Context pre-exposure obscures amygdala modulation of contextual-fear conditioning.

We report that post-training inactivation of basolateral amygdala region (BLA) with muscimol impaired memory for contextual-fear conditioning (as measured by freezing) and intra-BLA norepinephrine enhanced this memory. However, pre-exposure to the context eliminated both of these effects. These findings provide a likely explanation of why an earler study failed to observe that the BLA modulates contextual fear conditioning-they pre-exposed their rats to the context. These results also suggest that the amygdala modulates the storage of the context fear memory and may do so by influencing the storage of the representation of the context in which the shock occurred.