Effects of Pulse Height and Pulse Width on the Magnitude Sensation of Electrocutaneous Stimulus

Abstract

The subjective magnitude of sensation for electrocutaneous stimuli is experimentally studied.
In experiment I, two pulse trains, which have the same pulse interval and stimulus duration but have the different pulse heights (I_A & I_B) and pulse widths (T_A & T_B), have been applied to the skin just above the triceps of a subject via wet electrodes. And tests were made using AB method how various stimulus pairs give the different magnitude sensation or how they give the same magnitude sensation under the various conditions of I_B and T_B for several values of pulse interval as a parameter, while I_A and T_A were fixed to 4.7 mA and 100 μs respectively, as a reference.
In experiment II, the threshold current of minimum sensation for various pulse width has been examined also by using AB method.
The most important findings :
1) For the pulse trains of 100 ms and 50 ms pulse interval, stimulus A with pulse height I_A and pulse width T_A and stimulus B with I_B and T_B give the same magnitude sensation if they meet the following condition :
I_A²T_A = I_B²T_B (even if T_A≠ T_B)
threshold current< I_A, I_B<<threshold of pain
0< T_A, T_B<1000 μs
2) For the stimuli of pulse interval of 20 ms and 10 ms, the same tendencies have been found, but the difference is slightly detected even if they meet the condition of 1).
3) The threshold of minimum sensation is obtained when the current I reaches the value which holds the condition I²T= constant for various Ts, if T<1 000μs.
These facts suggest that the electrocutaneous magnitude sensation is strongly affected by theenergy of one pulse if the pulse width is less than 1 ms, more correctly, by the integrated value_ of instantaneous power (ZI²) for about 1 ms.