which type of sensor is right for them.