Shock-induced enhancement of learning

Abstract

Moderate tailshock (3, 0.75 s, 1 mA) has been found to enhance subsequent Pavlovian fear conditioning to footshock in a different context. The current experiments examine whether this effect generalizes to other Pavlovian phenomena. Experiment 1 found that moderate tailshock enhances startle in an unconditioned manner. In addition, it enhanced fear conditioning to the context that had been paired with the startle-eliciting stimulus. Experiment 2 revealed that learning about an appetitive US in a morphine conditioned place preference paradigm is also facilitated. Interestingly, moderate tailshock induced a negative affective state that was sufficient to induce a conditioned aversion. Experiment 3 replicated the original finding that moderate tailshock enhances fear conditioning using weak gridshock as the US. Surprisingly, rats that were trained prior to tube restraint exhibited elevated levels of conditioning. Presenting tailshock after the conditioning episode had no effect on the level of freezing observed 24 h later. These findings suggest that moderate tailshock produces a general sensitization that applies to a variety of stimuli. Moreover, other arousing events can produce a similar enhancement in Pavlovian Conditioning.