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In three experiments using the barpress conditioned suppression task with albino rats, we studied the renewal (relapse) of conditioned fear in an ABA fear-renewal paradigm. We found that explicitly unpaired (EU) deliveries of conditioned stimuli (CSs) and unconditioned stimuli (USs) in Context B thwarted fear renewal in Context A. Evidence contraindicated a suggestion by Rauhut, Thomas, and Ayres (2001) that US habituation plays a key role in this effect. For example, renewal was thwarted only when EU CSs and USs were intermingled rather than given in succession. The possibility that EU treatments thwart renewal by creating a CS that inhibits fear in the test context also received no support. Thus, summation and retardation tests in Context A found no evidence that the EU CS became inhibitory, finding instead evidence for a residual excitation. Other possible interpretations of the results and some implications for clinical practice are noted.

In four experiments using albino rats in an ABA fear renewal paradigm, we studied conditioned fear in the A test context following extinction in Context B. Conditioned suppression of operant responding was the index of fear. In Experiments 1-3, we found that extinguishing a feared cue in compound with a putative conditioned inhibitor of fear led to more fear in the test context than did a conventional extinction procedure. In Experiments 4a and 4b, we found that extinguishing three feared cues in compound required one third the time and generally led to less fear to the cues in the test context than did the extinction of each cue separately. Thus, fear in the test context seems to vary inversely with the values of co-present cues during extinction in Context B. Results imply that cue value is actually reduced by extinction procedures rather than merely being opposed by a growing inhibitory process. Implications for theories of renewal and for clinical practice are discussed.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.lmot.2004.11.005 Byline: Brian L. Thomas (a), Craig L. Longo (b), John J.B. Ayres (b) Keywords: Fear; Renewal; Relapse; Phobias; Extinction; US habituation; Retrospective revaluation; Conditioned suppression; Animal models Abstract: In three experiments using the barpress conditioned suppression task with albino rats, we studied the renewal (relapse) of conditioned fear in an ABA fear-renewal paradigm. We found that explicitly unpaired (EU) deliveries of conditioned stimuli (CSs) and unconditioned stimuli (USs) in Context B thwarted fear renewal in Context A. Evidence contraindicated a suggestion by that US habituation plays a key role in this effect. For example, renewal was thwarted only when EU CSs and USs were intermingled rather than given in succession. The possibility that EU treatments thwart renewal by creating a CS that inhibits fear in the test context also received no support. Thus, summation and retardation tests in Context A found no evidence that the EU CS became inhibitory, finding instead evidence for a residual excitation. Other possible interpretations of the results and some implications for clinical practice are noted. Author Affiliation: (a) Department of Psychology, Baldwin-Wallace College, 275 Eastland Road, Berea, OH 44017-2088, USA (b) Department of Psychology, University of Massachusetts, Tobin Hall, Amherst, MA 01003, USA Article History: Received 21 July 2004; Revised 16 November 2004 Article Note: (footnote) [star] Support for this work came from National Institute of Mental Health Grant MH57459 awarded to the University of Massachusetts. Any opinions, findings, and conclusions or recommendations expressed are those of the authors and do not necessarily reflect the views of the granting agency. We thank Joseph A. Mooney, III for introducing us to DeoxIT D5. We thank Aaron Froelich, Katie Shai, and Drina Vurbic for their assistance with the second replication of Experiment 4.

This article discusses an experiment conducted on rats using retention-interval and context-switch maneuvers with the intent to affect retrieval of interfering associations. The authors conclude that learning-deficit theory produced better results over a retrieval-interference version of performance-deficit theory.

In a sample of 208 Holtzman-descended albino rats, we found evidence with 4 measures of conditioning (freezing, defecation, side crossing, and nose crossing) that a single 2-s, 1.0-mA immediate shock could condition fear to a context (Experiments 1, 2, and 4). When we reduced the shock intensity to 0.5 mA, we obtained a complete immediate-shock conditioning deficit according to all measures in Experiment 3 and to all but the defecation measure in Experiment 4. Results suggest two conclusions: (a) Differences in shock potency between laboratories may help explain discrepant findings about whether immediate shock supports contextual conditioning; (b) theories of contextual conditioning need a mechanism that permits that conditioning to result from immediate shock.

Four experiments using barpress conditioned suppression in rats found that tone evoked more freezing (immobility) than did light. Still, tone and light appeared to have similar conditioned value as assessed by suppression in Experiments 1, 2, and 3, and by blocking, second-order conditioning, and overconditioning assays in Experiments 1, 2, and 3, respectively. Experiment 4 arranged for tone to evoke less suppression than light but more freezing. Results suggest that in fear conditioning, the nature of the conditioned stimulus affects the form of conditioned responding (strong vs. weak freezing). This conclusion extends one drawn by P. C. Holland (1977) on the basis of his work in appetitive conditioning.

Conditioned suppression was used with rats to study the effects of extending conditioned stimuli (CSs) before versus after the delivery of unconditioned stimuli. These extensions are termed B and A extensions, respectively. Within-group designs were used to compare the effects of extending CSs when 2-min parts of those CSs were separated by temporal gaps of 6 min versus a separation of no gap. The results were as follows: (a) B extensions weakened conditioning more than did A extensions, with or without gaps; (b) under some conditions, this asymmetrical effect persisted with extended training; (c) gaps between 2-min parts of a B extension had no detectable effect; and (d) under some parameter values, gaps between 2-min parts of an A extension weakened conditioning significantly. These results are better predicted by the Sometimes Opponent-Process model (SOP; A. R. Wagner, 1981) than by the Rescorla-Wagner-Frey-Sears real-time model.

One path to human phobia may be one-trial backward fear conditioning. Human phobias transfer readily across contexts. However, animal studies of one-trial backward fear conditioning have yet to demonstrate such transfer. The present study sought to do so. It used a lick-suppression procedure with 84 naive male albino rats. Two conditioning contexts, designated O and V, were crossed factorially with two test contexts, O and V. Within each cell of the factorial design, rats received in the conditioning context either a single 12 sec tone backward paired with a single 4 sec 1 mA shock or the same tone explicitly unpaired with shock. Fear of context and fear of tone were subsequently assessed in term of the suppression of licking that they evoked. Test results suggested that (1) the rats discriminated between contexts O and V, and (2) despite such discrimination, one-trial backward fear conditioning transfered across the two contexts. The results enhance the plausibility of one-trial backward fear conditioning as a source of human phobia.

The influence of different parameters associated with latent inhibition was examined in three experiments with rats using the conditioned suppression procedure. Total preexposure time of the conditioned stimulus was found to be the most important factor. Similarity of duration of the preexposure and training times had some effect, whereas the number of preexposure trials was found to be unimportant when total time was constant.

Two experiments using conditioned suppression in rats tested the computer-simulated predictions of two real-time models of Pavlovian conditioning. The predictions concerned the effects of extending conditioned stimuli (CSs) before vs after the delivery of unconditioned stimuli (USs). In Experiment 1, three groups of 16 rats received 10 CS-US pairings at 1 trial per day. Group O received a 2-min noise CS that coterminated with a 1-s 0.6-mA grid shock US. Group B recieved a 12-min CS that coterminated with the US. Group A received a 12-min CS that ended 10 min after the US. Groups B and A thus received before-US and after-US extensions, respectively. Experiment 2 was similar except that the US intensity was raised to 0.8 mA, Groups A and B were each assigned 12 rats, and Group O was not included. In general, conditioning declined across Groups O, A, and B, with A and B converging late in training. This convergence is more easily accommodated by a model described by Ayres, Albert, and Bombace (1987) than by SOP (e.g., Wagner, 1981).

Several experiments are conducted on albino rats in an ABA fear renewal paradigm, conditioned fear in the A test context following extinction in context B is studied. Implications for theories of renewal and for clinical practice are discussed.