Electrotactile stimulation relevant to sensory-motor rehabilitation: a progress report.

Several artificial sensory augmentation systems (ASAS) have been developed in recent years to compensate for loss of function in the visual, auditory, tactile, and kinesthetic senses . These ASA systems, which use either electrical or mechanical cutaneous stimulation as the display modality, have amplitude, frequency, and pulse width as the design concepts (Bach-y-Rita et al ., 1970: Saunders et al ., 1971 ; Kato et al ., 1970; Solomonow et al ., 1975; Bliss, 1967; and Prior et al ., 1976). A great deal of progress has been made through the various ASAS systems toward sensory recovery for the disabled ; however, limitation in both quantity and quality of information transmission has become evident, and more complex stimulation techniques need to be sought. In order to optimize various sensory aid systems, it was necessary to know more about the response of cutaneous receptors to stimulation codes. A search of the psycho-physiological literature indicated that most of the data that exist concern principally mechanical cutaneous stimulation (Bekesy, 1967; Weinstein, 1968; Eskildsen, 1969) . No data relating specifically to electrotactile two-point discrimination were found. It was necessary to devise experimental procedures to obtain data relating two-point discrimination thresholds (TPDT) to frequency, pulse width, pulse time delay, learning, body locus, and stimulation techniques . Some findings of these experiments are the subject of this paper.