Thesis (M.A.)--Baylor University, 2009. / Includes bibliographical references (p. 44-55).

No description available.

No description available.

No description available.

Switching between a state of fear and safety is a critical aspect of adaptive behavior. Aversive and non-aversive associations must be formed quickly and reliably but remain malleable as these associations change dynamically. When these associations become biased towards aversive associations by traumatic and stressful circumstances, as in PTSD, fear generalization and impaired fear extinction arise. These changes are associated with reduced activity in the medial prefrontal cortex (mPFC) and enhanced activity in the basolateral amygdala (BLA). It has been hypothesized that the mPFC mediates top-down control of the BLA to signal safety. It has previously been demonstrated that synchronous activity within the mPFC-BLA circuit is strongly engaged during fear conditioning, but it is unknown how activity in this circuit changes to mediate aversive discrimination. We investigated how the mPFC and BLA cooperate to mediate successful discrimination between aversive and non-aversive stimuli both for learned and innately-valent associations. Extracellular elecrophysiological recordings were obtained simultaneously form the mPFC and BLA in mice during innate anxiety, fear discrimination, and fear extinction. Local field potentials were recorded in both structures along with single unit recordings from the BLA. We discovered that fear was associated with enhanced theta-frequency synchrony and theta-gamma coupling within the mPFC-BLA circuit. On the other hand, safety was associated with predominant mPFC-to-BLA directionality of synchronous information flow and enhanced fast gamma frequency activity in both structures. Interestingly, gamma oscillations in the BLA were strongly coupled to theta frequency activity arising in the mPFC. This data is consistent with entrainment of inhibitory circuits in the BLA by mPFC input to mediate safety.

This series of experiments used the multiple learning and memory systems hypothesis of the mammalian nervous system to investigate the possibility that the amygdala, dorsal striatum, and hippocampal systems might, in certain situations, interact to produce behavior in the normal animal. Using variations of the conditioned-cue preference (CCP) task, evidence is presented showing that context-specific information acquired by the hippocampus interferes with acquisition of amygdala-based stimulus-reward learning. It was also demonstrated that there are amygdala-, dorsal striatum-, and hippocampus-based forms of place learning and that cue ambiguity and movement are important factors determining which of these learning and memory systems gain behavioral control in place learning situations. These findings provide evidence for interactions among learning and memory systems and implicate the amygdala and dorsal striatum in some types of non-hippocampal based place learning using distal cues.

Thesis (M. Sc.)--Carleton University, 2002. / Includes bibliographical references (p. 159-161). Also available in electronic format on the Internet.

Thesis (M. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 40-50). Also available in electronic format on the Internet.

Thesis (M. Sc.)--Carleton University, 2008. / Includes bibliographical references (p. 71-81). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of California, San Diego, and San Diego State University, 2005. / Vita. Includes bibliographical references (leaves 160-178).