Multimodal classical conditioning of fear: contributions of direct, observational, and verbal experiences to current fears

The authors propose that a multimodal classical conditioning model be considered when clinicians or clinical researchers study the etiology of fears and anxieties learned by human beings. They argue that fears can be built through the combined effects of direct, observed, and verbally presented classical conditioning trials. Multimodal classical conditioning is offered as an alternative to the three pathways to fear argument prominent in the human fear literature. In contrast to the three pathways position, the authors present theoretical arguments for why "learning by observation" and "learning through the receipt of verbal information" should be considered classical conditioning through observational and verbal modes. The paper includes a demonstration of how data, commonly collected in research on the three pathways to fear, would be studied differently using a multimodal classical conditioning perspective. Finally, the authors discuss implications for assessment, treatment, and prevention of learned fears in humans.     

Conditioning, expectancy, and the placebo effect: comment on Stewart-Williams and Podd (2004)

Classical conditioning is included as a component in the response expectancy model of placebo responding. Though introspectable when attention is drawn to them, expectancies need not be in awareness while guiding behavior. Most placebo effects are linked to expectancies, and classical conditioning is one factor (but not the only factor) by which these expectancies can be produced and altered. Conditioned placebo effects without expectancies exist but are relatively rare in humans. The adaptive advantage of cognition is increased response flexibility. For it to convey that benefit, however, it must be capable of overriding the influence of simpler automatic processes. Thus, the higher up the phylogenetic scale, the smaller the role of nonconscious conditioning processes and the larger the role of cognition.     

A conceptual and theoretical analysis of evaluative conditioning

Evaluative conditioning is best defined as an effect, that is, as a change in the valence of a stimulus that results from pairing the stimulus with another stimulus. This definition has several advantages that are made explicit in this paper. One of the advantages is that it clarifies that evaluative conditioning can be due to multiple processes. Therefore, the conditions under which evaluative conditioning is observed can depend on the processes that underlie a particular manifestation of evaluative conditioning. This could explain why there are so many conflicting results about the conditions under which evaluative conditioning can be found. Future research should adopt a meta-conditional approach that focuses not only on whether a certain condition is crucial for obtaining evaluative conditioning but should also examine when a certain condition is crucial.     

Uncertainty, as defined by the contingency between environmental events, and the adrenocortical response of the rat to electric shock

The pituitary-adrenal system is thought to be sensitive to the degree of uncertainty in a situation. In addition, there is some question whether the pituitary-adrenal system can be conditioned in a Pavlovian sense. Three experiments are reported here. The first and third sought to define uncertainty in terms of conditioned stimulus-unconditioned stimulus (CB-US) and US-US contingencies, which vary the amount of information that can be used to predict the occurrence of discrete shocks. The second experiment examined the possibility that the adrenocortical system was subject to the laws of Pavlovian conditioning, by using a conditioned emotional response paradigm. The results showed that the magnitude of the Pituitary-adrenal response varied in a curvilinear manner along the dimension of uncertainty. Very low and very high degrees of uncertainty resulted in greater corticosterone elevations than did moderate levels. No evidence for Pavlovian conditioning of the adrencortical system was found, although behavioral measures showed fear conditioning. The data presented were supportive of the hypothesis that the pituitary-adrenal response reflects the operation of an arousal system.     

Conditional reflexes and sensory-evoked epilepsy: The nature of the therapeutic process

Studies of conditional reflex therapy for patients with sensory-evoked epilepsy are reviewed and experimental studies in animals reported. The behavioral methods employed in the therapy are reviewed. They are of a conditioning nature and are defined as clinical therapeutic conditioning. Sensory-evoked epilepsy can be induced in animals by conditioning techniques, provided the animal brain has been rendered epileptogenic. Sensory-evoked epilepsy in patients can be made worse by conditioning, and can be changed from one type to another. However, sensory-evoked seizures in humans are not the result of conditional reflexes.     

Ideational conditioning: bridging the cognitive-behaviourist divide

Classical conditioning has traditionally been referred to as a 'dumb form of learning'; however, psychological activity can be redefined in terms of the conditioned reflex by considering other more complex forms of conditioning, i.e., configural or semantic conditioning. In this paper it is argued that conditioning may underpin both human perception and consciousness and previous experiments involving perceptual conditioning are outlined. Recent experiments which involve a new paradigm of ideational conditioning have shown that cognitions can play a part in conditioning processes. It is shown here that ideational conditioning demonstrates unequivocally that thoughts alone are adequate stimuli for acquisition of behavioural responses and that these experiments may help to bridge the cognitive-behaviourist divide.     

Massed and spaced learning in honeybees: the role of CS, US, the intertrial interval, and the test interval

Conditioning the proboscis extension reflex of harnessed honeybees (Apis mellifera) is used to study the effect temporal spacing between successive conditioning trials has on memory. Retention is monitored at two long-term intervals corresponding to early (1 and 2 d after conditioning) and late long-term memory (3 and 4 d). The acquisition level is varied by using different conditioned stimuli (odors, mechanical stimulation, and temperature increase at the antenna), varying strengths of the unconditioned stimulus (sucrose), and various numbers of conditioning trials. How learning trials are spaced is the dominant factor both for acquisition and retention, and although longer intertrial intervals lead to better acquisition and higher retention, the level of acquisition per se does not determine the spacing effect on retention. Rather, spaced conditioning leads to higher memory consolidation both during acquisition and later, between the early and long-term memory phases. These consolidation processes can be selectively inhibited by blocking protein synthesis during acquisition.     

Classical conditioning,awareness, and brain systems

Memory is composed of several different abilities that are supported by different brain systems. The distinction between declarative (conscious) and nondeclarative (non-conscious) memory has proved useful in understanding the nature of eyeblink classical conditioning – the best understood example of classical conditioning in vertebrates. In delay conditioning, the standard procedure, conditioning depends on the cerebellum and brainstem and is intact in amnesia. Trace conditioning, a variant of the standard procedure, depends additionally on the hippocampus and neocortex and is impaired in amnesia. Recent studies have sharpened the contrast between delay and trace conditioning by exploring the importance of awareness. We discuss these new findings in relation to the brain systems supporting eyeblink conditioning and suggest why awareness is important for trace conditioning but not for delay conditioning.     

Conjunctive representations,the hippocampus,and contextual fear conditioning

The context in which events occur can be represented as both (1) a set of independent features, the feature representation view, and (2) a set of features bound into a unitary representation, the conjunction representation view. It is assumed that extrahippocampal (e.g., neocortical) areas provide a basis for feature representations, but the hippocampal formation makes an essential contribution to the automatic storage of conjunctive representations. We develop this dual-representation view and explore its implications for hippocampal contributions to contextual fear conditioning processes. To this end, we discuss how our framework can resolve some of the conflicts in the recent literature relating the hippocampus to contextual fear conditioning. We also present new data supporting the role of a key mechanism afforded by conjunctive representations—pattern completion (the ability of a subset of a memory pattern to activate the complete memory)—in contextual fear conditioning. As is implied by this mechanism, we report that fear can be conditioned to the memory representation of a context that is not actually present at the time of shock. Moreover, this result is predicted by our computational model of cortical and hippocampal function. We suggest that pattern completion demonstrated in animals and by our model provides a mechanistic bridge to human declarative memory.     

Human evaluative conditioning: acquisition trials, presentation schedule, evaluative style and contingency awareness.

Two different processes may be operative in human Pavlovian conditioning: signal learning and evaluative learning. Whereas most studies on evaluative conditioning focused on a mere demonstration of the phenomenon or on a theoretical analysis of the underlying processes, some basic parameters of evaluative learning are still unexplored. Hence, using the standard neutral picture--(dis)liked picture pairing paradigm (Baeyens, Eelen & Van den Bergh, 1990), in this study the effect of two parameters of evaluative conditioning was assessed on a between-subjects base, namely the Number of Acquisition Trials (2/5/10/20) and the Presentation Schedule of the stimulus pairs (blockwise or random). Additionally, the study included an exploratory analysis of the potential effects of the Evaluative Style of subjects (Feelers vs Thinkers, operationalized in terms of speed of emitting evaluations). Finally, the relationship between contingency awareness and evaluative learning was reassessed. Neutral-liked conditioning was found to be quadratically related to the number of acquisition trials (increase in effect up to 10 trials, decrease from 10 to 20 trials), whereas neutral-disliked conditioning linearly increased with increasing numbers of trials. Randomized vs blockwise presentation schedules of the stimulus pairs did differentially affect the overall pattern of conditioning, but in a way which was both unexpected and difficult to account for theoretically. Both the Evaluative Style of subjects and contingency awareness were demonstrated to be generally orthogonal to conditioned shifts in CS valence. Based on these findings, some practical suggestions are provided for the application of evaluating conditioning based therapeutical interventions to affective-behavioral disorders which are centred around inappropriate (dis)likes.     

A neural model of normal and abnormal learning and memory consolidation: adaptively timed conditioning,hippocampus, amnesia,neurotrophins, and consciousness

How do the hippocampus and amygdala interact with thalamocortical systems to regulate cognitive and cognitive-emotional learning? Why do lesions of thalamus, amygdala, hippocampus, and cortex have differential effects depending on the phase of learning when they occur? In particular, why is the hippocampus typically needed for trace conditioning, but not delay conditioning, and what do the exceptions reveal? Why do amygdala lesions made before or immediately after training decelerate conditioning while those made later do not? Why do thalamic or sensory cortical lesions degrade trace conditioning more than delay conditioning? Why do hippocampal lesions during trace conditioning experiments degrade recent but not temporally remote learning? Why do orbitofrontal cortical lesions degrade temporally remote but not recent or post-lesion learning? How is temporally graded amnesia caused by ablation of prefrontal cortex after memory consolidation? How are attention and consciousness linked during conditioning? How do neurotrophins, notably brain-derived neurotrophic factor (BDNF), influence memory formation and consolidation? Is there a common output path for learned performance? A neural model proposes a unified answer to these questions that overcome problems of alternative memory models.     

A microprocessor control system and solid state interface for controlling electrophysiological studies of conditioning

This paper describes a microprocessor control system and solid state interface for controlling the apparatus in combined behavioral-electrophysiological studies of conditioning. The computer program, which is designed to control classical conditioning of the rabbit’s nictitating membrane response, provides the flexibility to control all conditioning parameters (e.g., interstimulus and intertrial intervals, trial type, and sequence of trial types) with only minor modifications. The system is free from artifacts that can distort electrophysiological recordings and can easily be modified to accommodate other behavioral paradigms in which electrophysiological responses are recorded.     

Using pavlovian higher-order conditioning paradigms to investigate the neural substrates of emotional learning and memory

In first-order Pavlovian conditioning, learning is acquired by pairing a conditioned stimulus (CS) with an intrinsically motivating unconditioned stimulus (US; e.g., food or shock). In higher-order Pavlovian conditioning (sensory preconditioning and second-order conditioning), the CS is paired with a stimulus that has motivational value that is acquired rather than intrinsic. This review describes some of the ways higher-order conditioning paradigms can be used to elucidate substrates of learning and memory, primarily focusing on fear conditioning. First-order conditioning, second-order conditioning, and sensory preconditioning allow for the controlled demonstration of three distinct forms of memory, the neural substrates of which can thus be analyzed. Higher-order conditioning phenomena allow one to distinguish more precisely between processes involved in transmission of sensory or motor information and processes involved in the plasticity underlying learning. Finally, higher-order conditioning paradigms may also allow one to distinguish between processes involved in behavioral expression of memory retrieval versus processes involved in memory retrieval itself.     

Emotion, attention, and the startle reflex

This theoretical model of emotion is based on research using the startle-probe methodology. It explains inconsistencies in probe studies of attention and fear conditioning and provides a new approach to emotional perception, imagery, and memory. Emotions are organized biphasically, as appetitive or aversive (defensive). Reflexes with the same valence as an ongoing emotional state are augmented; mismatched reflexes are inhibited. Thus, the startle response (an aversive reflex) is enhanced during a fear state and is diminished in a pleasant emotional context. This affect-startle effect is not determined by general arousal, simple attention, or probe modality. The effect is found when affects are prompted by pictures or memory images, changes appropriately with aversive conditioning, and may be dependent on right-hemisphere processing. Implications for clinical, neurophysiological, and basic research in emotion are outlined.     

ENURESIS CONTROL THROUGH FADING,ESCAPE, AND AVOIDANCE TRAINING

A twin-signal device that provides both escape and avoidance conditioning in enuresis control is described involving a procedure documented by two case studies. In addition, a technique of fading as an adjunct to the process is utilized with one subject. The results indicate that a combination of operant and respondent conditioning involving escape and avoidance training may be an improvement over the more traditional conditioning procedure.     

Exteroceptive context in tasteaversion conditioning and extinction: odour, cage, and bottle stimuli

Five experiments investigated the extent to which the exteroceptive context, present on a saccharin aversion conditioning trial with rats, controlled the resulting aversion on one-bottle extinction tests and subsequent preference tests. The presence or absence of the specific odour which had been present on the conditioning trial was found not to influence saccharin intake on extinction tests, whereas the presence of the particular compartment in which, and the bottle from which, the saccharin had been consumed greatly suppressed saccharin intake as compared to the absence of these elements. Preference tests, performed in the respective conditioning contexts, showed extinction to be specific to the compartment + bottle context: groups that had extinguished their saccharin aversion in a context different from the conditioning context, retained their aversion in the conditioning context. No such specificity was found for the odour context. However, in the absence of the taste stimulus during the extinction phase, the odour that had been present on the conditioning trial did control the amount of water consumed, whereas the compartment+bottle context did not. Moreover, on preference tests, groups that had consumed water during extinction in the presence of the odour context, evidenced a lesser saccharin aversion than groups not exposed to the odour. The results are interpreted as demonstrating that rats learn about taste, odour, cage and bottle stimuli on a taste-aversion conditioning trial, and that taste and bottle stimuli seem to be the most salient.     

Associative learning of likes and dislikes: a review of 25 years of research on human evaluative conditioning.

Evaluative conditioning refers to changes in the liking of a stimulus that are due to the fact that the stimulus has been paired with other, positive or negative stimuli. Although evaluative conditioning appears to be subjected to certain boundary conditions, significant evaluative conditioning effects have been obtained using a large variety of stimuli and procedures. Some data suggest that evaluative conditioning can occur under conditions that do not support other forms of Pavlovian conditioning, and several models have been proposed to account for these differences. In the present article, the authors summarize the available literature, draw conclusions where possible, and provide suggestions for future research.