Anxiety disorders are the most prevalent subgroup of mental disorders in most western societies, with nearly a 1 in 3 lifetime prevalence in the US. Psychologically, anxiety can be defined as a prolonged state of apprehension elicited by an uncertain or unpredictable prospective threat. While the term “anxiety” is often used interchangeably with “fear,” more precisely, fear describes the phasic response to an immediate and identifiable threat.
This subtle psychological distinction between fear and anxiety is thought to be paralleled by two partially segregated neural circuits that support these divergent responses. The amygdala putatively underlies phasic responses to explicit and imminent threats, supporting feelings of fear. By comparison, the bed nucleus of the stria terminalis (BNST) — an often overlooked basal forebrain region comprising part of the extended amygdala — is thought to mediate more sustained responses to unpredictable, ambiguous or diffuse threats, thus underlying persistent states of anticipation or hypervigilance, and promoting feelings of anxiety. However, newer perspectives suggest that both the amygdala and BNST exhibit similar functional profiles in response to a variety of aversive threats.
Therefore, using high-resolution fMRI (1.5 mm3), this work aims to investigate the functional activation profiles and connectivity patterns of the amygdala and BNST during certain and predictable threat (fear), as well as uncertain and unpredictable threat (anxiety). Differentiating these two processes has extremely broad and important implications for brain and psychological theory and for the development of more targeted treatments for anxiety disorders.