Effects of electrical hippocampal stimulation on acquisition and performance of unidirectional active avoidance response in cats.

The influence of electrical stimulation of the posterior part of the hippocampus on acquisition and performance of the conditioned, unidirectional avoidance response was investigated in 26 cats. No significant differences in the speed of learning between stimulated and control animals were observed. However, electrical hippocampal stimulation with parameters 7/s, 100 microamps, 7/s, 200 microamps and 50/s, 100 microamps (1 ms square pulses of negative polarity) facilitated the performance of the avoidance response. Strong hippocampal stimulation (50/s, 200 microamps) caused inhibitory effects. Application of hippocampal stimulation before experimental sessions increased the performance level in comparison to sessions not preceded by hippocampal stimulation.