The effect of post-training lateral hypothalamic self-stimulation on aversive and appetitive classical conditioning

The effect of post-training self-stimulation on associations formed during classical conditioning was studied. In Experiment 1, rats experienced pairings of a tone with shock and were allowed to self-stimulate either immediately, or after a delay of 2 hours. Rats in one control group did not self-stimulate after the tone-shock pairings; rats in a second control group self-stimulated after two unpaired tone and shock presentations. Twenty-four hours later, the ability of the tone to suppress drinking in the water-deprived rats was tested as a measure of retention. The rats in the paired, immediate self-stimulation group showed significantly more suppression than the rats in any other group. In Experiment 2, the tone was paired with licking a water tube. The rats self-stimulated either immediately after the pairings, or after a delay of two hours. Twenty-four hours later, the rats were tested in extinction (dry water tube/tone present). The rats in the immediate self-stimulation group showed significantly greater resistance to extinction than the rats in several self-stimulation and tone-absent control groups. These data suggest that self-stimulation can retroactively improve memory for associations formed in classical conditioning paradigms.