Electroencephaloǵraphic Changes Associated with Painful and Non-Painful Peripheral Stimulation

This work was undertaken to ascertain whcther the perception of pain is associated with a specific change in the electroencephalogram (E.E.G.), which might be used as an objective criterion of pain.

Methods. A Grass Electoencephalograph was used with 6 or 8 electrodes in 17 experiments on as many subjects. In addition to the usual 8 electrodes (2 frontals, 2 parietals, 2 temporals and 2 occipitals) the Grinker needte eIectlrodel in the sphenoid btone was employed tin 2 experiments, and a saline saturated cotton elelctrode prlessed against the posteritor pharyngeal wall in one. For the purpose of exploring any changes from the region of the base of the skull or hypothalamws near the foramm ovale in sbill another experiment an, insiullated needle electrode was inserted (under infiltration anesthesia) between thle mandible and zygoma to a depth of 5.5 cm. Monopolar registration was employed with the lobe of the ear as indifferent electrode. Pain was pnolduced in several ways in each experiment. (a) A Von Frey hair stimulator was applied to1 a previoudy determind pain point on the right forearm with a pressure of 8 g. (Ib) The webl of the skin between the thumb and index finger of the right hand was pressed between, a forceps. (c) As a control in two experiments heat, cold and touch were applied to the rigbt foreairm without causing pain.

Results. In all experiments a definite chang? in the E.E.G. occurred. It consisted of a decrease in amplitude, which was in the nature of a loss of electrical entropy and must be separatld flrom the attention wave, which frequently appeared as an addlitioaal factor. The change was not specific for a pain stimulus or sensation since a similar response was obtained with heat, cold and touch.