Project summary
Many researchers approach the etiology of trauma-, stressor-, and anxiety-related mental disorders from the
perspective of classical conditioning processes gone awry. According to this view, abnormal associative
relationships between neutral, conditioned stimuli (CSs) and aversive, unconditioned stimuli (USs) underlie
pathological anxiety and result in unusually intense fear memories or fear memories that cannot be properly
extinguished. Recent work has expanded this view by showing that many psychological disorders involving
pathological anxiety are associated with an exaggerated form of the commonly adaptive classical conditioning
phenomenon, stimulus generalization, leading individuals with such disorders to respond with fear and anxiety
to a variety of environmental contexts and cues that should not be threatening. Few studies have been
conducted in humans to better understand the process of fear generalization, and factors that might influence
susceptibility to overgeneralize fear have yet to be assessed. It is well-known that stress, biological sex, and
anxiety-related dispositions of an individual increase one's susceptibility for pathological anxiety and
significantly impact fear learning; thus, it is possible that such factors, alone or in combination, contribute to
clinical anxiety by influencing fear generalization processes. Aim 1 of the present study is to determine the
effects of acute stress and its physiological correlates on fear generalization in human participants. Because
acute stress profoundly impacts cognitive brain areas that underlie generalization, it is predicted that acute
stress will enhance or impair fear generalization, depending on when the stressor is administered relative to
fear learning. Aim 2 is to assess the role of biological sex in fear generalization and acute stress-induced
changes in such processes. Females are more likely than males to develop several psychological disorders
that involve pathological anxiety, and research has consistently reported sex-related differences in fear
learning and stress-induced alterations of fear learning, effects that have been associated with ovarian
hormones. Thus, it is predicted that females will exhibit greater fear generalization than males that will be
impacted differently by stress. It is also hypothesized that the observed effects will correlate with estradiol and
progesterone in females. The final aim of this project (Aim 3) is to evaluate the relationship between childhood
stress, dispositional anxiety, and fear generalization. Early life stress has been repeatedly associated with
altered stress responses and the development of anxiety-related phenotypes, yet the influence of childhood
stress and trait anxiety on fear generalization have yet to be examined. This study will be the first to examine
how several factors that are known to increase susceptibility for trauma-, stressor, and anxiety-related
psychological disorders impact fear generalization in human subjects. The resulting findings will provide
important insight into the etiology of such disorders, which could aid future approaches to their treatment.