A general-purpose electrotactile (electrocutaneous) stimulation system has been developed as a research tool for studying psychophysiological performance associated with various stimulation waveforms. An experimenter-defined command file specifies the stimulation current and waveform of each of the 16 channels. The system provides a burst onset delay of 0-20 ms, a phase current of 0-50 mA, an interphase interval of 0-1000 mu s, 1-100 pulses per burst, a pulse repetition rate of 0.1-25 kHz, a phase width of 2-1000 mu s, and functionally monophasic pulses (with zero DC current) or balanced-biphasic pulses (with equal positive and negative phases). The system automatically delivers the desired stimulation, prompts the subject for responses, and then logs subject responses. Key features of the system are (1) the very flexible choice of bursts of pulsatile waveforms, (2) the real-time control of all of the waveform parameters as mathematical functions of external analog inputs, and (3) the high-performance electrode-driver circuitry.
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