Discriminative and nondiscriminative contextual fear conditioning potentiate the acoustic startle response

The acoustic startle reflex, a short-latency motor response to a loud noise, is modifiable by experience. Here we test whether contextual fear conditioning potentiates startle responses, in addition to two other indices of fear: freezing and defecation. First, we trained rats with zero, one or three 0.6-mA footshocks. Upon reexposure to the same context, startle responses, amount of time freezing, and defecation were increased in the one- and three-shock groups, but not in the zero-shock group, compared with pretraining baseline levels. Second, to test whether these increases in fear responses were context specific, we trained and tested rats in a context discrimination paradigm. Rats were trained to discriminate between two contexts, one in which three footshocks where delivered, the other in which no footshocks were delivered. Startle amplitudes and time spent freezing were increased in the paired as opposed to the unpaired context. These results suggest that the acoustic startle reflex can be modified by a specific memory of an environmental context in which an aversive event has occurred.