Persons who are deaf or deaf-blind use the haptic senses to augment speech reading with vibrotactile aids, translate acoustic environmental events into palpable signals, or interpret finger-spelling. Similarly, persons who are blind use touch to read Braille or embossed maps, for mobility information, or to interpret vibrotactile displays of text. The long-term objective of this Program of Research is to understand better both the sensory and the perceptual processes that underlie rapid and accurate communication through the cutaneous senses. It is the specific aim of this application to explore spatial acuity in the context of vibrotactile pattern processing, along with the related ability to localize tactile stimulation. Although spatial acuity of the skin has been explored with pressure stimuli, there have been few attempts to study acuity for patterned vibratory stimuli of the type used in tactile devices for augmenting communication. Such systems include speech reading aids used by persons who are deaf (e.g. the Tactaid, placed on the forearm or abdomen), reading machines for persons who are blind (the Optacon, used on the fingertip), and spatial orientation systems used by pilots or astronauts (the TSAS, on the trunk). In every case, vibrotactile spatial acuity has never been empirically determined at the application site, so pattern perception potential might seem to be poorer than it is. In this proposal two projects will explore spatial acuity and localization ability for vibrotactile and pressure (for comparison) stimuli. First, baseline studies will measure localization with well-controlled stimuli on body sites used by wearable tactile communication aids and research devices. Because it is likely that stimulus parameters such as vibration frequency might affect localization, these will be varied. After the parameters for optimal absolute spatial localization have been determined, vibratory and pressure spatial acuity on each site will be explored by manipulating the spatial resolution of the arrays while measuring spatial pattern perception. Acuity at a site will be defined by the minimal tactor separations that produce criterion performance. Because tactile aids should be usable throughout a person's life span, but particularly in the later years, older persons will participate in this study of the spatial aspects of tactile pattern perception. The second project will examine the effects of prolonged stimulation on pattern perception: Many tactile communication systems are used for extended periods of time, and spatial distortions produced by adaptation can affect pattern perception.
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