Abstract
A lack of knowledge of the exact treatment current has hindered the standardization of electrical shock therapy. This has been especially true because the treatment current does not appear to follow “Ohm's law”—that is, the current is not equal to the treatment voltage divided by the measured (d-c) resistance between the electrodes, but usually is considerably higher. Also, the resistance varies in what has appeared to be an “unpredictable” manner. For these reasons, an a priori selection of the treatment current has appeared to be impossible.
It is, of course, the passage of the electric current which is responsible for the convulsive shocks, rather than the applied voltage of itself, so that dosage standardization must be on the basis of the former. The voltage required to obtain a given current will depend upon many factors, such as the thickness of the skull, area of electrodes, condition of the skin, etc. Obviously a rational prescription of dosage requires some method of taking these factors into account. This was recognized even in the original work of Cerletti and Bini (1938), who employed a d-c resistance measurement as mentioned above. However, this bears no relationship to the effective resistance during treatment.
A study of the electrical properties of the tissues involved offers an explanation of the apparently anomalous behavior of the resistance. This has made possible the accurate preselection of the treatment current used in shock therapy.
Method. Two electrodes were placed on the subject's head, using electrode jelly, as for shock treatment. The alternating current impedance between these was measured at frequencies of from 50 to 15,000 c.p.s. by means of an impedance bridge.∗. The very low current employed produced no stimulation. The alternating current impedance of tissue may be separated into two components: the resistance or energy dissipating portion; and the reactive, or energy storing portion.
Get full access to this article
View all access options for this article.