Biomedical subjects

Mark E Bouton

Publications and source records attributed to Mark E Bouton.

13 recordsLinked to original sources

PubMed2006

Contextual and temporal modulation of extinction: behavioral and biological mechanisms.

Extinction depends, at least partly, on new learning that is specific to the context in which it is learned. Several behavioral phenomena (renewal, reinstatement, spontaneous recovery, and rapid reacquisition) suggest the importance of context in extinction. The present article reviews research on the behavioral and neurobiological mechanisms of contextual influences on extinction learning and retrieval. Contexts appear to select or retrieve the current relationship of the conditional stimulus (CS) with the unconditional stimulus (US), and they are provided by physical background cues, interoceptive drug cues, emotions, recent trials, and the passage of time. The current article pays particular attention to the effects of recent trials and trial spacing. Control of fear extinction by physical context involves interactions between the dorsal hippocampus and the lateral nucleus of the amygdala. This interaction may be mediated by gamma-aminobutyric acid (GABA)-ergic and adrenergic mechanisms.

Amygdala↗

PubMed2006

Intertrial interval as a contextual stimulus.

Four experiments with rats investigated whether the time between appetitive conditioning trials can serve as a discriminative cue for responding during the next conditional stimulus (CS). In Experiment 1, rats that received extinction trials with a 4-min intertrial interval (ITI) showed spontaneous recovery after a retention interval of 16 min, whereas rats that received extinction with a 16-min ITI did not. Experiments 2 and 3 investigated more explicit discriminations between the 4- and 16-min ITIs. When a 16-min ITI signaled that the CS would be reinforced and a 4-min ITI signaled that it would not, the ITIs modulated responding to the CS. But when the 4-min ITI signaled reinforcement and the 16-min ITI did not, there was less evidence of modulation by the ITIs. This asymmetry was due at least partly to a difficulty in performance rather than learning. Experiment 4 investigated similar discriminations with 1- and 4-min ITIs. Here the results took a different form: time in the reinforced ITI elicited responding directly, but did not modulate responding to the CS. ITI can function as a contextual cue, and the results suggest new similarities between the processes behind interval timing and associative learning.

Animals↗

PubMed2006

Effects of bed nucleus of the stria terminalis lesions on conditioned anxiety: aversive conditioning with long-duration conditional stimuli and reinstatement of extinguished fear.

Four experiments investigated the effects of lesions of the bed nucleus of the stria terminalis (BNST) on conditioned fear and anxiety. Though BNST lesions did not disrupt fear conditioning with a short-duration conditional stimulus (CS; Experiments 1 and 3), the lesion attenuated conditioning with a longer duration CS (Experiments 1 and 2). Experiment 3 found that lesions attenuated reinstatement of extinguished fear, which relies on contextual conditioning. Experiment 4 confirmed that the lesion reduced unconditioned anxiety in an elevated zero maze. The authors suggest that long-duration CSs, whether explicit cues or contexts, evoke anxiety conditioned responses, which are dissociable from fear responses to shorter CSs. Results are consistent with behavioral and anatomical distinctions between fear and anxiety and with a behavior-systems view of defensive conditioning.

Analysis of Variance↗

PubMed2006

Priming and trial spacing in extinction: effects on extinction performance, spontaneous recovery, and reinstatement in appetitive conditioning.

Previous research in this laboratory suggests that priming of the conditional stimulus (CS) in short-term memory may play a role in the trial-spacing effects in appetitive conditioning. For example, a non-reinforced presentation of a CS 60 s before a reinforced trial with the same CS produced slower acquisition than a CS presentation that occurred 240 s before the reinforced trial. The results were consistent with the self-generated priming mechanism proposed by Wagner (e.g., Wagner 1978, 1981). The present experiments extended the earlier work by examining the effects of trial spacing in extinction rather than acquisition. After conditioning with a mixture of intertrial intervals (ITIs), rats received extinction with ITIs of 60 or 240 s, longer or shorter values, or different ways of "chunking" extinction trials in time. Although trial spacing produced effects on extinction performance that were consistent with our previous research on acquisition, there were few long-term differences in spontaneous recovery or in reinstatement. Short ITIs in extinction appear to affect extinction performance more than they affect extinction learning. Mechanisms of trial spacing in conditioning and extinction are discussed.

Analysis of Variance↗

PubMed2005

Extinction in multiple contexts does not necessarily make extinction less vulnerable to relapse.

Three fear-conditioning experiments with rat subjects examined the effects of extinction in multiple contexts on a final relapse (renewal) effect that occurred when the extinguished fear cue was tested in a new context (Experiments 1 and 3) or in the context in which fear conditioning had first occurred (Experiment 2). Rats that received extinction in three contexts demonstrated more fear during extinction than rats that received the same number and temporal distribution of extinction trials in one context; extinction was partially lost with each context switch. Although extinction in multiple contexts thus had an impact on extinction behavior, it did not reduce the size of the final renewal effect. Fear during extinction was occasionally positively correlated with fear during final testing, but the two were never negatively correlated. The results suggest that extinction in multiple contexts does not necessarily weaken fear renewal, and that extinction procedures that generate high levels of responding in extinction do not necessarily make extinction learning less context-specific.

Animals↗

PubMed2004

Memory processes in classical conditioning.

Classical conditioning provides a rich and powerful method for studying basic learning, memory, and emotion processes in animals. However, it is important to recognize that an animal's performance in a conditioning experiment provides only an indirect indication of what it has learned. Various remembering and forgetting processes, in addition to other psychological processes, may intervene and complicate what investigators can infer about learning from performance. This article reviews the role of context, interference, and retrieval in a number of classical conditioning phenomena (e.g. extinction), and provides an overview of how long-term and short-term memory processes influence behavior as it is studied in classical conditioning.

Animals↗

PubMed2004

A general role for early onset cues and intra-event learning; comment on McDonald and Siegel (2004).

Research on classical conditioning with drug unconditional stimuli has had a profound effect on the understanding of general conditioning processes. The experiment reported by R. V. McDonald and S. Siegel (see record 2004-10475-001) demonstrates that cues coincident with the onset of an event can become associated with the rest of the event. This sort of learning is probably ubiquitous and has been proposed as a mechanism behind the development of panic disorder, in which interoceptive cues coincident with the start of a panic attack can be associated with the rest of the attack and can eventually come to elicit full-blown panic on their own. Evidence that extinction exposure to early onset cues can reduce their power is especially important. Drug conditioning research continues to provide a powerful testing ground for important general principles of learning.

Conditioning, Classical↗

PubMed2004

Memory priming and trial spacing effects in Pavlovian learning.

Conditioning trials that are massed in time produce less conditioning than those that are spaced in time. Four experiments with rat subjects examined whether a recent conditioning trial interferes with conditioning on the next trial by temporarily "priming" information in short-term memory (e.g., Wagner, 1978, 1981). We used appetitive conditioning procedures in which priming trials preceded target trials by 60 sec. When the priming trials were nonreinforced presentations of a conditioned stimulus (CS), the CS had to be the same CS as the one on the target trial to interfere with conditioning. When priming trials were actual CS-unconditioned stimulus (US) pairings, the CS identity did not matter, the US was the event that interfered with conditioning on the next trial. Reinforced trials reduced performance in a way that did not depend on context blocking. The results suggest that CS and US priming effects do contribute to conditioning deficits observed with massed trial procedures. The results are consistent with Wagner's (1981) "sometimes opponent process," or SOP, model, although a result that is paradoxical for the model suggests that recent USs may have motivational as well as memory effects.

Analysis of Variance↗

PubMed2003

Forward and backward blocking of causal judgment is enhanced by additivity of effect magnitude.

When two causes for a given effect are simultaneously presented, it is natural to expect an effect of greater magnitude. However many laboratory tasks preclude such an additivity rule by imposing a ceiling on effect magnitude-for example, by using a binary outcome. Under these conditions, a compound of two causal cues cannot be distinguished from a compound of one causal cue and one noncausal cue. Two experiments tested the effect of additivity on cue competition. Significant but weak forward blocking and no backward blocking were observed in a conventional "allergy" causal judgment task. Explicit pretraining of magnitude additivity produced strong and significant forward and backward blocking. Additivity pretraining was found to be unnecessary for another cue competition effect, release from overshadowing, which does not logically depend on additivity. The results confirm that blocking is constrained when effect magnitude is constrained and provide support for an inferential account of cue competition.

Adult↗

PubMed2003

Importance of trials versus accumulating time across trials in partially reinforced appetitive conditioning.

Four experiments with rats examined partial reinforcement in appetitive conditioning. In Experiment 1, adding nonreinforced trials to a continuous reinforcement schedule slowed acquisition, whereas deleting reinforcers did not. Trial massing suppressed performance and learning. In Experiment 2, conditioning with a short conditioned stimulus (CS) was rapid, and partial reinforcement with a short CS was as effective as continuous reinforcement with equal accumulated time in the CS. In Experiment 3, conditioning was nevertheless influenced by the probability of reinforcement. In Experiments 3 and 4, conditioning was especially disrupted when nonreinforced trials preceded reinforced trials closely in time. The results underscore the importance of temporal variables in conditioning but are more consistent with trial-based accounts than time-accumulation accounts of conditioning.

Animals↗

PubMed2002

Context, ambiguity, and unlearning: sources of relapse after behavioral extinction.

There is now ample evidence that extinction, the loss of learned performance that occurs when a Pavlovian signal or an instrumental action is repeatedly presented without its reinforcer, does not reflect a destruction of the original learning. This article summarizes the evidence and extends and updates earlier reviews. The main alternative to "unlearning" is the idea that extinction (as well as other retroactive interference processes, including counterconditioning) involves new learning that is stored along with the old. One consequence is that the Pavlovian signal or instrumental action has two available "meanings" and thus has the properties of an ambiguous word: its current meaning (and the resulting behavioral output) depends on what the current context retrieves. Contexts can be provided by a variety of background stimuli, including the physical environment, internal drug state, and time. The second thing learned (e.g., extinction, counterconditioning) seems especially dependent on the context for retrieval. A variety of evidence is consistent with this analysis, which highlights several important sources of relapse after extinction. The article concludes with several issues for future research, among them the question of how we can optimize extinction and other putative "unlearning" treatments so as to prevent the various forms of relapse discussed here.

Anxiety Disorders↗

PubMed2002

The other learning process in substance abuse: comment on Alessi, Roll, Reilly, and Johanson (2002).

The results presented in the article by S. M. Alessi, J. M. Roll, M. P. Reilly, and C.-E. Johanson (2002) suggest that the reinforcing impact of diazepam can change as a function of the participant's experience with the drug. The data fit nicely with a long tradition in learning theory that has shown that the effects of reinforcers can depend crucially on what the organism has been able to learn about them. Often, that learning reflects an associative process like the one involved in Pavlovian conditioning. The hypothesis that preference for diazepam increased in the Alessi et al. study because the drug was associated with money would benefit from additional experiments that include control conditions isolating the role of the Pavlovian drug-money contingency.

Conditioning, Classical↗

PubMedDate not supplied

Context and behavioral processes in extinction.

This article provides a selective review and integration of the behavioral literature on Pavlovian extinction. The first part reviews evidence that extinction does not destroy the original learning, but instead generates new learning that is especially context-dependent. The second part examines insights provided by research on several related behavioral phenomena (the interference paradigms, conditioned inhibition, and inhibition despite reinforcement). The final part examines four potential causes of extinction: the discrimination of a new reinforcement rate, generalization decrement, response inhibition, and violation of a reinforcer expectation. The data are consistent with behavioral models that emphasize the role of generalization decrement and expectation violation, but would be more so if those models were expanded to better accommodate the finding that extinction involves a context-modulated form of inhibitory learning.

Animals↗