Tongue drive system revolutionizes assistive devices for disabled

(NC&T/NCSU) And while one might think tongue studs and orthodontic braces are better suited for rebellious teens and bad bites than people with disabilities, the technology they inspired offers spinal cord injury patients an effective, cosmetically acceptable and less invasive method of interacting with the world. Dr. Maysam Ghovanloo, assistant professor of electrical and computer engineering at NC State, has developed the Tongue Drive system an innovative interface that holds promise to be the next generation of assistive devices for people with severe disabilities such as spinal cord injuries or degenerative diseases. The technology takes advantage of the advances in miniature-sized microelectronics, sensors and wireless devices. The basic device consists of three components: a tiny permanent magnet the size of a rice grain, which is coated with gold or platinum and can be attached to the tongue by means of piercing or implantation; a set of very tiny magnetic sensors held in place by brackets on the lower or upper teeth, much like an orthodontic dental retainer; and a control unit. The control unit comprised of sensor interface circuitry, wireless transmitter and a pair of watch batteries is contained in a coin-sized, custom-designed sealed package that rests inside the mouth in the area under the tongue.

"The Tongue Drive system works because the tongue is a flexible manipulating organ with such a wide range of motions within the mouth. The dedicated area to the tongue in the human motor cortex rivals that of fingers," Ghovanloo says. "More importantly, it is connected to the brain via the hypoglossal nerve which usually escapes severe damage in spinal cord injuries. The Tongue Drive system provides maximum capabilities with no invasive procedures and no externally obvious wiring or other visually unappealing components."

Most current assistive devices are switch-based, meaning that commands must be given in sequences by using a switch, such as the sip-and-puff device used by many people with severe disabilities to control wheelchairs. These devices are cosmetically unappealing and tend to be cumbersome and limited in range of capabilities. Other devices, such as head pointers, require a certain amount of musculoskeletal control. There are also Webcam-based devices that scan face or eye movements and require the user to sit in front of the monitor. Recently small arrays of electrodes have been developed that can be implanted in the brain to directly record neural signals and extract users' intentions from their thoughts. However, delicate and highly invasive brain surgery is necessary for these devices to work, and they are very expensive.

Dr. Maysam Ghovanloo's Tongue Drive system promises to give people with severe disabilities an effective, cosmetically acceptable and less invasive technology for interacting with the world. (Photo: NCSU)
The Tongue Drive system uses wireless transmission to communicate with a basic PDA (personal digital assistant) or nearby computer using Bluetooth or Wi-Fi technology. Ghovanloo's team has written software to decode the signals from the mouth sensors, translate them to user commands, and then communicate the commands to the specified device, such as a computer, powered wheelchair, telephone or television. Using the tongue much like a hand on a computer mouse, a person can move the pointer and give complex commands such as "drag-and- drop" or "double-click" with specific tongue movements. When driving a wheelchair, the user can control the wheelchair movements with proportional control, giving the user a smoother, more continuous motion than the stop-and-start motion provided by switch-based devices.

Ghovanloo is collaborating with Elaine Rohlik and Dr. Pat O'Brian at WakeMed Rehab Hospital in Raleigh to test the Tongue Drive prototypes. WakeMed Rehab specializes in rehabilitation for patients with spinal cord injuries, brain injury, stroke and neuromuscular disorders.

"Our goal with this research was to develop a cosmetically appealing and comfortable device that was minimally invasive and that would give a severely disabled person with a spinal cord injury or a degenerative nerve disease the ability to lead a productive and more independent life," Ghovanloo says. "Not only does this device meet this goal, it does so at a very low cost since its components are basically off-the-shelf technology and no surgery is required."

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