Electrocutaneous stimulation: Psychometric functions and temporal integration

Psychometric functions and psychophysical strength-duration curves were obtained with rectangular electro-cutaneous pulses. The slopes of the psychometric functions were much steeper than corresponding functions in other modalities, with the standard deviation of the distribution only about 0.08 times the threshold. Precise monitoring of stimulus current showed that physiological rather than physical variability was involved. Psychophysical strength-duration curves support the contention that large A-fibers are directly stimulated. Data from this study. as well as from comparable I × t experiments in other senses, are well-fit throughout the range of durations by rectangular hyperbolas. The period over which complete temporal summation occurs is only about 0.5 msec.