Learned relationships between environmental stimuli (contexts) and reinforcers are important in a number of clinical syndromes. For instance, contextual fear conditioning in humans with panic disorder promotes avoidance of contextual stimuli (typically places) associated with panic attacks. Recent studies of contextual fear conditioning in rats have provided evidence that the hippocampal formation, a structure known to be important in human memory, is critical for this form of learning. For example, electrolytic lesions made in the dorsal hippocampus (DH) before contextual fear conditioning attenuate the subsequent acquisition of conditional freezing (a fear response in the rat characterized by immobility) to contextual stimuli paired with footshock. Similarly, electrolytic lesions of the entorhinal cortex (EC), the primary cortical afferent of the DH, produce deficits in the acquisition of conditional freezing. Given that the amygdala is essential for fear conditioning to both contextual and discrete stimuli, these data suggest that anatomical projections from the EC to the DH are part of a pathway by which contextual information reaches the amygdala for association with footshock. Although the involvement of the DH in contextual fear conditioning has been established, the route by which information processed in the DH reaches the amygdala is unknown. One possibility is that projections from the ventral subiculum (vSUB) to the amygdala constitute this pathway, however this hypothesis has yet to be tested. Therefore, the objective of the present project is to explore the impact of neurotoxic vSUB lesions on contextual fear conditioning in rats, and to examine the hypothesis that direct projections from the vSUB to the amygdala mediate the acquisition of contextual fear conditioning. The project will consist of three experiments. The first experiment will examine the acquisition and retention of contextual fear conditioning in rats with neurotoxic vSUB lesions; rats with neurotoxic EC or DH lesions will be included for comparison. The second experiment will anatomically disconnect the vSUB and amygdala to assess the contribution of this pathway to contextual fear conditioning. The third experiment will assess the impact of posttraining neurotoxic vSUB lesions on the expression of contextual fear. These experiments will provide important new information concerning the role of the vSUB and the vSUB-BLA projection in contextual fear conditioning in rats, and will provide further insight into the role of the hippocampal formation in learning and memory.