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- Fredrikson, Mats, et al.
(författare)
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Different genetic factors underlie fear conditioning and episodic memory
- 2015
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Ingår i: Psychiatric Genetics. - 0955-8829 .- 1473-5873. ; 25:4, s. 155-162
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveFear conditioning seems to account for the acquisition of post-traumatic stress disorder, whereas conscious recall of events in aftermath of trauma reflects episodic memory. Studies show that both fear conditioning and episodic memory are heritable, but no study has evaluated whether they reflect common or separate genetic factors. To this end, we studied episodic memory and fear conditioning in 173 healthy twin pairs using visual stimuli predicting unconditioned electric shocks.MethodsFear conditioning acquisition and extinction was determined using conditioned visual stimuli predicting unconditioned mild electric shocks, whereas electrodermal activity served as the fear learning index. Episodic memory was evaluated using cued recall of pictorial stimuli unrelated to conditioning. We used multivariate structural equation modeling to jointly analyze memory performance and acquisition as well as extinction of fear conditioning.ResultsBest-fit twin models estimated moderate genetic loadings for conditioning and memory measures, with no genetic covariation between them.ConclusionIndividual differences in fear conditioning and episodic memory reflect distinct genetically influenced processes, suggesting that the genetic risk for learning-induced anxiety disorders includes at least two memory-related genetic factors. These findings are consistent with the facts that the two separate learning forms are distant in their evolutionary development, involve different brain mechanisms, and support that genetically independent memory systems are pivotal in the development and maintenance of syndromes related to fear learning.
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| 2. |
- Hettema, John M, et al.
(författare)
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A twin study of the genetics of fear conditioning.
- 2003
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Ingår i: Arch Gen Psychiatry. - : American Medical Association (AMA). - 0003-990X. ; 60:7, s. 702-8
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Tidskriftsartikel (refereegranskat)abstract
- Fear conditioning is a traditional model for the acquisition of fears and phobias. Studies of the genetic architecture of fear conditioning may inform gene-finding strategies for anxiety disorders. The objective of this study was to determine the genetic and environmental sources of individual differences in fear conditioning by means of a twin sample. METHODS: Classic fear conditioning data were experimentally obtained from 173 same-sex twin pairs (90 monozygotic and 83 dizygotic). Sequences of evolutionary fear-relevant (snakes and spiders) and fear-irrelevant (circles and triangles) pictorial stimuli served as conditioned stimuli paired with a mild electric shock serving as the unconditioned stimulus. The outcome measure was the electrodermal skin conductance response. We applied structural equation modeling methods to the 3 conditioning phases of habituation, acquisition, and extinction to determine the extent to which genetic and environmental factors underlie individual variation in associative and nonassociative learning. RESULTS: All components of the fear conditioning process in humans demonstrated moderate heritability, in the range of 35% to 45%. Best-fitting multivariate models suggest that 2 sets of genes may underlie the trait of fear conditioning: one that most strongly affects nonassociative processes of habituation that also is shared with acquisition and extinction, and a second that appears related to associative fear conditioning processes. In addition, these data provide tentative evidence of differences in heritability based on the fear relevance of the stimuli. CONCLUSION: Genes represent a significant source of individual variation in the habituation, acquisition, and extinction of fears, and genetic effects specific to fear conditioning are involved.
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| 3. |
- Hettema, John M., et al.
(författare)
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The genetic covariation between fear conditioning and self-report fears
- 2008
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Ingår i: Biological Psychiatry. - : Elsevier BV. - 0006-3223 .- 1873-2402. ; 63:6, s. 587-593
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Tidskriftsartikel (refereegranskat)abstract
- Background: Fear conditioning is a traditional model for the acquisition of phobias, whereas behavioral therapies use processes underlying extinction to treat phobic and other anxiety disorders. Furthermore, fear conditioning has been proposed as an endophenotype for genetic studies of anxiety disorders. Although prior studies have demonstrated that fear conditioning and self-report fears are heritable, no studies have determined whether they share a common genetic basis. Methods: We obtained fear conditioning data from 173 twin pairs from the Swedish Twin Registry who also provided self-report ratings of 16 common fears. With multivariate structural equation modeling, we analyzed factor-derived scores for the subjective fear ratings together with the electrophysiologic skin conductance responses during habituation, acquisition, and extinction to determine the extent of their genetic covariation. Results: Phenotypic correlations between experimental and self-report fear measures were modest and, counter-intuitively, negative (i.e., subjects who reported themselves as more fearful had smaller electrophysiologic responses). Best-fit models estimated a significant (negative) genetic correlation between them, although genetic factors underlying fear conditioning accounted for only 9% of individual differences in self-report fears. Conclusions: Experimentally derived fear conditioning measures share only a small portion of the genetic factors underlying individual differences in subjective fears, cautioning against relying too heavily on the former as an endophenotype for genetic studies of phobic disorders.
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