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Learn Mem. 2016 Jun 17;23(7):379-85. doi: 10.1101/lm.041400.115. Print 2016 Jul.

Conditioning- and time-dependent increases in context fear and generalization.

Author information

1
Department of Psychology and Center for Neuroscience, University at Albany, State University of New York, Albany, New York 12222, USA Department of Psychology, University of California, Los Angeles, Los Angeles, California 90095, USA apoulos@albany.edu.
2
Department of Psychology, University of California, Los Angeles, Los Angeles, California 90095, USA.
3
Department of Psychology and Center for Neuroscience, University at Albany, State University of New York, Albany, New York 12222, USA.
4
Department of Psychology, University of California, Los Angeles, Los Angeles, California 90095, USA Department of Psychiatry, University of California, Los Angeles, Los Angeles, California 90095, USA.

Abstract

A prominent feature of fear memories and anxiety disorders is that they endure across extended periods of time. Here, we examine how the severity of the initial fear experience influences incubation, generalization, and sensitization of contextual fear memories across time. Adult rats were presented with either five, two, one, or zero shocks (1.2 mA, 2 sec) during contextual fear conditioning. Following a recent (1 d) or remote (28 d) retention interval all subjects were returned to the original training context to measure fear memory and/or to a novel context to measure the specificity of fear conditioning. Our results indicate rats that received two or five shocks show an "incubation"-like enhancement of fear between recent and remote retention intervals, while single-shocked animals show stable levels of context fear memory. Moreover, when fear was tested in a novel context, 1 and 2 shocked groups failed to freeze, whereas five shocked rats showed a time-dependent generalization of context memory. Stress enhancement of fear learning to a second round of conditioning was evident in all previously shocked animals. Based on these results, we conclude that the severity or number of foot shocks determines not only the level of fear memory, but also the time-dependent incubation of fear and its generalization across distinct contexts.

PMID:
27317198
PMCID:
PMC4918784
DOI:
10.1101/lm.041400.115
[Indexed for MEDLINE]
Free PMC Article

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