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At least 343 records · Page 19Linked to original sources
PubMed1991

Effects of ritanserin on aversive classical conditioning in humans.

According to one formulation of the behavioural functions of 5HT, aversive conditioned stimuli mediate their behavioural and emotional effects through activation of 5HT projections from dorsal raphe nucleus to receptors of the 5HT2 family in amygdala and elsewhere. To test this theory in humans, groups of ten normal volunteers received placebo, the 5HT2 lc antagonist ritanserin (10 mg PO) and no pill. Ritanserin had no effect on skin conductance level, variability (spontaneous fluctuations) or habituation to a sequence of ten neutral tones. After a conditioning trial in which tone 11 was followed by an aversive white noise, skin conductance responses to a further ten tones were enhanced. This effect was abolished by ritanserin. The results indicate a selective involvement of 5HT2/lc receptors in modulating aversively conditioned skin conductance responses.

Adult↗
PubMed1994

Alcohol as an unconditioned stimulus in human classical conditioning.

Recent experiments with human subjects have shown that drug cues (e.g. sight of beer or needle and syringe) elicit different responses than do neutral stimuli. However, because conditioning has not been carried out in the majority of cases, it is not clear why drug cues have different response eliciting capacities; associative and nonassociative mechanisms may both play a part. In this experiment a counterbalanced differential conditioning procedure was used to isolate the role of associative processes in the development of physiological, behavioural, and subjective conditioned responses to cues for alcohol over the course of repeated conditioning sessions. Twelve healthy volunteers took part in the experiment which involved each subject attending for ten sessions. On physiological measures evidence was found for conditioning of skin conductance and cardiac inter-beat interval responses to cues for alcohol delivery. Over the course of conditioning on behavioural measures of drink consumption there were changes in the rate of consumption and number of sips taken as a function of whether or not the drinks contained alcohol. Finally, on subjective measures, there was a differential change in subjective state in response to alcohol and soft drink expectancy as conditioning progressed.

Adult↗
PubMed1995

Sensitization to apomorphine in pigeons: unaffected by latent inhibition but still due to classical conditioning.

When administered apomorphine, pigeons exhibit protracted bouts of pecking behavior. This response is subject to sensitization, as it initially increases with repeated drug injections. The hypothesis is examined that the sensitization is due to a Pavlovian conditioning of the drug-induced pecking to the environment in which it first takes effect. In a first experiment, we attempted to suppress this conditioning by extensively pre-exposing the birds to the test environment and saline injections (latent inhibition procedure). As the experiment yielded undiminished sensitization, it cast doubt on the conditioning hypothesis. However, while inhibitory pretraining also proved ineffective in a second experiment, a shortening of response latencies specific to the environment in which the animals had first experienced the apomorphine effect supported the conditioning hypothesis. It is suggested that the absence of latent inhibition may be due to the interference of a context-dependent conditioning effect. A third experiment that examined the hypothesis that the reinforcing properties of apomorphine might be attributable to its well known anorectic properties. The results provided some support for this notion. At the same time, they also confirmed that apomorphine-induced pecking conditions reliably to environmental cues. These cues are then by themselves capable of provoking conditioned pecking.

Animals↗
PubMedDate not supplied

Human classical conditioning. The status of the CS.

Recent reports of failure to obtain blocking in human galvanic skin response (GSR) conditioning, together with our own equivocal results with eyelid conditioning, have motivated us to re-examine the status of the conditioned stimulus (CS) in human conditioning studies. The issues raised by compound stimuli, by contextual cues and occasion setting stimuli, and by cross-modal transfer are considered in the light of data from our laboratories. These data include observations on the interchangeability of stimulus modalities during acquisition, the use of varying information loads embedded in occasion setting displays, the comparison of alternative blocking designs and the analysis of response topography in relation to stimulus variability. They suggested that an adequate account of the CS in human conditioning studies must recognize that it is dynamically processed and reprocessed both during and after acquisition.

Arousal↗
PubMedDate not supplied

Electrodermal activity as an indicator of information processing in a nonaversive differential classical conditioning paradigm.

Most investigations of information processing in human Pavlovian autonomic conditioning focussed on the role of awareness of the contingency of the conditioned stimulus (CS) and the unconditioned stimulus (UCS). While in these studies only the qualitative information of the CS (UCS occurring vs not occurring) was varied, the present experiment was designed to vary the quantitative information of the CS. In a differential conditioning paradigm, using a letter reproduction task as nonaversive UCS, electrodermal responses to different degrees of CS information content were investigated. Twenty subjects experienced two different conditions in a within subject design. In one condition only the number of letters used in the following UCS was presented as CS+, while in the other condition the CS already contained the whole UCS information. Both conditions led to significant differences in magnitudes of electrodermal responding.

Adult↗
PubMedDate not supplied

Covariation bias, classical conditioning, and phobic fear.

The present study investigated whether phobics show an illusory correlation (IC) between phobia-relevant stimuli and aversive events. Nineteen treated and 19 untreated spider phobics were exposed to a series of 72 slides. Three different categories were used: Phobia-relevant slides (spiders), alternative fear-relevant slides (weapons), and neutral slides (flowers). Slides were randomly paired with either a shock, a siren, or nothing at all. All slide/outcome combinations occurred equally frequently. A posteriori recorded contingency estimates indicated that untreated phobics dramatically overestimate the covariation of spiders and shock. On-line recorded outcome expectancies revealed that the bias to overestimate the spider-shock contingency is highly resistant to extinction. The covariation bias was accompanied by differentially heightened electrodermal first interval responses (FIR) and unconditioned electrodermal responses (third interval responses: TIR) on phobia-relevant trials. Treated phobics did not show a covariation bias, indicating that such bias can be modulated by behavioral treatment. The present findings sustain the hypothesis that phobic subjects process information in a fear-confirming way.

Adult↗
PubMedDate not supplied

Constraint, alcoholism, and electrodermal response in aversive classical conditioning and mismatch novelty paradigms.

This study investigated whether low levels of the personality trait of constraint and early-onset alcoholism would be associated with deficits in aversive conditioning and smaller responses to novelty in a stimulus mismatch protocol. Personality traits (constraint and socialization) and skin conductance responses (SCRs) during conditioning and novelty paradigms were assessed in alcoholics (n=41) and non-alcoholics (n = 32). The conditioning protocol involved measuring SCRs after conditioned stimuli (CS+: tones) paired with shock, CS- tones unpaired with shock, and CS+ probes unpaired with shock. The mismatch protocol involved measuring SCRs to auditory stimuli consisting of a series of 5 pure tones of the same pitch followed a shorter white noise stimulus (the novel stimulus). Contrary to the hypothesis, alcoholics did not differ from non-alcoholics in SCRs to CS+ probes or on the mismatch measure (SCR novel tone-SCR to 5th tone). Higher levels of constraint and self-reports of fear during conditioning were associated with smaller responses to both the CS+ probes and the CS- tones as well as the mismatch measure within non-alcoholics, but not within alcoholics. In alcoholics, low constraint was associated with greater habituation to CS+ probes, and poor differential conditioning on measures of change across trials in SCR to CS+ probes and CS- stimuli. The results suggest that different processes influence levels of constraint in non-alcoholics and alcoholics. The data indicate that low constraint in non-alcoholics is associated with allocating fewer processing resources to potentially significant stimuli, rather than being associated with a specific deficit in aversive conditioning per se.

Acoustic Stimulation↗
PubMed2000

Classically conditioned withdrawal reflex in cerebellar patients. 2. Impaired unconditioned responses.

The study addresses the issue of the role of the cerebellum in human withdrawal-reflex conditioning by comparing data from patients with pure cerebellar diseases (CBL, n = 10) and from cerebellar patients showing additional extracerebellar symptoms (CBL+, n = 10) with those from 11 control subjects (CTRL). During recording sessions, the standard delay-conditioning paradigm with paired-trials was used with tone as the conditioned stimulus (CS). Parameters of the conditioned muscle responses are analyzed in an accompanying paper. Here, we focus on the unconditioned muscle response. A train of current pulses (unconditioned stimulus, US) evoked a lower-limb withdrawal reflex (unconditioned response, UR), which was recorded electromyographically from leg muscles. During the recording sessions with CTRL subjects, UR amplitudes decayed from initially 100% to approximately 50% at the end of the session. This type of decay was clearly less pronounced in the CBL group and minimal in the CBL+ group. Furthermore, the CBL group exhibited UR onsets that were delayed by 20 ms compared with those from CTRL subjects. Although the ranges of measurements characterizing the URs of a given cerebellar patient tested in the paired-trial paradigm overlapped with those of control subjects, the statistically significant differences observed at the group level suggest deficits in the performance of the reflex responses. The delayed URs in patients and the different type of decay of UR amplitudes in repetitively evoked withdrawal reflexes constitute evidence that the cerebellum is critically involved in the control of these UR parameters.

Adult↗