The ecology and ontogeny of odor fear learning
Item
-
Title
-
The ecology and ontogeny of odor fear learning
-
Identifier
-
d_2009_2013:bf9a63ca8153:10611
-
identifier
-
10848
-
Creator
-
Kabitzke, Patricia A.,
-
Contributor
-
Christoph Wiedenmayer | Michael Lewis
-
Date
-
2010
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Psychobiology | Developmental psychology | Behavioral psychology | CREB | development | fear conditioning | norepinephrine | predator odor | rodents
-
Abstract
-
Predator odors have been found to induce unconditioned fear in adult animals and provide the opportunity to study the mechanisms underlying unlearned and learned fear. The clinical application of this research is to explore the causal relationships between aversive events and psychopathologies such as PTSD. However, trauma often occurs early in life but most current investigations use adult animals in paradigms that employ stimuli with little ecological relevance in limited environmental contexts. Additionally, predator threats change across an animal's lifetime, as do abilities that enable the animal to learn or engage in different defensive behaviors. Thus, the first objective of this study was to determine the combination of factors that successfully induce unlearned fear to predator odor across development. Cat odor effectively induced fear-related behavior across development using the behavioral measure of freezing, especially in infant (PN14) and juvenile (PN26) rats. Once these parameters were understood, they were exploited to develop a learning paradigm to predator odors that could be used in early life. Cat odor produced unlearned, innate fear in infant and juvenile rats, but contextual fear learning occurred only in juveniles. The mechanisms underlying the development of this learning in early life were then explored. It was hypothesized that contextual fear learning is mediated by norepinephrine. Systemic injections of the beta-adrenergic antagonist propranolol before exposure to the cat odor reduced the unlearned fear response and memory acquisition whereas injection of propranolol after exposure to cat odor inhibited contextual fear learning in juvenile rats. We suggest that NE mediates the formation of contextual fear memories by activation of the transcription factor CREB in the hippocampus in juveniles but not in infants. Levels of phosphorylated CREB (pCREB) were increased in the dorsal and ventral hippocampus in juvenile, but not infant, rats that had been exposed to cat odor but not in animals exposed to a control odor. Further, propranolol blocked these increases in pCREB. Taken together, these results indicate that, although innate fear occurs within the neonatal period, contextual fear learning is a relatively late-occurring event, is hippocampal dependent, and mediated by norepinephrine.
-
Type
-
dissertation
-
Source
-
2009_2013.csv
-
degree
-
Ph.D.
-
Program
-
Psychology
