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Cue exposure and learning theory.

The implications are discussed for cue exposure treatment of four theoretical issues; (a) spontaneous recovery, (b) response competition, (c) generalization, and (d) the cognitive basis of conditioning. It is suggested that practical cue exposure treatment will not be as straight-forward as initial trials have suggested.

Alcoholism↗

Extinguishing conditioned responses during opiate dependence treatment turning laboratory findings into clinical procedures.

Former opiate addicts (even those who have remained drug-free for several months) often report symptoms of opiate withdrawal (eg. nausea, gooseflesh, etc.) and/or intense drug craving when exposed to stimuli previously associated with the act of drug injection. This phenomenon of learned or "conditioned" withdrawal/craving is widely reported and is potentially important in explaining relapse to drug use. However, no effective, clinically applicable intervention had been available to "extinguish" these conditioned phenomena. An ongoing project to develop such an intervention has revealed: Conditioned withdrawal and craving are pervasive among both methadone maintained patients (even though actual physical withdrawal is blocked) and drug-free patients even after 30 days of inpatient Therapeutic Community rehabilitation. Conditioned withdrawal and craving can be effectively extinguished in an intensive, three-week, inpatient procedure. Emotional states such as anger, depression and anxiety can elicit and exacerbate conditioned withdrawal and craving. They may also act as an integral part of a conditioned stimulus complex. The authors discuss the problems associated with turning a laboratory-based procedure into a clinical intervention. Encouraging preliminary results from an integrated treatment "package" are presented.

Behavior Therapy↗

A comparison of Lewis and Fischer rat strains on autoshaping (sign-tracking), discrimination reversal learning and negative auto-maintenance.

Lewis (LEW) and Fischer (F344) rat strains differ on a number of physiological characteristics, such as hypothalamic-pituitary-adrenal (HPA) axis activity, as well as on behavioral tasks, including those that measure impulsivity and drug reward. Since autoshaping, the phenomenon where animals approach and contact reward-paired conditioned stimuli, has been linked to HPA axis functioning, impulsivity and drug taking, the present study compared LEW and F344 rats on the rate of acquisition and performance of the autoshaping response. Rats were trained on an autoshaping procedure where insertions of one retractable lever (CS(+)) were paired response-independently with food, while insertions of another lever (CS(-)) were not paired with food. LEW rats acquired the autoshaping response more rapidly and also performed the autoshaping response at a higher rate than F344 rats. No differences between the strains were observed when rats were trained on a discrimination reversal where the CS(+) and CS(-) levers were reversed or during a negative auto-maintenance phase where CS(+) lever contacts cancelled food delivery. Potential physiological mechanisms that might mediate the present results, including strain differences in HPA axis and monoamine neurotransmitter activity, are discussed. The finding that LEW (as compared to F344 rats) more readily acquire autoshaping and perform more responses is consistent with research indicating that LEW rats behave more impulsively and more readily self-administer drugs of abuse.

Analysis of Variance↗

I don't like it because it eats sprouts: conditioning preferences in children.

Although little is known about how preferences develop in childhood, work in adults suggests that evaluative responses to stimuli can be acquired through classical conditioning. In two experiments children were exposed to novel cartoon characters, that were either consistently paired with a picture of a disliked food (Brussels sprouts) or a liked food (ice cream). Relative preferences for these stimuli (and others) were measured before and after these paired presentations (Experiment 1): preferences for the cartoon character paired with Brussels sprouts decreased, whereas preferences for the character paired with ice cream increased. These preferences persisted after 10 un-reinforced trials. Experiment 2 replicated this finding using affective priming as an index of preference for the cartoon characters. These findings demonstrate that preferences to novel stimuli can be conditioned in children and result from associations formed between the stimulus and a stimulus possessing positive or negative valence.

Analysis of Variance↗

Invertebrate learning: what can't a worm learn?

The nematode worm Caenorhabditis elegans can learn and remember the stimuli it encounters, the environment it is in, and its own physiological state. Analyses of mutations in C. elegans that affect different aspects of experience are beginning to address the nature of learning.

Animals↗

Increased c-Fos expression in the medial part of the lateral habenula during cue-evoked heroin-seeking in rats.

Conditioned environmental stimuli are known to be important determinants of drug seeking behavior. c-Fos, the protein product of the protooncogene c-Fos, is expressed in neurons when there are drug-associated cue-induced drug-seeking behaviour. Therefore, its expression could serve as a marker of regional neuronal activation. Using an extinction/reinstatement paradigm of relapse animal model, we trained Sprague-Dawley rats to nose-poke for i.v. heroin (0.05 mg/kg/infusion) either daily for 4h or 25 infusions for 14 consecutive days. We then tested these animals for cue-evoked heroin-seeking behavior after abstinence from self-administration of heroin for 14 days. Expression of c-Fos was examined in the lateral habenula (LHb), a region important for conveying information between the limbic forebrain and midbrain. Findings showed that heroin-associated conditioned stimuli could induce robust heroin-seeking behavior that was associated with increased c-Fos immunoreactivity in the medial part of the LHb. This observation suggests the involvement of the LHb in mediating drug cue-induced heroin-seeking behavior after abstinence from self-administration of heroin.

Animals↗

Current approaches to etiology and pathophysiology of specific phobia.

Specific phobia is a common, heterogeneous disorder whose central feature is persistent, unreasonable fear of a circumscribed object or situation. This article reviews current etiological theories and empirical data that seem likely to be important in investigating the pathophysiology of this disorder. These include conditioning, modified conditioning, and nonassociative models of phobia development, physiological response to the phobic stimulus, neuroimaging, primate, and biological challenge studies. Pathophysiological hypotheses suggested by recent research on the neurocircuitry of conditioned fear are also discussed. Though specific phobias have been of less public health and clinical interest than other anxiety disorders, their circumscribed nature and possible relationship to conditioned fear may make them a productive subject for research into basic pathophysiology.

Animals↗

Hebb, pandemonium and catastrophic hypermnesia: the hippocampus as a suppressor of inappropriate associations.

The hippocampus has been proposed as a key component of a "behavioural inhibition system". We explore the implications of this idea for the nature of associative memory--i.e. learning that is distinct from the moulding of response sequences by error correction and reinforcement. It leads to the view that all associative memory depends on purely Hebbian mechanisms. Memories involve acquisition of new goals not the strengthening of new stimulus-response links. Critically, memories will consist of affectively positive and affectively negative associations as well "purely cognitive" information. The hippocampus is seen as a supervisor that is normally "just checking" information about current available goals. When one available goal is pre-eminent there is no hippocampal output and the goal controls the response system. When two or more goals are similarly and highly primed there is conflict. This is detected by the hippocampus which sends output that increases the valence of affectively negative perceptions and so resolves the conflict by suppressing more aversive goals. Such conflict resolution occurs with innate as well as acquired goals and is fundamentally non-memorial. But, in memory paradigms, it can often act to suppress interference on the current trial and, through Hebbian association of the increase in negative affect, decrease the probability of interference on later trials and during consolidation. Both memory-driven and innate behaviour is made hippocampal-dependent by innate and acquired conflicting tendencies and not the class of stimulus presented.

Amnesia↗

Prolonged exposure counterconditioning as a treatment for chronic posttraumatic stress disorder.

A counterconditioning model is presented from which the behavioral treatment prolonged exposure counterconditioning (PEC) was developed. The first part of a PEC session is intended to increase trauma exposure tolerance and counter numbing symptoms, the second to elicit trauma responses fully, and the third to weaken trauma responses. The first client with chronic posttraumatic stress disorder (PTSD) who was treated with PEC is presented. A statistical technique for analyzing single-case subject designs was used to evaluate the treatment. PEC effectively decreased the client's PTSD and associated psychopathology. Crucial differences between PEC and other behavioral treatments are discussed. An associative functional model is presented as a potentially useful conceptualization of PTSD, depression, and other anxiety disorders.

Behavior Therapy↗

Treatment of specific phobias with Eye Movement Desensitization and Reprocessing (EMDR): protocol, empirical status, and conceptual issues.

This paper considers the current empirical status of Eye Movement Desensitization and Reprocessing (EMDR) as a treatment method for specific phobias, along with some conceptual and practical issues in relation to its use. Both uncontrolled and controlled studies on the application of EMDR with specific phobias demonstrate that EMDR can produce significant improvements within a limited number of sessions. With regard to the treatment of childhood spider phobia, EMDR has been found to be more effective than a placebo control condition, but less effective than exposure in vivo. The empirical support for EMDR with specific phobias is still meagre, therefore, one should remain cautious. However, given that there is insufficient research to validate any method for complex or trauma related phobias, that EMDR is a time-limited procedure, and that it can be used in cases for which an exposure in vivo approach is difficult to administer, the application of EMDR with specific phobias merits further clinical and research attention.

Adult↗

Unconscious learning. Conditioning to subliminal visual stimuli.

The role of consciousness in Pavlovian conditioning was examined in two experiments in which visually masked neutral words were used as the conditioned stimuli (CS) and an electric shock as the unconditioned stimulus (US). The inter-stimulus interval (ISI) was established individually. A detection threshold was used in Experiment 1 and an identification threshold in Experiment 2. The primary dependent variable was the skin conductance response (SCR). Results showed that the conditioned response (CR) was acquired by 58% of participants who perceived stimuli above the identification threshold, 50% of participants who perceived stimuli below the detection threshold, and 11% of participants who perceived stimuli below the identification threshold, but above the detection threshold. These results suggest that consciousness of the CS-US contingency is not a necessary condition for acquiring a CR of the autonomous nervous system (ANS).

Adolescent↗

Heterochronous involvement of neurotrophic factors in the neurochemical organization of learning and memory processes in adult organisms.

Studies were performed on the involvement of neurotrophic factors in the neurochemical mechanisms of the integrative functions of the brain. The effects of various intrahippocampal doses of antibodies to neurotrophic factors--protein S100 and lectin CSL--were studied on the formation, retention, and reproduction of a habituated acoustic startle response and conditioned fear in adult rats. S100b contents in the hippocampus, hypothalamus, frontal cortex, and cerebellar hemispheres and vermis, and in the basal nuclei were measured in rat brains 0.5, 1, 2, 4, 6, 8, 24, and 48 h after long-term habituation to the startle response. Antibodies to neurotrophic factors had selective and dose-dependent effects on the different memory and learning processes underlying these types of behavior. Changes in S100b in brain structures were seen, which were specific in terms of quantitative levels and dynamics, after acquisition of the behavioral habit. The results obtained here, along with previously reported data on the effects of antibodies to S100b and CSL given into the cerebellum, are discussed as experimental support for the hypothesis of the heterochronous neurochemical organization of integrative brain activity.

Analysis of Variance↗