Fear generalization, the generalization of fear to innocuous stimuli, is a characteristic component of pathological anxiety. For example, after returning from war, a person might begin to experience fear in response to the sound of fireworks, a stimulus typically regarded as safe. When excessive, “overgeneralization” serves as a core feature of fear and anxiety-related disorders, such as PTSD. The present collection of studies sought to investigate the neural correlates and temporal dynamics of fear generalization in humans.
The first study sought to investigate the causal role of the ventromedial prefrontal cortex (vmPFC) and hippocampus in the generalization of fear. Contrary to hypotheses, individuals with focal damage to the vmPFC (N=8) or hippocampus (N=12) did not demonstrate significantly increased fear generalization relative to individuals with brain damage outside of these regions (N=16) or normal comparison participants (N=20). Potential explanations for this finding are explored. The second study sought to investigate the time course of fear generalization in humans. Participants (N = 107) completed a fear generalization task over the course of two sessions. Results indicate that fear generalization significantly increased as the duration of time between training and testing increased. This suggests that a stimulus may elicit a generalized fear response at one arbitrarily selected time point, but not another. This study establishes a novel paradigm that can be used in future work to investigate changes in the neural correlates of fear generalization over time.
Fear generalization is found across an array of anxiety disorders, making it a compelling area of study. The present work highlights the dynamic nature of fear generalization in humans. Further, the present study leads to a number of questions for future research.