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In emotional learning tasks, sex differences, stress effects and an interaction of these two moderators have often been observed. The sex hormones estradiol (E2) and progesterone (P4) vary over the menstrual cycle. We tested groups with different sex hormone status: 39 men, 30 women in the luteal phase (LU, high E2+P4) and 29 women taking oral contraceptives (OC, low E2+P4). They received either 30 mg cortisol or placebo prior to instructed differential fear conditioning consisting of neutral conditioned stimuli (CS) and an electrical stimulation (unconditioned stimulus; UCS). One figure (CS+) was paired with the UCS, the other figure (CS-) never. During extinction, no electrical stimulation was administered. Regarding fear acquisition, results showed higher skin conductance and higher brain responses to the CS+ compared to the CS- in several structures that were not modulated by cortisol or sex hormones. However, OC women exhibited higher CS+/CS- differentiations than men and LU women in the amygdala, thalamus, anterior cingulate and ventromedial prefrontal cortex during extinction. The suppression of endogenous sex hormones by OC seems to alter neuronal correlates of extinction. The observation that extinction is influenced by the current sex hormone availability is relevant for future studies and might also be clinically important.
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The ability to detect and learn contingencies between fearful stimuli and their predictive cues is an important capacity to cope with the environment. Contingency awareness refers to the ability to verbalize the relationships between conditioned and unconditioned stimuli. Although there is a heated debate about the influence of contingency awareness on conditioned fear responses, neural correlates behind the formation process of contingency awareness have gained only little attention in human fear conditioning. Recent animal studies indicate that the ventral striatum (VS) could be involved in this process, but in human studies the VS is mostly associated with positive emotions. To examine this question, we reanalyzed four recently published classical fear conditioning studies (n = 117) with respect to the VS at three distinct levels of contingency awareness: subjects, who did not learn the contingencies (unaware), subjects, who learned the contingencies during the experiment (learned aware) and subjects, who were informed about the contingencies in advance (instructed aware). The results showed significantly increased activations in the left and right VS in learned aware compared to unaware subjects. Interestingly, this activation pattern was only found in learned but not in instructed aware subjects. We assume that the VS is not involved when contingency awareness does not develop during conditioning or when contingency awareness is unambiguously induced already prior to conditioning. VS involvement seems to be important for the transition from a contingency unaware to a contingency aware state. Implications for fear conditioning models as well as for the contingency awareness debate are discussed.
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Team
- Vaitl (2)
Eintragsart
Sprache
Thema
- Hydrocortisone/pharmacology
- Adolescent (1)
- Adult (2)
- Amygdala/physiology (1)
- Awareness/physiology (1)
- Basal Ganglia/blood supply/drug effects/*physiology (1)
- Brain Mapping (1)
- Conditioning, Classical/drug effects/*physiology (1)
- Conditioning, Psychological/*physiology (1)
- Contraceptives, Oral (1)
- Databases, Factual/statistics & numerical data (1)
- Extinction, Psychological/*drug effects/physiology (1)
- *Fear/drug effects (1)
- Fear/*physiology (1)
- Female (2)
- Gonadal Steroid Hormones/*pharmacology (1)
- Humans (2)
- Magnetic Resonance Imaging/methods (1)
- Male (2)
- Models, Statistical (1)
- Oxygen/blood (1)
- Young Adult (2)