Effects of external cathodal polarization on classical motor conditioning in dogs

The present study was designed to determine the effects of cathodal polarization on the establishment of motor conditional reflexes (CR's), with faradic shock as reinforcement. Ten dogs were used as controls and another seven as experimental subjects (ES's). In the ES's, stainless-steel electrodes were implanted on the face, infraorbitally, for chronic polarization. Four days later the ES's were trained in a soundproof room with classical conditioning procedures while they were co9nstantly polarized with direct current (1 to 2 ma). Control dogs showed strong (+3 and +4) motor CR's within the first 50reinforced trials, with differentiation after 50 trials. In contrast, the ES's showed poor motor conditioning: six ES's showed poor motor CR's in the first 50 reinforced trials. Only one ES showed prompt, good motor CR's. The fact that cathodal polarization interferes with the establishment of motor CR's suggests an inhibitory effect on the acquisition of musculoskeletal CR's. It is possible that the inhibitory effects observed are related to the depression produced by cathodal polarization in humans.