Influence of stimulus preexposure and of context familiarity on conditioned freezing behavior

1. This paper reports an experiment examining the influence of context on latent inhibition using conditioned freezing behavior as an index. 2. Two groups of 8 Wistar rats (290-320 g) were placed in one chamber (Context 2) and either exposed 7 times or not to a sound stimulus (68 dB, 90 s). Two additional groups of 8 rats received the same stimulation in a different environment (Context 1). Next, each rat was required to form a sound-shock (0.2 mA, 1.5 s) association (20 trials) in Context 2. Freezing behavior was measured both during sound (CS) presentation and during an equal period of time immediately preceding the CS. 3. When the test environment was familiar, the conditioning of fear was greater in the non-preexposed than in the CS-preexposed group. Acquisition of conditioned freezing was intermediate when the test environment was unfamiliar, irrespective of CS preexposure. 4. These results further support the context specificity of latent inhibition. In addition, they suggest that novelty interferes with sound-shock associations.