The effects of auditory thalamic lesions on the processing of an auditory safety signal for conditioned fear
M.A. (Master of Arts)
Department of Psychology
Fear; Emotional conditioning; Auditory evoked response; Thalamus--Wounds and injuries
Although much is known about the neural systems responsible for the acquisition and expression of conditioned fear, little is known about the neural systems responsible for the inhibition of fear. One procedure well suited for the investigation of inhibition of fear is the conditioned inhibition of fear-potentiated startle developed by Falls and Davis in 1995. The purpose of this study was to examine the effects of auditory thalamic lesions on the acquisition of conditioned inhibition to an auditory conditioned inhibitor. Rats were given either complete electrolytic auditory thalamic lesions or sham lesions prior to conditioned inhibition training. The training consisted of 15 light+shock pairings on each of 2 days followed by 5 light+shock trials intermixed with 15 noise—»light no shock trials on each of 5 days. This training procedure was designed to establish the noise as a conditioned inhibitor. Lesion, sham, and unoperated groups showed equivalent levels of conditioned inhibition of fear, defined as a reduction in fear-potentiated startle to the light when accompanied by the noise. These data suggest that the auditory thalamus is not critical for the acquisition of conditioned inhibition of fear-potentiated startle to an auditory conditioned inhibitor. Because lesions of the auditory thalamus have been shown to prevent the acquisition of fear-potentiated startle to an auditory CS, we evaluated whether our lesions would prevent acquisition of fear-potentiated startle to an auditory CS. The lesioned and a subset of sham animals were given 10 noise+shock pairings on each of 2 days. Lesioned animals showed significantly less fear-potentiated startle than sham animals, suggesting that the lesions were sufficient to prevent acquisition to an auditory CS. These results indicate that although the auditory thalamus may be important for the acquisition of fear to a noise CS, it is not critical for the acquisition of conditioned inhibition to a noise inhibitor.
Heldt, Scott A., "The effects of auditory thalamic lesions on the processing of an auditory safety signal for conditioned fear" (1998). Graduate Research Theses & Dissertations. 5614.
iv, 64 pages
Northern Illinois University
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Includes bibliographical references (pages -64)