The Effect of a Discrete Signal on Context Conditioning: Assessment by Preference and Freezing Tests

Maes, J.H.R.; LoLordo, Vincent M.

doi:10.1006/lmot.1996.0025

Cited by 6 publications

(2 citation statements)

References 34 publications

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“…Some of our own indirect evidence suggests that these C57/bl6 mice extinguish context fear faster than cue fear (Cain et al 2002). However, other investigators have also failed to find increases in context freezing with more CS-alone presentations in experiments designed to reveal them (Maes and LoLordo 1996), and we have been unable to find any observations of this expected reciprocal increase in context conditioning with degraded CS contingency. Thus, while the orderly pattern of decreasing response to the cue with reduced contingency in our experiments suggests that cue competition should have taken place, it was not expressed as context freezing.…”

Section: Discussioncontrasting

confidence: 60%

The L-type calcium channel blocker nifedipine impairs extinction, but not reduced contingency effects, in mice

Cain

Godsil²,

Jami³

et al. 2005

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We recently reported that fear extinction, a form of inhibitory learning, is selectively blocked by systemic administration of L-type voltage-gated calcium channel (LVGCC) antagonists, including nifedipine, in mice. We here replicate this finding and examine three reduced contingency effects after vehicle or nifedipine (40 mg/kg) administration. In the first experiment, contingency reduction was achieved by adding USs to the training protocol (degraded contingency), a phenomenon thought to be independent of behavioral inhibition. In the second experiment, contingency reduction was achieved by varying the percentage of CS-US pairing, a phenomenon thought to be weakly dependent on behavioral inhibition. In the third and fourth experiments, contingency reduction was achieved by adding CSs to the training protocol (partial reinforcement), a phenomenon thought to be completely dependent on behavioral inhibition. We found that none of these reduced contingency effects was impaired by nifedipine. In a final experiment, we found that extinction conducted 1 or 3 h post-acquisition, but not immediately, was LVGCC-dependent. Taken together, the results suggest that reduced contingency effects and extinction depend on different molecular mechanisms and that LVGCC dependence of behavioral inhibition develops with time after associative CS-US learning.Pavlovian fear conditioning in rodents has been widely used in the laboratory setting to model human fear and anxiety, as well as excitatory learning and memory processes (Fendt and Fanselow 1999;Maren 2001;Ohman and Mineka 2001;Fanselow and Gale 2003;LeDoux 2003). Fear conditioning is achieved by temporally pairing an initially neutral conditional stimulus (CS), such as a tone, with an aversive unconditional stimulus (US), usually a mild footshock. Rats show robust fear responding to a CS with as little as one CS-US pairing (Fanselow 1990). Extinction of conditional fear, the progressive weakening of the fear response by repeated presentations of the CS alone, has been an important model in the development of behavior therapy for human anxiety disorders (Wolpe 1969;Wolpe and Rowan 1988;Craske 1999;Myers and Davis 2002) and is the prototypical procedure for inducing inhibitory learning (Davis et al. 2003;Delamater 2004).While the molecular and cellular mechanisms of fear acquisition have been intensely studied for decades, the mechanisms of fear extinction are only beginning to be unraveled. For instance, lesion and local infusion studies suggest that the amygdala (Falls et al. 1992;Quirk et al. 1997;Lu et al. 2001;Marsicano et al. 2002;Royer and Pare 2002;Walker et al. 2002;Davis et al. 2003;Ledgerwood et al. 2003; Lin et al. 2003a,b,c) and prefrontal cortex (Morgan et al. 1993;Quirk et al. 2000;Herry and Garcia 2002;Milad and Quirk 2002;Santini et al. 2004;Shah et al. 2004) participate in the learning and retention of fear extinction. Additionally, both local infusion and systemic behavioral pharmacology studies have identified important roles in extinction for the NMDA-type ...

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Section: Discussioncontrasting

confidence: 60%

The L-type calcium channel blocker nifedipine impairs extinction, but not reduced contingency effects, in mice

Cain

Godsil²,

Jami³

et al. 2005

Learn. Mem.

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“…However, he observed substantial though incomplete overshadowing after 12 sessions. Moreover, in an experiment otherwise like Experiment 2, but with a single conditioning session, there was no overshadowing of situational cues by the discrete CS even with variable intervals between trials (see also Maes & LoLordo, 1996). Whether more conditioning trials in the one trial per session procedure of Experiment 1 would have revealed overshadowing in the variable time groups remains to be seen.…”

Section: Discussionmentioning

confidence: 84%

Overshadowing of situational cues with variable but not fixed intertrial intervals

LoLordo

Williams

McPhee

2001

Animal Learning & Behavior

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In two experiments, we examined the conditions under which signaling an unconditioned stimulus (US) with a nominal conditioned stimulus (CS) interferes with the conditioning of situational cues in defensive freezing in the rat. Subjects received footshock USs that were (1) either signaled or unsignaled and (2) either varied or fixed in their temporal location within the conditioning session. Experiment 1, with only one trial per session, yielded no evidence that signaling affected pretrial freezing using either a fixed or variable interval between placement in the context and shock onset. In a test in which no CSs or footshocks were presented, groups that previously had received footshock at a fixed temporal location showed greatest freezing at around that same time. For groups that had received footshocks at various times, freezing declined across the test session. Experiment 2 showed overshadowing of pretrial freezing after more extensive conditioning with many trials per session, but only if the intershock intervals were variable rather than fixed.

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No Sex Difference in Contextual Control over the Expression of Latent Inhibition and Extinction in Pavlovian Fear Conditioning in Rats

Maes

2002

Neurobiology of Learning and Memory

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The Effect of a Discrete Signal on Context Conditioning: Assessment by Preference and Freezing Tests

Cited by 6 publications

References 34 publications

The L-type calcium channel blocker nifedipine impairs extinction, but not reduced contingency effects, in mice

The L-type calcium channel blocker nifedipine impairs extinction, but not reduced contingency effects, in mice

Overshadowing of situational cues with variable but not fixed intertrial intervals

No Sex Difference in Contextual Control over the Expression of Latent Inhibition and Extinction in Pavlovian Fear Conditioning in Rats

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