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Krasnow Institute > Monday Seminars > Abstracts
EVOLUTION OF ACOUSTIC STARTLE PATHWAYS BELIEVED TO BE DISTURBED IN POSTTRAUMATIC STRESS DISORDER Kelly Cookson One of the defining symptoms of posttraumatic stress disorder is exaggerated startle responses. Acoustic startle responses in people diagnosed with posttraumatic stress disorder show elevated baseline magnitudes, increased fear-potentiation magnitudes, and impaired prepulse inhibition. Mammalian animal models have recently been proposed to investigate the basic neural mechanisms involved in modulating acoustic startle responses. Two strategies for extending the use of these models is to examine comparable neural mechanisms in nonmammalian species and to examine typically neglected startle responses, such as vocalizations. The present investigation examined neural pathways in a species of parrot, the budgerigar, comparable to the neural pathways that modulate acoustic startle responses in mammals. Pathway tracing studies indicate that budgerigars possess a complex set of neural pathways comparable to those that potentiate and inhibit acoustic startle responses in mammals. Some of the nuclei in these pathways are connected to vocal control nuclei and may play a role in mediating fear-related vocalizations. Immunohistochemical observations further show that these neural pathways utilize neuro- transmitters similar to those utilized in mammals. These findings suggest that the basic neural mechanisms involved in modulating acoustic startle responses are evolutionarily ancient. Comparisons of these mechanisms in birds and mammals may contribute to a better understanding of the basic neural mechanisms believed to be disturbed in posttraumatic stress disorder.
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