Electrolytic post-training lesions of the bed nucleus of the stria terminalis block startle potentiation in a cued fear conditioning procedure
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Existing neuroanatomical models argue that the bed nucleus of the stria terminalis (BST) principally mediates sustained, long-lasting fear or anxiety responses, but not shorter, phasic fear responses, although recent studies paint a more complex picture. In the current study, we evaluated the effect of post-training electrolytic BST lesions in a cued fear conditioning protocol with relatively short (10 s) tones. We hypothesized that the BST would not play a crucial role in the expression of fear upon re-exposure to the conditioned tones. Tone fear memory was primarily assessed through fear-potentiated startle. In addition, freezing measurements were obtained throughout the test sessions. In a series of three experiments, we explored the effects of BST lesions, taking into consideration contextual influences on cued fear expression (using (dis)similar training and test contexts) and temporal involvement of the BST in the consolidation of fear learning (lesion induction 3 or 27 h after fear conditioning). In all three experiments, we found that post-training electrolytic lesions of the BST significantly reduced fear-potentiated startle, implying a deficit in differentiation between tone and context. These results are surprising and challenge the general consensus on the lack of BST involvement in cued fear. We discuss several alternative explanations that may account for these unexpected findings.
KeywordsBed nucleus of the stria terminalis Fear Conditioning Auditory fear conditioning Rat Startle Freezing Electrolytic lesions
We acknowledge the financial support of the Medtronic Chair for Stereotactic Neurosurgery in Psychiatric Disorders, of which Bart Nuttin is chair holder, the Research Foundation—Flanders (FWO) [Research Projects G072909N and G0C9817N, and Postdoctoral Fellowship 1295613N (to Laura Luyten)], the European Research Council (CoG 64817), as well as the KU Leuven Center for Excellence on Generalization Research Grant PF/10/005. We would like to thank Marjolijn Deprez, Steve Ravelingien, Kelly Pelsmaekers, Ineke Pillet and Anna-Elisabeth Schnell for their contributions to the behavioral and histological analyses. We also thank Prof. Tom Beckers for the helpful discussions during the preparation of this manuscript.
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