Biomedical subjects

Lee Hogarth

Publications and source records attributed to Lee Hogarth.

6 recordsLinked to original sources

PubMed2006

Drug expectancy is necessary for stimulus control of human attention, instrumental drug-seeking behaviour and subjective pleasure.

BACKGROUND: It has been suggested that drug-paired stimuli (S+) control addictive behaviour by eliciting an explicit mental representation or expectation of drug availability. AIMS: The aim of the present study was to test this hypothesis by determining whether the behavioural control exerted by a tobacco-paired S+ in human smokers would depend upon the S+ eliciting an explicit expectation of tobacco. DESIGN: In each trial, human smokers (n=16) were presented with stimuli for which attention was measured with an eyetracker. Participants then reported their cigarette reward expectancy before performing, or not, an instrumental tobacco-seeking response that was rewarded with cigarette gains if the S+ had been presented or punished with cigarette losses if the S- had been presented. Following training, participants rated the pleasantness of stimuli. RESULTS: The S+ only brought about conditioned behaviour in an aware group (those who expected the cigarette reward outcome when presented with the S+). This aware group allocated attention to the S+, performed the instrumental tobacco-seeking response selectively in the presence of the S+ and rated the S+ as pleasant. No conditioned behaviour was seen in the unaware group (those who did not expect the cigarette reward outcome in the presence of the S+). CONCLUSIONS: Drug-paired stimuli control selective attention, instrumental drug-seeking behaviour and positive emotional state by eliciting an explicit expectation of drug availability.

Adult↗

PubMed2006

Contingency knowledge is necessary for learned motivated behaviour in humans: relevance for addictive behaviour.

AIMS: Many forms of human conditioned behaviour depend upon explicit knowledge of the predictive contingency between stimuli, responses and the reinforcer. However, it remains uncertain whether the conditioning of three key behaviours in drug addiction-selective attention, instrumental drug-seeking behaviour and emotional state--are dependent upon contingency knowledge. To test this possibility, we employed an avoidance procedure to generate rapidly these three forms of conditioned behaviour without incurring the methodological problems of drug conditioning. DESIGN: In two experiments, participants (16 students) were trained on a schedule in which one stimulus (S +) predicted the occurrence of a startling noise, which could be cancelled by performing an instrumental avoidance response. MEASUREMENTS: The allocation of attention to the S + and the rate and probability of the avoidance response in the presence of S + were measured. Following training, participants were tested for their knowledge of the stimulus-noise contingencies arranged in the study and rated the emotional qualities of the stimuli. FINDINGS: Both experiments showed that S + gained control of selective attention, instrumental avoidance behaviour and subjective anxiety, but only in participants who reported explicit knowledge of the Pavlovian contingency between the S + and the startling noise. CONCLUSIONS: The implication of the present findings is that the control of selective attention, instrumental drug-seeking behaviour and emotional state by drug-paired stimuli is mediated by cognitive knowledge of the predictive contingency between the stimulus and the drug.

Adult↗

PubMed2005

Human nicotine conditioning requires explicit contingency knowledge: is addictive behaviour cognitively mediated?

RATIONALE: Two seemingly contrary theories describe the learning mechanisms that mediate human addictive behaviour. According to the classical incentive theories of addiction, addictive behaviour is motivated by a Pavlovian conditioned appetitive emotional response elicited by drug-paired stimuli. Expectancy theory, on the other hand, argues that addictive behaviour is mediated by an expectancy of the drug imparted by cognitive knowledge of the Pavlovian (predictive) contingency between stimuli (S+) and the drug and of the instrumental (causal) contingency between instrumental behaviour and the drug. AIMS AND METHOD: The present paper reviewed human-nicotine-conditioning studies to assess the role of appetitive emotional conditioning and explicit contingency knowledge in mediating addictive behaviour. RESULTS: The studies reviewed here provided evidence for both the emotional conditioning and the expectancy accounts. The first source of evidence is that nicotine-paired S+ elicit an appetitive emotional conditioned response (CR), albeit only in participants who expect nicotine. Furthermore, the magnitude of this emotional state is modulated by nicotine deprivation/satiation. However, the causal status of the emotional response in driving other forms of conditioned behaviour remains undemonstrated. The second source of evidence is that other nicotine CRs, including physiological responses, self-administration, attentional bias and subjective craving, are also dependent on participants possessing explicit knowledge of the Pavlovian contingencies arranged in the experiment. In addition, several of the nicotine CRs can be brought about or modified by instructed contingency knowledge, demonstrating the causal status of this knowledge. CONCLUSIONS: Collectively, these data suggest that human nicotine conditioned effects are mediated by an explicit expectancy of the drug coupled with an appetitive emotional response that reflects the positive biological value of the drug. The implication of this conclusion is that treatments designed to modify the expected value of the drug may prove effective.

Animals↗

PubMed2005

Repeated ethanol exposure and withdrawal impairs human fear conditioning and depresses long-term potentiation in rat amygdala and hippocampus.

BACKGROUND: In rats, repeated episodes of alcohol consumption and withdrawal (RWD) impair fear conditioning to discrete cues. METHODS: Fear conditioning was measured in human binge drinkers as the increased startle response in the presence of a CS+ conditioned to aversive white noise. Secondly, the ability of tone CSs, paired with footshock, to induce c-fos expression, a marker of neuronal activity, in limbic structures subserving emotion was studied in rats. Additionally, consequences of RWD on subsequent induction of long term potentiation (LTP) in external capsule/lateral amygdala and Schaffer collateral/hippocampus CA1 pathways were studied in rat brain slices. RESULTS: Fear conditioning was impaired in young human binge drinkers. The ability of fear-conditioned CSs to increase c-fos expression in limbic brain areas was reduced following RWD, as was LTP induction. Rats conditioned prior to RWD, following RWD showed generalization of conditioned fear from the tone CS+ to a neutral control stimulus, and a novel tone. CONCLUSIONS: Binge-like drinking impairs fear conditioning, reduces LTP, and results in inappropriate generalization of learned fear responses. We propose a mechanism whereby RWD-induced synaptic plasticity reduces capacity for future learning, while allowing unconditioned stimuli access to neuronal pathways underlying conditioned fear.

Adult↗

PubMed2004

Explicit knowledge of stimulus-outcome contingencies and stimulus control of selective attention and instrumental action in human smoking behaviour.

RATIONALE: External stimuli (S+) that reliably signal that addictive drugs are available command the focus of selective attention and control instrumental action that procures the drug. According to incentive salience theory, as the contingency between the S+ and the drug is learned the magnitude of attentional orienting towards the S+ increases. By contrast, alternative theories propose that processing of the S+ becomes more efficient with training such that the measured attentional orienting response elicited by the S+ decreases. OBJECTIVES: The aim of the present study was to prompt half of participants to acquire explicit knowledge of the stimulus-reinforcer contingencies arranged in training, to examine the impact of this manipulation on the magnitude of attentional orienting towards the S+. METHODS: Smokers (n=32) completed an instrumental discrimination training procedure in which a set of stimuli were established as differential predictors that an instrumental response would yield tobacco-smoke reinforcement. During training, attention for the stimuli and performance of the instrumental tobacco-seeking response were measured in parallel. One group (n=16) was prompted to develop explicit knowledge of the discriminative contingencies in training whereas another group (n=16) underwent discrimination training without prompting. RESULTS: The prompted group reported accurate knowledge of the contingencies and showed no attentional orienting response towards the S+. By contrast, the unprompted group reported inaccurate knowledge of the contingencies and showed an attentional orienting response towards the S+. The S+ appeared to control the instrumental tobacco-seeking response in both groups equally. CONCLUSIONS: The results suggest that attention for drug paired S+ is associated with the process of learning about the relationship between those cues and the drug.

Attention↗

PubMed2003

Discriminative stimuli that control instrumental tobacco-seeking by human smokers also command selective attention.

RATIONALE: Incentive salience theory states that acquired bias in selective attention for stimuli associated with tobacco-smoke reinforcement controls the selective performance of tobacco-seeking and tobacco-taking behaviour. OBJECTIVES: To support this theory, we assessed whether a stimulus that had acquired control of a tobacco-seeking response in a discrimination procedure would command the focus of visual attention in a subsequent test phase. METHODS: Smokers received discrimination training in which an instrumental key-press response was followed by tobacco-smoke reinforcement when one visual discriminative stimulus (S+) was present, but not when another stimulus (S-) was present. The skin conductance response to the S+ and S- assessed whether Pavlovian conditioning to the S+ had taken place. In a subsequent test phase, the S+ and S- were presented in the dot-probe task and the allocation of the focus of visual attention to these stimuli was measured. RESULTS: Participants learned to perform the instrumental tobacco-seeking response selectively in the presence of the S+ relative to the S-, and showed a greater skin conductance response to the S+ than the S-. In the subsequent test phase, participants allocated the focus of visual attention to the S+ in preference to the S-. Correlation analysis revealed that the visual attentional bias for the S+ was positively associated with the number of times the S+ had been paired with tobacco-smoke in training, the skin conductance response to the S+ and with subjective craving to smoke. Furthermore, increased exposure to tobacco-smoke in the natural environment was associated with reduced discrimination learning. CONCLUSIONS: These data demonstrate that discriminative stimuli that signal that tobacco-smoke reinforcement is available acquire the capacity to command selective attentional and elicit instrumental tobacco-seeking behaviour.

Adult↗