Frequently Asked Questions
- Will this device allow persons who are blind to see?
It depends on what is meant by 'see'. When the tongue-based electrotactile array is controlled by an electronic camera, volunteer test subjects have performed certain visual tasks, such as determine the orientation of the upper-case letter 'E' (i.e., is it facing up, down, left, or right). They can perform this task about as well as a person with a visual acuity of 20/830. This means that a person with 'normal' vision (20/20) could perform this task while 830 feet away from the test object, whereas the person using the tongue-based visual prosthesis would have to be only 20 feet away. 20/200 acuity is considered legally blind in many jurisdictions. Our hope is that with technology improvements and a lot of practice by highly-motivated users, some of them may be able to perform certain kinds of simple visual tasks to enhance their independence. This will likely be many years in the future. Persons who are blind are not likely to trade in their long canes or guide dogs anytime soon as a result of this technology.
- If someone is born blind, would they be able to benefit from this device? Would they be able to determine what they are seeing? Is depth perception possible?
- How new is this technology?
The concept of sensory substitution (using one sense, such as touch, to receive information normally received from another sense, such as vision) is quite old, probably over one hundred years. Serious scientific study with useful electronic technology began in the early 1960's, culminating with devices that allowed practiced test subjects to identify ordinary household objects such as telephones and watering pitchers, when these were scanned using a video camera in a well-lit, high-contrast environment. They were also able to experience uniquely visual concepts like looming (apparent increase in size with decreasing distance) and perspective (apparent change in shape with changing points of view). In this case, tactile stimulation was presented to the back or abdomen. This early work is summarized in a book by Paul Bach-y-Rita, Brain Mechanisms in Sensory Substitution, Academic Press, 1972.
Although we have references as early as 1919 (German Patent 326283 byu Ludwig Machts, describing a tongue-based vision substitution device), the use of the tongue to receive dynamic, updatable touch information in a safe, practical manner had received scant attention until October, 1998, when we published an article in the Journal of Rehabilitation Research and Development, vol. 35, no. 4, pp. 427-430. This article demonstrated that perception of simple geometric patterns was possible when they were presented to the tongue with electrical stimulation of the sense of touch.
- Is the device in the mouth called a sensor?
No, in our application it would be called a stimulator or display. Sensors receive information; examples are cameras and microphones. Stimulators deliver information; examples are television screens and loudspeakers. The in-mouth electrode array as we currently use it delivers information to the tongue, although one might envision adding switches to the device to allow it to receive information as well, information that could be used to control other devices such as a computer.
- Are other groups working on this or similar technology?
- US Patent 5,878,154 by W. Schimmelpfennig describes a tongue-based tactile vision substitution device.
- Hui Tang at the University of Missouri-Columbia is developing ultra-flexible electrode arrays for tactile display to the roof of the mouth.
- Wicab, Inc., founded in 1998 by Dr. Bach-y-Rita, is commercializing the technology.
- How soon could tongue-based information display be practical?
Vestibular feedback for persons with balance disorders has been commercialized, please contact Wicab, Inc. for further information. More complex applications such as navigational or directional information for search-and-rescue personnel could follow. Practical visual prostheses are more complex and will take longer.
- How did the tongue display technology come about?
We (Bach-y-Rita, Kaczmarek, Tyler) have been working on fingertip-based electrotactile computer graphics displays since 1992. One day Bach-y-Rita and Kaczmarek decided to try licking the electrode array that we use for fingertip display research. We discovered that the quality of electical stimulation was quite good, was easier to control than on the fingertips, and that we could identify simple spatial patterns. We subsequently tested several volunteers and found out that they, too, could perceive electrotactile patterns on their tongues. These results are published.
In retrospect, these results might be expected. The cortical representation (the part of the brain's cerebral cortex) responsible for processing touch information from the tongue is quite large, similar to the hands. One might therefore expect the tongue to be a good site for tactile information display. Bach-y-Rita, in fact, suggested this years ago, although the instrumentation did not yet exist to test the idea.
We have subsequently designed better instrumentation and have been exploring potential applications for this generic technology, as well as trying to understand the basic perceptual properties of electrotactile display on the tongue.
- What does the future hold?
We hope to miniaturize the entire tongue stimulation apparatus so that it fits into a small mouthpiece similar to a dental retainer, with the tongue electrode array, stimulation circuitry, and batteries self-contained. An FM radio receiver incorporated into the retainer would receive data from an external source, so that no wires would need to go into the mouth. This miniaturization is technically feasible and represents an engineering rather than a scientific challenge. The level of integration and miniaturization is similar to what might be expected for a small cardiac pacemaker, which also contains batteries, stimulation circuits, and data communications. As for applications, we aim for nothing less than transformation of what is meant by "human-machine interface." Future directions are detailed in the following articles:
- Bach-y-Rita, P., Kaczmarek, K. A. and Meier, K. (1998). The tongue as a man-machine interface: A wireless communication system. Proc. Int. Symp. Info. Theory & Apps. pp. 79-81.
- Bach-y-Rita, P. and Tyler, M. E. (2000). Tongue man-machine interface. Medicine Meets Virtual Reality Conf. pp. 17-19.
- Bach-y-Rita, P., Tyler, M. E. and Kaczmarek, K. A. (2003). Seeing with the brain. Int. J. Hum. Comp. Interact. 15, 285-295.
- Bach-y-Rita, P., Kaczmarek, K. A. and Tyler, M. E. (2003). A tongue-based tactile display for portrayal of environmental characteristics. In Virtual and Adaptive Environments (Hettlinger, L. J. and Haas, M. W., Eds.), pp. 169-186. Erlbaum, Mahwah, NJ.
- Bach-y-Rita, P. and Kercel, S. W. (2003). Sensory substitution and the human-machine interface. Trends in Cogn. Sci. 7, 541-546.
In parallel, we will continue to study the perceptual characteristics of electrical stimulation of touch on the tongue and how to best code information for specific applications. This is one of the most exciting and challenging aspects of our research, the results of which will ultimately determine the real-world practicality of tactile information display using the tongue.
- What is the intellectual property status of this technology?
This technology is patented, Tongue-placed tactile output device, US Patent 6,430,450. Contact the Wisconsin Alumni Research Foundation.
- Can I buy, rent, or license a tongue display apparatus?
Please see our contact page.
For one commercial version of the technology for balance or vision applications, please contact Wicab, Inc.
As Paul Bach-y-Rita said frequently, “You see with your brain, not with your eyes.” Is tactile vision "seeing?" That's a philosophical question, often called called the Molyneux question (Google it). Experienced tactile vision users regularly make judgments of object distance, relative size, and position in order to navigate through a physical environment or to perform coordinated hand-'eye' tasks such as reaching and grasping an object. They are able to distinguish between self-motion and object motion and appreciate the effects of looming, parallax, perspective, and visual flow fields. Users also experience distal attribution, meaning they perceive objects as being "out there", that is, in front of the camera -- not just a sensation on their tongues. Tactile vision, however, presently lacks sufficient detail for most everyday tasks and is typically tested in well-controlled, high-contrast, laboratory environments. There are significant problems with complex visual environments. We are not aware than anyone has ever crossed a street with a tactile vision system. Yet.