Extinction learning, which consists of the inhibition of retrieval, can be learned without retrieval

In the present study we test the hypothesis that extinction is not a consequence of retrieval in unreinforced conditioned stimulus (CS) presentation but the mere perception of the CS in the absence of a conditioned response. Animals with cannulae implanted in the CA1 region of hippocampus were subjected to extinction of contextual fear conditioning. Muscimol infused intra-CA1 before an extinction training session of contextual fear conditioning (CFC) blocks retrieval but not consolidation of extinction measured 24 h later. Additionally, this inhibition of retrieval does not affect early persistence of extinction when tested 7 d later or its spontaneous recovery after 2 wk. Furthermore, both anisomycin, an inhibitor of ribosomal protein synthesis, and rapamycin, an inhibitor of extraribosomal protein synthesis, given into the CA1, impair extinction of CFC regardless of whether its retrieval was blocked by muscimol. Therefore, retrieval performance in the first unreinforced session is not necessary for the installation, maintenance, or spontaneous recovery of extinction of CFC.

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Differential impairment of auditory and contextual fear conditioning by protein synthesis inhibition in C57BL/6N mice.

Behavioral Neuroscience ◽

10.1037/0735-7044.113.3.496 ◽

1999 ◽

Vol 113 (3) ◽

pp. 496-506 ◽

Cited By ~ 33

Author(s):

Oliver Stiedl ◽

Markki Palve ◽

Jelena Radulovic ◽

Karin Birkenfeld ◽

Joachim Spiess

Keyword(s):

Protein Synthesis ◽

Fear Conditioning ◽

Contextual Fear Conditioning ◽

Protein Synthesis Inhibition ◽

Contextual Fear ◽

Synthesis Inhibition

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Corticosterone differentially modulates time-dependent fear generalization following mild or moderate fear conditioning training in rats

10.1101/2021.03.10.434749 ◽

2021 ◽

Author(s):

Moisés dos Santos Corrêa ◽

Barbara dos Santos Vaz ◽

Beatriz Scazufca Menezes ◽

Tatiana Lima Ferreira ◽

Paula Ayako Tiba ◽

...

Keyword(s):

Fear Conditioning ◽

Training Session ◽

Contextual Fear Conditioning ◽

Time Dependent ◽

Control Group ◽

Stress System ◽

List Type ◽

Contextual Fear ◽

Male Wistar Rats ◽

Fear Generalization

ABSTRACTStressful and emotionally arousing experiences create strong memories that seem to lose specificity over time. It is uncertain, however, how the stress system contributes to the phenomenon of time-dependent fear generalization. Here, we investigated whether the glucocorticoid hormonal system affects the specificity of contextual fear memories at several timepoints. We trained male Wistar rats on the contextual fear conditioning (CFC) task using two footshock intensities (mild CFC, 3 footshocks of 0.3 mA, or moderate CFC, 3x 0.6 mA) and immediately after the training session we administered corticosterone (CORT-HBC) systemically. We first tested the animals in a novel context and then in the training context at different intervals following training (2, 14, 28 or 42 days). By measuring freezing in the novel context and then contrasting freezing times shown in both contexts, we inferred contextual fear generalization for each rat, classifying them into Generalizers or Discriminators. Following mild CFC training, the glucocorticoid induced an increased discriminative contextual memory that lasted from two up to 28 days. In contrast, after moderate CFC training, CORT-HBC facilitated contextual generalization at 14 days, compared to the control group that maintained contextual discrimination at this timepoint. For this training intensity, however, CORT-HBC did not have any effect on recent memory specificity. These findings indicate that manipulating glucocorticoid levels after mild or moderately arousing experiences may differentially modulate memory consolidation and time-dependent fear generalization.HIGHLIGHTS-Rats were trained in a contextual fear task and tested for fear generalization.-Corticosterone improved accuracy in mild fear conditioning (FC) up to 28 days.-Same treatment elicited time-dependent fear generalization in moderate FC training.

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