[Electrochemical activity at implanted metal electrodes as a response of the brain to injury]

The potentials of platinum electrodes implanted down to the dura mater (reference electrode - platinum, implanted into nasal bones), during 15-25 days after operation underwent a series of oscillation from +5 mV to -50 mV with a gradually extinguishing amplitude. It is assumed that these changes reflect metabolic reaction of the brain tissue to the implantation of electrodes and their presence at the brain surface. The greatest changes in electrode potential were observed in the experiments, in which the dura mater remained intact and the number of electrodes did not exceed 25. Animals with 100-150 electrodes died several days following operation. It is also assumed that even relatively "harmless" platinum electrodes, besides their purely mechanical influence, disrupt normal course of biochemical processes in the brain. Potential of the silver plates, unlike that of platinum electrodes, did not decrease with time but was enhanced. These changes seem to be due both to the damaging effect of silver on brain and to the oxidation of electrodes which gives reason to consider silver unfit for leading off of potentials in chronic experiments.