Early extinction after fear conditioning yields a context-independent and short-term suppression of conditional freezing in rats - PubMed (original) (raw)

Early extinction after fear conditioning yields a context-independent and short-term suppression of conditional freezing in rats

Chun-hui Chang et al. Learn Mem. 2009.

Abstract

Extinction of Pavlovian fear conditioning in rats is a useful model for therapeutic interventions in humans with anxiety disorders. Recently, we found that delivering extinction trials soon (15 min) after fear conditioning yields a short-term suppression of fear, but little long-term extinction. Here, we explored the possible mechanisms underlying this deficit by assessing the suppression of fear to a CS immediately after extinction training (Experiment 1) and the context specificity of fear after both immediate and delayed extinction training (Experiment 2). We also examined the time course of the immediate extinction deficit (Experiment 3). Our results indicate that immediate extinction produces a short-lived and context-independent suppression of conditional freezing. Deficits in long-term extinction were apparent even when the extinction trials were given up to 6 h after conditioning. Moreover, this deficit was not due to different retention intervals that might have influenced the degree of spontaneous recovery after immediate and delayed extinction (Experiment 4). These results suggest that fear suppression under immediate extinction may be due to a short-term, context-independent habituation process, rather than extinction per se. Long-term extinction memory only develops when extinction training occurs at least six hours after conditioning.

PubMed Disclaimer

Figures

Figure 1.

Figure 1.

Probe CS after immediate extinction. (A) Percentage of freezing behavior during conditioning. Data are 1-min averages for the periods before (baseline, BL) and after each of five tone-shock conditioning trials. (B) Percentage of freezing behavior during the extinction session, which occurred 15 min after conditioning. Control rats did not receive CS presentations during extinction (NO-EXT). (C) Percentage of freezing behavior during the probe CS 15 min after extinction. Baseline freezing data were averaged and subtracted from the freezing level during probe CS to yield normalized freezing. (D) Normalized average percentage of freezing across test trials during retention test 48 h after conditioning. All data are means ± SEM.

Figure 2.

Figure 2.

Renewal of fear response immediately after immediate or delayed extinction. Shown are averaged two-trial block percentages of freezing levels during early extinction, late extinction, and early renewal in immediate (A) and delayed (B) extinction conditions. All data are means ± SEM.

Figure 3.

Figure 3.

Percentage of freezing levels during retention test after different delays between conditioning and extinction sessions. All data are means ± SEM.

Figure 4.

Figure 4.

Percentage of freezing levels during retention test with equated extinction–retention test intervals. All data are mean ± SEM. *P < 0.05.

Similar articles

Cited by

References

    1. Bisson J.I., Jenkins P.L., Alexander J., Bannister C. Randomised controlled trial of psychological debriefing for victims of acute burn trauma. Br. J. Psychiatry. 1997;171:78–81. - PubMed
    1. Bouton M.E. Context, ambiguity, and unlearning: Sources of relapse after behavioral extinction. Biol. Psychiatry. 2002;52:976–986. - PubMed
    1. Bouton M.E. Context and behavioral processes in extinction. Learn. Mem. 2004;11:485–494. - PubMed
    1. Bouton M.E., Garcia-Gutierrez A. Intertrial interval as a contextual stimulus. Behav. Processes. 2006;71:307–317. - PubMed
    1. Bouton M.E., Mineka S., Barlow D.H. A modern learning theory perspective on the etiology of panic disorder. Psychol. Rev. 2001;108:4–32. - PubMed

Publication types

MeSH terms

LinkOut - more resources