The project will develop two high resolution tactual displays (also called dense arrays). Each device will contain 400 elements, arranged in a 20 by 20 array. The frequency, 0 to 400 Hz, and amplitudes, up to 3.0 mm peak-to-peak, of the mechanical vibration of each element in the array will be individually controlled. The center-to-center spacing of the stimulator tips in contact with the skin will be 0.4 mm when contacting the most sensitive skin surfaces. For less sensitive areas the spacing will be increased. The frequency, amplitude, and spatial separation of the stimulator tips permit the dense array to match or exceed the sensory capabilities of the skin. Initially the dense stimulators will be used to investigate tactual spatial pattern processing. Psychophysical studies with human subjects will be conducted in conjunction with neurophysiological studies with nonhuman primates. Neurophysiological recordings will be made of first-order afferents as well as cells in primary somatosensory cortex. By appropriate selection of frequency and amplitude of stimulation, spatial patterns will be generated that stimulate one or another of the primary afferent systems selectively. Spatial sensitivity of and interactions between the afferent systems will be examined both psychophysically and neurophysiologically. The dense array will be used to evaluate how prolonged exposure to distorted Spatial patterns affects the spatial organization of limited areas of skin. The arrays will be used to simulate realistic tactual stimuli and to evaluate current theories of the perception of roughness and slip. The arrays will also be used to examine biomechanical responses of the skin.
