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. 2017 Jul;42(8):1640-1646.
doi: 10.1038/npp.2017.17. Epub 2017 Jan 25.

Where There Is Smoke There Is Fear-Impaired Contextual Inhibition of Conditioned Fear in Smokers

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Where There Is Smoke There Is Fear-Impaired Contextual Inhibition of Conditioned Fear in Smokers

Jan Haaker et al. Neuropsychopharmacology. .
Free PMC article

Abstract

The odds-ratio of smoking is elevated in populations with neuropsychiatric diseases, in particular in the highly prevalent diagnoses of post-traumatic stress and anxiety disorders. Yet, the association between smoking and a key dimensional phenotype of these disorders-maladaptive deficits in fear learning and fear inhibition-is unclear. We therefore investigated acquisition and memory of fear and fear inhibition in healthy smoking and non-smoking participants (N=349, 22% smokers). We employed a well validated paradigm of context-dependent fear and safety learning (day 1) including a memory retrieval on day 2. During fear learning, a geometrical shape was associated with an aversive electrical stimulation (classical fear conditioning, in danger context) and fear responses were extinguished within another context (extinction learning, in safe context). On day 2, the conditioned stimuli were presented again in both contexts, without any aversive stimulation. Autonomic physiological measurements of skin conductance responses as well as subjective evaluations of fear and expectancy of the aversive stimulation were acquired. We found that impairment of fear inhibition (extinction) in the safe context during learning (day 1) was associated with the amount of pack-years in smokers. During retrieval of fear memories (day 2), smokers showed an impairment of contextual (safety context-related) fear inhibition as compared with non-smokers. These effects were found in physiological as well as subjective measures of fear. We provide initial evidence that smokers as compared with non-smokers show an impairment of fear inhibition. We propose that smokers have a deficit in integrating contextual signs of safety, which is a hallmark of post-traumatic stress and anxiety disorders.

Figures

Figure 1
Figure 1
(a) Schematic illustration of the context-dependent cue conditioning and extinction paradigm, consisting of a learning phase (day 1) and a retrieval phase 24 h later (day 2). (b) CS specific responses in non-smoking and smoking participants during day 1 (learning) in the danger and safe contexts measured as skin conductance responses (SCRs), (c) subjective fear and (d) US expectancy. (e) Individual amount of cigarette consumption (pack-years) is correlated with conditioned fear responses (CRs) in the safe context during learning on day 1 measured as SCRs, (f) subjective fear and (g) US expectancy.
Figure 2
Figure 2
(a) CS responses during day 2 (retrieval) reveal a context*smoking status (non-smoking vs smoking participants) interaction measured as skin conductance responses (SCRs), (b) subjective fear and (c) US expectancy. (d) During memory retrieval on day 2, smokers show less contextual inhibition of SCRs (CS+: t(346)=3.07, p=0.002; CS−: t(346)=1.54, p=0.14), (e) subjective fear (CS+: t(346)=3.04, p=0.003; CS−: t(346)=3.76, p<0.001) and (f) US expectancy (CS+: t(346)=2.56, p=0.012; CS−: t(346)=2.46, p=0.015). *=p<0.05; **=p<0.01; ***p<0.001. Error bars represent the standard error of the mean.

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