Abstract
The electrocutaneous communication by means of electric pulse stimuli has been studied. One of the most important problems in this kind of research is to determine the most relevant stimulus parameters for transmitting the information. These parameters are called informational dimensions of stimuli. In general, they consist of three factors: namely, frequency, space and magnitude. The frequency and the space dimensions are said to correspond to the pulse interval of stimuli and the number of electrodes, respectively. For the magnitude dimension, however, it had not been clarified which parameter is the most relevant.
In the previous paper we studied this problem and found the fact that the subjective magnitude of electrocutaneous stimuli is related to the pulse energy. This paper describes some problems about the constant energy electrocutaneous stimulation, namely, the design of energy measurement instrument, the measurement of energy threshold characteristics as a function of time, and estimation of the channel capacity from the measurement of a just noticeable difference.
The energy threshold, the current threshold and the pulse interval characteristics were measured as functions of time, using the constant energy stimulator designed by ourselves. It was found that the energy threshold remains constant with time, while the current threshold increases gradually with time. These results suggest that the magnitude sensation is more closely related to the pulse energy than the pulse current. Moreover, the channel capacity estimated from the measurement of a just noticeable difference was found to be 3.0 bits to 4.0 bits for five subjects.
