Contextual fear conditioning was tested in infant, adolescent, and adult rats in terms of Pavlovian conditioned suppression. When a discrete auditory conditioned stimulus (CS) was paired with footshock (unconditioned stimulus, US) within the largely olfactory context, infants and adolescents conditioned to the context with substantial effectiveness but adult rats did not. When unpaired presentations of the CS and US occurred within the context, contextual fear conditioning was strong for adults, weak for infants, but about as strong for adolescents as when pairings of CS and US occurred in the context. Nonreinforced presentations of either the CS or context markedly reduced contextual fear conditioning in infants, but, in adolescents, CS extinction had no effect on contextual fear conditioning, although context extinction significantly reduced it. Neither CS extinction nor context extinction affected responding to the CS-context compound in infants, suggesting striking discrimination between the compound and its components. Female adolescents showed the same lack of effect of component extinction on response to the compound as infants, but CS extinction reduced responding to the compound in adolescent males, a sex difference seen also in adults. Theoretical implications are discussed for the development of perceptual-cognitive processing and hippocampus role. Keywordscontextual fear conditioning; fear extinction; learning; olfactory context; hippocampus; ontogeny Contextual fear conditioning has received a lot of attention from behavioral neuroscientists during the last decade (e.g., Anagnostaras, Gale, & Fanselow, 2001;Fanselow & Poulos, 2004;Phillips & LeDoux, 1992). The purpose of this report is to assess the effectiveness of contextual fear conditioning experiments by rats at each of three disparate periods of ontogeny: late infancy, adolescence and early adulthood. The ontogeny of contextual fear conditioning is of interest because --in relation to conditioning of other events within the context--it can Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. provide a window to the ontogeny of encoding and memory organization (e.g., Brasser & Spear, 2004;Lariviere, Chen, & Spear, 1990), and because it has been used as a marker for the development of brain function important for memory (e.g., Pugh & Rudy, 1996;Rudy & Morledge, 1994). NIH Public AccessSeveral experiments led to the conclusion that acquisition of an aversion to a particular context paired with footshock is less effective in rats during late infancy (postnatal days 17-20, P17-20) than in weaned juvenile ...

Stimulus competition (e.g., blocking) has been observed between antecedent events (i.e., conditioned stimuli or potential causes), but recent evidence within the human causal learning literature suggests that it could also be obtained between subsequent events (i.e., unconditioned stimuli or potential effects). The present research tested this hypothesis with rat subjects. To avoid confounding the antecedent versus subsequent variable with the affective value of the events involved (i.e., unconditioned stimuli are ordinarily of greater affective value than conditioned stimuli), a preparation was used in which antecedent and subsequent events all lacked affective value during the blocking phases of the study. This was achieved through the use of sensory preconditioning. Blocking of subsequent events as well as antecedent events was observed. The challenge to most associative theories that is provided by Mocking of subsequent events is discussed.

To test several predictions derived from a behavior-systems approach, the authors assessed Pavlovian fear conditioning in rats after 30 trials of forward, simultaneous, or unpaired training. Direct evidence of conditioned fear was collected through observation of flight and freezing reactions during presentations of the conditioned stimulus (CS) alone. The authors also tested the CS's potential to reinforce an instrumental escape response in an escape-from-fear paradigm. On the one hand, rats that received forward training showed conditioned freezing, but no conditioned flight was observed. On the other hand, rats that received simultaneous training showed conditioned flight, but no conditioned freezing was observed. Rats that received either forward or simultaneous pairings showed instrumental learning of the escape-from-fear response. Implications for several theories of Pavlovian conditioning are discussed.

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