The use of a tactile-vision sensory substitution system as an augmentative tool for individuals with visual impairments

The promise of novel technological strategies and solutions to assist persons with visual impairments (that is, those who are blind or have low vision) is frequently discussed and held to be widely beneficial in countless applications and daily activities. One such approach involving a tactile-vision sensory substitution modality as a mechanism to compensate for vision loss likewise holds such promise. It has been suggested that the use of a sensory substitution modality is an obvious and historically used mechanism of compensation for visual impairment and can be readily pointed to in a number of rudimentary, yet highly effective, strategies that are in use. Perhaps the most established and successful example of a sensory substitution strategy that targets persons who are visually impaired is the use of braille. Information that is typically acquired visually through reading is, instead, acquired through the fingertips and interpreted in the brain (Bach-y-Rita & Kercel, 2003). Another obvious sensory substitution approach that is commonly used to provide additional environmental information to travelers who are visually impaired is the use of a long cane (Bach-y-Rita & Kercel, 2003). Although a long cane has the potential to allow a variety of proprioceptive and kinesthetic information to be conveyed to a traveler (the material, slope, and elevation of the walking surface and the location and dimension of obstacles and openings along a path), it clearly meets the criteria of a sensory substitution strategy (Blasch, Wiener, & Welsh, 1997). A convincing argument can be made that adaptive strategies and techniques that are often taught to individuals with visual impairments involve a sensory substitution component. Previous efforts to develop a portable device to aid individuals who are visually impaired to acquire printed materials and images started with the Optacon (Optical-to-Tactile-Converter), originally manufactured by Telesensory Systems. As described in an owner's manual from 1978, the Optacon was "a portable reading aid for the blind that operates by use of a miniature camera, an electronics unit and a tactile simulator array that converts printed words and images into tactile images that a blind person can feel with one finger" (Optacon Owner's Manual, 1978). Although the Optacon is no longer manufactured or commercially available, a loyal base of users of this device continue to tout the advantages and utility of this platform for acquiring written information. The device examined in the study reported here is hardly novel from the point of view of being an augmentative tool to aid in the acquisition of environmental information, but does represent an intriguing and surprisingly intuitive interface for providing information to the user. The BrainPort vision device system--Wicab, BP-WAVE 2007--consists of a postage stampsized 25 x 25 electrotactile electrode array for the tongue (625 individual pinhead-sized points of contact arranged across the face of the array), a control box, a digital video camera, and a handheld controller for zoom and contrast inversion (see Figure 1). BrainPort technology converts images that are captured through a digital camera and presents this information to the brain via electrical stimulation of the tongue through the electrotactile electrode array, augmenting normal sensory channels with this additional spatial information (Arnoldussen & Hogle, 2008). Although this particular sensorysubstitution platform may at first appear unorthodox, numerous previous studies have supported the use of the tongue as a sensory channel for receiving input (Bach-y-Rita, 1967, 1972, 2005; Bach-y-Rita, Collins, Saunders, White, & Scadden, 1969; Bach-yRita, Kaczmarek, Tyler, & Garcia-Lara, 1998). Individuals who use this device have described the experience of the electrotactile electrode array as a feeling of effervescent bubbles mildly buzzing on the tongue. …