Animal studies have shown that estrogens exert important influence on the acquisition and extinction of conditioned fear, however, the gonadal hormone regulation of fear in human is not known. The purpose of the present study is to examine effects of female menstrual phases on the conditioned fear acquisition and extinction.
Twenty female college students in luteal phase and 20 female college students in menses phase participated in the experiment. They were exposed to three conditions: 1) predictable aversive stimuli were signaled by a cue; 2) aversive stimuli were administered unpredictably; 3) no aversive stimuli were anticipated. Aversive unconditioned stimulus (US) expectancy was used to assess anxious responses to the threat cue and to contexts associated with each condition.
The results showed that, at the acquisition stage, females in luteal phase (FL) showed higher US expectance for the conditioned context fear in N and P context than females in menses phase (FM); at the extinction stage, FL had a significantly higher US expectancy in N and P context compared to FM. In other words, the females of luteal phase acquired the conditioned context fear response more effectively and extinguished more slowly than females of menses phase.
These data suggest that menstrual cycle can possibly influence the conditioned context fear responses in females. This phenomenon suggests that the gonadal hormone level of luteal phase may affect fear regulation.